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  • 1.
    Andersson, Erik
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Björklund, Glenn
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Swedish Olympic Committee, Stockholm, Sweden.
    Ørtenblad, Niels
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Department of Sports Science and Clinical Biomechanics, SDU Muscle Research Cluster, University of Southern Denmark, Odense, Denmark.
    Energy system contributions and determinants of performance in sprint cross-country skiing2017In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 27, no 4, p. 385-398Article in journal (Refereed)
    Abstract [en]

    To improve current understanding of energy contributions and determinants of sprint-skiing performance, 11 well-trained male cross-country skiers were tested in the laboratory for VO2max , submaximal gross efficiency (GE), maximal roller skiing velocity, and sprint time-trial (STT) performance. The STT was repeated four times on a 1300-m simulated sprint course including three flat (1°) double poling (DP) sections interspersed with two uphill (7°) diagonal stride (DS) sections. Treadmill velocity and VO2 were monitored continuously during the four STTs and data were averaged. Supramaximal GE during the STT was predicted from the submaximal relationships for GE against velocity and incline, allowing computation of metabolic rate and O2 deficit. The skiers completed the STT in 232 ± 10 s (distributed as 55 ± 3% DP and 45 ± 3% DS) with a mean power output of 324 ± 26 W. The anaerobic energy contribution was 18 ± 5%, with an accumulated O2 deficit of 45 ± 13 mL/kg. Block-wise multiple regression revealed that VO2 , O2 deficit, and GE explained 30%, 15%, and 53% of the variance in STT time, respectively (all P < 0.05). This novel GE-based method of estimating the O2 deficit in simulated sprint-skiing has demonstrated an anaerobic energy contribution of 18%, with GE being the strongest predictor of performance.

  • 2.
    Andersson, Erik
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Ørtenblad, Niels
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Björklund, Glenn
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Energy contributions and pacing strategies of elite XC skiers during sprint skiing2016Conference paper (Refereed)
    Abstract [en]

    INTRODUCTION: At present, knowledge regarding energy contributions and pacing strategies during successive sprint time-trials (STTs) in cross-country (XC) skiing is limited and, therefore, the current study was designed to examine these parameters. The results shown have recently been published elsewhere (Andersson et al., 2016).METHODS: Ten well-trained male XC skiers performed four self-paced 1300-m STTs on a treadmill, separated by 45 min of recovery. The simulated STT course was divided into three flat (1°) sections (S1, S3 and S5) involving the double poling (DP) sub-technique interspersed with two uphill (7°) sections (S2 and S4) involving the diagonal stride (DS) sub-technique. Treadmill velocity and VO2 were monitored continuously and technique-specific gross efficiency (based on submaximal pre-tests) was used to estimate anaerobic energy production.RESULTS & DISCUSSION: The average STT performance time was 229 ± 9 s and the aerobic energy contribution was 82 ± 5%. A positive pacing strategy was used during all STTs, with 3-9% more time spent on the second half of the course (P < 0.05). In addition, the pacing strategy was regulated to the terrain, with substantially higher (~30%) metabolic rates, due to primarily higher anaerobic energy production, for uphill compared with flat skiing (P < 0.05). The individually fastest STT was more aggressively paced compared to the slowest STT (P < 0.05), which resulted in a higher O2 deficit rate (13 ± 4 versus 11 ± 4 mL/kg/min, P < 0.05), while the VO2 was similar (both 52 ± 3 mL/kg/min). These findings emphasise the importance of a fast start. The within-athlete coefficient of variation (CV) in performance time, VO2 and O2 deficit were 1.3 ± 0.4%, 1.4 ± 0.9% and 11.2 ± 4.9%, respectively, with the CV in O2 deficit explaining 69% of the CV in performance. The pacing strategies were highly consistent, with an average CV in speed of 3.4%.CONCLUSION: The fastest STT was characterized by more aggressive pacing and a greater anaerobic energy production. Although the individual performance time during the four STTs was highly consistent, the small within-athlete variability in performance was related to variations in anaerobic energy production.

  • 3.
    Andersson, Erik
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Ørtenblad, Niels
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Björklund, Glenn
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Metabolic responses and pacing strategies during successive sprint skiing time trials2016In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 48, no 12, p. 2544-2554Article in journal (Refereed)
    Abstract [en]

    PURPOSE: To examine the metabolic responses and pacing strategies during the performance of successive sprint time trials (STTs) in cross-country skiing. METHODS: Ten well-trained male cross-country skiers performed four self-paced 1300-m STTs on a treadmill, each separated by 45 min of recovery. The simulated STT course was divided into three flat (1°) sections (S1, S3 and S5) involving the double poling sub-technique interspersed with two uphill (7°) sections (S2 and S4) involving the diagonal stride sub-technique. Treadmill velocity and V˙O2 were monitored continuously and gross efficiency was used to estimate the anaerobic energy supply. RESULTS: The individual trial-to-trial variability in STT performance time was 1.3%, where variations in O2 deficit and V˙O2 explained 69% (P < 0.05) and 11% (P > 0.05) of the variation in performance. The first and last STTs were equally fast (228 ± 10 s), and ~ 1.3% faster than the second and the third STTs (P < 0.05). These two fastest STTs were associated with a 14% greater O2 deficit (P < 0.05), while the average V˙O2 was similar during all four STTs (86 ± 3% of V˙O2max). Positive pacing was used throughout all STTs, with significantly less time spent on the first than second course half. In addition, metabolic rates were substantially higher (~_30%) for uphill than for flat skiing, indicating that pacing was regulated to the terrain. CONCLUSIONS: The fastest STTs were characterized primarily by a greater anaerobic energy production, which also explained 69% of the individual variation in performance. Moreover, the skiers employed positive pacing and a variable exercise intensity according to the course profile, yielding an irregular distribution of anaerobic energy production.

  • 4.
    Andersson, Erik
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Pellegrini, B
    Stöggl, Thomas
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Sandbakk, Ø
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    COMPARISONS BETWEEN HERRINGBONE AND DIAGONAL STRIDE TECHNIQUES IN CROSS-COUNTRY SKIING2012In: / [ed] Meeusen, R., Duchateau, J., Roelands, B., Klass, M., De Geus, B., Baudry, S., Tsolakidis, E., 2012, p. 77-77Conference paper (Refereed)
  • 5.
    Andersson, Erik
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Pellegrini, Barbara
    CeRiSM, Research Center for Sport, Mountain and Health, Rovereto, Italy.
    Sandbakk, Öyvind
    Centre for Elite Sports Research, Norwegian University of Science and Technology, Trondheim, Norway .
    Stöggl, Thomas
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Department of Sport Science and Kinesiology, University of Salzburg, Salzburg, Austria .
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Swedish Olympic Committee, Stockholm, Sweden.
    The effects of skiing velocity on mechanical aspects of diagonal cross-country skiing2014In: Sports Biomechanics, ISSN 1476-3141, E-ISSN 1752-6116, Vol. 13, no 3, p. 267-284Article in journal (Refereed)
    Abstract [en]

    Cycle and force characteristics were examined in 11 elite male cross-country skiers using the diagonal stride technique while skiing uphill (7.5 degrees) on snow at moderate (3.5 +/- 0.3m/s), high (4.5 +/- 0.4m/s), and maximal (5.6 +/- 0.6m/s) velocities. Video analysis (50Hz) was combined with plantar (leg) force (100Hz), pole force (1,500Hz), and photocell measurements. Both cycle rate and cycle length increased from moderate to high velocity, while cycle rate increased and cycle length decreased at maximal compared to high velocity. The kick time decreased 26% from moderate to maximal velocity, reaching 0.14s at maximal. The relative kick and gliding times were only altered at maximal velocity, where these were longer and shorter, respectively. The rate of force development increased with higher velocity. At maximal velocity, sprint-specialists were 14% faster than distance-specialists due to greater cycle rate, peak leg force, and rate of leg force development. In conclusion, large peak leg forces were applied rapidly across all velocities and the shorter relative gliding and longer relative kick phases at maximal velocity allow maintenance of kick duration for force generation. These results emphasise the importance of rapid leg force generation in diagonal skiing.

  • 6.
    Andersson, Erik
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Pellegrini, Barbara
    Stöggl, Thomas
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Sandbakk, Øyvind
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    MECHANICS OF VELOCITY ADAPTATION IN DIAGONAL SKIING2012In: / [ed] Anni Hakkarainen, Stefan Lindinger and Vesa Linnamo, 2012, p. 62-62Conference paper (Refereed)
  • 7.
    Andersson, Erik
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Stöggl, Thomas
    University of Salzburg.
    Pellegrini, Barbara
    University of Verona.
    Sandbakk, Oyvind
    NTNU, Trondheim, Norge.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Biomechanical comparison of different uphill techniques in the classical style cross-country skiing2010In: Proceedings for the fifth international conference on Science and Skiing / [ed] Erich Mueller, Salzburg, Austria: Meyer & Meyer Sport, 2010, p. 46-Conference paper (Refereed)
  • 8.
    Andersson, Erik
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Stöggl, Thomas
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Pellegrini, Barbara
    CeRiSM Research Center for Sport, Mountain and Health University of Verona Rovereto Italy.
    Sandbakk, Øyvind
    Department of Human Movement Science Norwegian University of Science and Technology Trondheim Norway.
    Ettema, Gertjan
    Department of Human Movement Science Norwegian University of Science and Technology Trondheim Norway.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Biomechanical analysis of the herringbone technique as employed by elite cross-country skiers2014In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 24, no 3, p. 542-552Article in journal (Refereed)
    Abstract [en]

    This investigation was designed to analyse the kinematics and kinetics of cross-country skiing at different velocities with the herringbone technique on a steep incline. Eleven elite male cross-country skiers performed this technique at maximal, high, and moderate velocities on a snow-covered 15° incline. They positioned their skis laterally (25 to 30°) with a slight inside tilt and planted their poles laterally (8 to 12°) with most leg thrust force exerted on the inside forefoot. Although 77% of the total propulsive force was generated by the legs, the ratio between propulsive and total force was approximately fourfold higher for the poles. The cycle rate increased with velocity (1.20 to 1.60 Hz), whereas the cycle length increased from moderate up to high velocity, but then remained the same at maximal velocity (2.0 to 2.3 m). In conclusion, with the herringbone technique, the skis were angled laterally without gliding, with the forces distributed mainly on the inside forefoot to enable grip for propulsion. The skiers utilized high cycle rates with major propulsion by the legs, highlighting the importance of high peak and rapid generation of leg forces.

  • 9.
    Andersson, Erik
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Supej, Matej
    University of Ljubljana, Ljubljana, Slovenien.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Analysis of a sprint qualification round in cross-country skiing using a differential global navigation system2009In: Proceedings of the 14th Annual Congress of European College of Sports Science / [ed] Loland, S., Bø, K., Fasting, K., Hallén, J., Ommundsen, Y., Roberts, G., Tsolakidis, E., Oslo: Gamlebyen Grafiske AS , 2009Conference paper (Refereed)
  • 10.
    Andersson, Erik
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Supej, Matej
    Faculty of Sport, University of Ljubljana, Ljubljana, Slovenia.
    Sandbakk, Oyvind
    Human Movement Science Programme, Norwegian University of Science and Technology, Trondheim, Norway.
    Sperlich, Billy
    Institute of Training Science and Sport Informatics, German Sport University Cologne, Germany .
    Stöggl, Thomas
    Department of Sport Science and Kinesiology, University of Salzburg, Salzburg, Austria.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Analysis of sprint cross-country skiing using a differential global navigation satellite system2010In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 110, no 3, p. 585-595Article in journal (Refereed)
    Abstract [en]

    The purpose was to examine skiing velocities, gear choice (G2-7) and cycle rates during a skating sprint time trial (STT) and their relationships to performance, as well as to examine relationships between aerobic power, body composition and maximal skiing velocity versus STT performance. Nine male elite cross-country skiers performed three tests on snow: (1) Maximum velocity test (Vmax) performed using G3 skating, (2) Vmax test performed using double poling (DP) technique and (3) a STT over 1,425 m. Additional measurements of VO2max during roller skiing and body composition using iDXA were made. Differential global navigation satellite system data were used for position and velocity and synchronized with video during STT. The STT encompassed a large velocity range (2.9-12.9 m s-1) and multiple transitions (21-34) between skiing gears. Skiing velocity in the uphill sections was related to gear selection between G2 and G3. STT performance was most strongly correlated to uphill time (r = 0.92, P < 0.05), the percentage use of G2 (r = -0.72, P < 0.05), and DP Vmax (r = -0.71, P < 0.05). The velocity decrease in the uphills from lap 1 to lap 2 was correlated with VO2max (r = -0.78, P < 0.05). Vmax in DP and G3 were related to percent of racing time using G3. In conclusion, the sprint skiing performance was mainly related to uphill performance, greater use of the G3 technique, and higher DP and G3 maximum velocities. Additionally, VO2max was related to the ability to maintain racing velocity in the uphills and lean body mass was related to starting velocity and DP maximal speed.

  • 11.
    Andersson, Erik
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Willis, Sarah J.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Ørtenblad, Niels
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Energy System Contributions And Determinants Of Performance In Classical Sprint Cross-Country Skiing2014In: Proceedings for the 19th ECCS in Amsterdam, The Netherlands, 2014Conference paper (Refereed)
  • 12.
    Apro, William
    et al.
    Swedish School of Sport & Health Sciences, Stockholm, Sweden.
    Moberg, Marcus
    Swedish School of Sport & Health Sciences, Stockholm, Sweden.
    Hamilton, D. Lee
    University of Stirling, Scotland.
    Ekblom, Bjorn
    Swedish School of Sport & Health Sciences, Stockholm, Sweden.
    Rooyackers, Olav
    Karolinska Inst, Dept Clin Sci Intervent & Technol, Stockholm, Sweden .
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Blomstrand, Eva
    Swedish Sch Sport & Hlth Sci, Astrand Lab, SE-11486 Stockholm, Sweden ; Karolinska Inst, Dept Physiol & Pharmacol, Stockholm, Sweden.
    Leucine does not affect mechanistic target of rapamycin complex 1 assembly but is required for maximal ribosomal protein s6 kinase 1 activity in human skeletal muscle following resistance exercise2015In: The FASEB Journal, ISSN 0892-6638, E-ISSN 1530-6860, Vol. 29, no 10, p. 4358-4373Article in journal (Refereed)
    Abstract [en]

    We examined how the stimulatory effect of leucine on the mechanistic target of rapamycin complex 1 (mTORC1) pathway is affected by the presence of the remaining essential amino acids (EAAs). Nine male subjects performed resistance exercise on 4 occasions and were randomly supplied EAAs with leucine, EAAs without leucine (EAA-Leu), leucine alone, or flavored water (placebo; control). Muscle biopsies were taken from the vastus lateralis before and 60 and 90 min after exercise. Biopsies were analyzed for protein phosphorylation, kinase activity, protein-protein interactions, amino acid concentrations, and tracer incorporation. Leucine alone stimulated ribosomal protein s6 kinase 1 (S6K1) phosphorylation similar to 280% more than placebo and EAA-Leu after exercise. Moreover, this response was enhanced by 60-75% after intake of EAAs compared with that of leucine alone (P < 0.05). Kinase activity of S6K1 reflected that of S6K1 phosphorylation; 60 min after exercise, the activity was elevated 3.3- and 4.2-fold with intake of leucine alone and with EAAs, respectively (P < 0.05). The interaction between mammalian target of rapamycin and regulatory-associated protein of mammalian target of rapamycin was unaltered in response to both resistance exercise and amino acid provision. Leucine alone stimulates mTORC1 signaling, although this response is enhanced by other EAAs and does not appear to be caused by alterations inmTORC1 assembly.

  • 13.
    Apro, William
    et al.
    Swedish Sch Sport & Hlth Sci, Astrand Lab, SE-11486 Stockholm, Sweden.
    Moberg, Marcus
    Swedish Sch Sport & Hlth Sci, Astrand Lab, SE-11486 Stockholm, Sweden.
    Hamilton, D. Lee
    Univ Stirling, Hlth & Exercise Sci Res Grp, Stirling FK9 4LA, Scotland.
    Ekblom, Björn
    Swedish Sch Sport & Hlth Sci, Astrand Lab, SE-11486 Stockholm, Sweden.
    van Hall, Gerrit
    Univ Copenhagen, Rigshosp, Dept Biomed Sci, DK-1168 Copenhagen, Denmark.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Blomstrand, Eva
    Swedish Sch Sport & Hlth Sci, Astrand Lab, SE-11486 Stockholm, Sweden.
    Resistance exercise-induced S6K1 kinase activity is not inhibited in human skeletal muscle despite prior activation of AMPK by high-intensity interval cycling2015In: American Journal of Physiology. Endocrinology and Metabolism, ISSN 0193-1849, E-ISSN 1522-1555, Vol. 308, no 6, p. E470-E481Article in journal (Refereed)
    Abstract [en]

    Combining endurance and strength training in the same session has been reported to reduce the anabolic response to the latter form of exercise. The underlying mechanism, based primarily on results from rodent muscle, is proposed to involve AMPK-dependent inhibition of mTORC1 signaling. This hypothesis was tested in eight trained male subjects who in randomized order performed either resistance exercise only (R) or interval cycling followed by resistance exercise (ER). Biopsies taken from the vastus lateralis before and after endurance exercise and repeatedly after resistance exercise were assessed for glycogen content, kinase activity, protein phosphorylation, and gene expression. Mixed muscle fractional synthetic rate was measured at rest and during 3 h of recovery using the stable isotope technique. In ER, AMPK activity was elevated immediately after both endurance and resistance exercise (similar to 90%, P < 0.05) but was unchanged in R. Thr(389) phosphorylation of S6K1 was increased severalfold immediately after exercise (P < 0.05) in both trials and increased further throughout recovery. After 90 and 180 min recovery, S6K1 activity was elevated (similar to 55 and similar to 110%, respectively, P < 0.05) and eukaryotic elongation factor 2 phosphorylation was reduced (similar to 55%, P < 0.05) with no difference between trials. In contrast, markers for protein catabolism were differently influenced by the two modes of exercise; ER induced a significant increase in gene and protein expression of MuRF1 (P < 0.05), which was not observed following R exercise only. In conclusion, cycling-induced elevation in AMPK activity does not inhibit mTOR complex 1 signaling after subsequent resistance exercise but may instead interfere with the hypertrophic response by influencing key components in protein breakdown.

  • 14.
    Apró, William
    et al.
    Swedish Sch Sport & Hlth Sci, Stockholm, Sweden.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Rooyackers, Olav
    Karolinska Univ Hosp, Huddinge, Sweden.
    Blomstrand, Eva
    Swedish Sch Sport & Hlth Sci, Stockholm, Sweden.
    Is leucine induced p70S6 kinase phosphorylation following resistance exercise dependent on elevated phenylalanine levels in human skeletal muscle?2010In: The FASEB Journal, ISSN 0892-6638, E-ISSN 1530-6860, Vol. 24, p. lb273-Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to investigate the specific role of

    leucine in the stimulation of the mammalian target of rapamycin

    signalling pathway. Six male subjects performed four heavy

    resistance exercise sessions, each separated by approximately one

    week. Subjects were randomly supplemented with one of four

    drinks: placebo (flavored water), leucine or essential amino acids

    (EAA) with and without leucine. Immediately following each

    exercise session, four subjects were infused with a flooding dose of

    L-[2H5] phenylalanine (Inf) while two subjects served as controls

    (Ctrl). Muscle biopsies were taken before and one hour after

    exercise. In the Ctrl group, resistance exercise resulted in a

    substantial increase (45-fold) in p70 kinase phosphorylation

    when all EAA were ingested, whereas ingestion of leucine alone

    had no greater effect than that of placebo. In the Inf group,

    however, ingestion of leucine alone and EAA increased p70

    phosphorylation to a similar extent (35-fold). The divergent

    signalling response in the two groups suggests that leucine alone is

    insufficient to increase p70

    phosphorylation. Indeed, in the Inf

    group, there was a strong correlation (r=0.91) between

    p70 phosphorylation and the product of muscle leucine and

    phenylalanine levels. These results suggest that the stimulatory

    effect of leucine on p70 phosphorylation is dependent on

    elevated muscle phenylalanine levels. Supported by the Swedish

    National Centre for Research in Sports

     

  • 15.
    Apró, William
    et al.
    Swedish School of Sport and Health Sciences, Stockholm, Sweden.
    Moberg, Marcus
    Swedish School of Sport and Health Sciences, Stockholm, Sweden.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Blomstrand, Eva
    Swedish School of Sport and Health Sciences, Stockholm, Sweden.
    Amino Acid-induced S6K1 Activity in Human Skeletal Muscle is Mediated By Increased mTor/Rheb Interaction: 128 June 1, 11: 15 AM - 11: 30 AM2016In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 48, no 5 Suppl 1, p. 17-Article in journal (Refereed)
    Abstract [en]

    Cell culture studies have shown that amino acids activate mTORC1 signaling by increasing the interaction between mTOR and its essential activator Rheb. However, the existence of this mechanism in human skeletal muscle remains to be determined.

    PURPOSE: To determine if increased mTORC1 signaling in response to amino acids in human skeletal muscle is due to an increased interaction between mTOR and Rheb.

    METHODS: Eight well trained men performed resistance exercise on two separate occasions. In connection with the exercise, subjects were supplemented with flavored water (Pla) and essential amino acids (EAA) in a double-blind, randomized cross-over design. Muscle biopsies were taken in the vastus lateralis muscle before, immediately after and 90 and 180 min post exercise. Activity of the mTORC1 pathway was assessed by a radiolabeled in-vitro kinase assay for its immediate downstream target S6K1. Protein-protein interactions were determined by western blot following co-immunoprecipitation of mTOR with Rheb. Co-immunoprecipitation was performed on pooled muscle samples from three of the eight subjects.

    RESULTS: Activity of S6K1 remained unchanged immediately after exercise in both trials. However, at 90 min post exercise, S6K1 activity increased by approximately 2- and 8-fold (p<0.05) from baseline the Pla and EAA trials, respectively. At the 180 min time point, S6K1 activity remained elevated in both trials being approx. 3-fold higher in the Pla trial and 5-fold higher (p<0.05) in the EAA trial. The fold-change in mTOR and Rheb interaction largely resembled the activity pattern of S6K1 in both trials; in the Pla trial the fold-change was 0.9, 1.3 and 1.4 while in the EAA trial the fold-change was 1.6, 2.9 and 1.9 immediately after, 90 min after and 180 min after exercise, respectively.

    CONCLUSIONS: The large increase in S6K1 activity following EAA intake appears to be mediated by an increased interaction between mTOR and its proximal activator Rheb. This is the first time this mechanism has been demonstrated in human skeletal muscle.

  • 16.
    Azzinnari, M
    et al.
    University of Las Palmas, Spain.
    Martin-Rincon, M
    University of Las Palmas, Spain.
    Juan-Habib, J
    University of Las Palmas, Spain.
    Gelabert-Rebato, M
    University of Las Palmas, Spain.
    Calbet, JAL
    University of Las Palmas, Spain.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Morales –Alamo, D
    University of Las Palmas, Spain.
    Efectos del ejercicio en la señalización de NF-kB durante la restricción calórica severa2017Conference paper (Refereed)
    Abstract [es]

    El sobrepeso y la obesidad, en crecimiento en todo el mundo, se asocian con una alta tasa de mortalidad e morbilidad[1,2]. La causa principal que conduce a éstas condiciones patológicas es un balance energético positivo sostenido a largo plazo, debido a la inactividad física y la ingesta calórica excesiva[3]. Por lo tanto, ejercicio físico y restricción calórica podrían ser dos estratégias eficaces para prevenir y contrastar el excesivo acumulo de grasa corporal que caracteriza estas patologías. Sin embargo, durante dietas muy bajas en calorías (<800 Kcal/día) se pierde no solo masa grasa sino también masa muscular, reportando efectos negativos para la salud[4]. En dichas condiciones,  el ejercicio físico permite preservar masa muscular de manera local y dosis-dependiente, mientras la ingestión de proteínas no ejerce particulares efectos protectivos sobre el tejido contráctil[5]. Los mecanismos moleculares implicados en la preservación de la masa muscular inducida por el ejercicio durante este tipo de dietas no han sido definidos claramente. NF-kB es un factor de transcripción cuya activación provoca atrofia muscular, y su bloqueo puede parcialmente limitar este fenomeno[6]. NF-kB se ha mostrado activado de manera aguda por el ejercicio y la restricción calorica, sin embargo no ha sido definida su respuesta a la restricción calórica en conjunción con el ejercicio prolongado de baja intensidad. Además, cuando los niveles basales de NF-kB son altos, el ejercicio no parece aumentar ulteriormente su señalización[7]. Por las razones presentadas, NF-kB podría desempeñar un rol en la preservación de masa magra inducida por el ejercicio durante  la restricción calórica.

    El objetivo del estudio es establecer la respuesta de NF-kB a la restricción calórica severa en conjunción con el ejercicio prolongado de baja intensidad. Las hipótesis fueron las siguientes: 1) la restricción calórica severa activaría la via de NF-kB y 2) dicha activación será atenuada por el ejercicio de manera local y dosis-dependiente.

    15 sujetos con sobrepeso y obesidad fueron sometidos a tres fases experimentales: fase 1, en la que la dieta y el nivel de actividad física de los participantes fue monitorizado durante una semana (PRE); fase 2, caracterizada por cuatro días de ejercicio prolongado y de restricción calórica severa (RCE); fase 3, caracterizada por tres días de ejercicio reducido y una dieta isoenergética (DC). Durante la fase 2, los sujetos ingeriron hidratos de carbono o proteínas (0.8 g/kg peso corporal/día; 320 kcal/día) y hicieron 45 minutos de pedaleo con un solo miembro superior (15% Ppeak) seguidos de 8 horas de caminata (4.5 km/h; 35 km/día). Las biopsias musculares fueron recogidas de ambos los deltoides y del vasto lateral en la fase 1 y después de la fase 2 y 3. Mediante Western blot, se determinó la expresión de NF-κB p105, NF-κB p50, la fosforilación de la Serina 32/36 de IκBα e IκBα total. La composición corporal se midió mediante DXA. Estadística: ANOVA para medidas repetidas.

    Durante los 4 días de restricción calórica severa el deficit energético fue de 5500 Kcal. Después de la fase 2 los sujetos perdieron menos masa magra en los miembros inferiores y en el brazo ejercitado respecto al brazo de control: 57% (P<0.05) y 29% (P=0.05), respectivamente. Tras la fase 2 y 3, el contenido de p105 y de p50 fue menor en los miembros inferiores respecto a los superiores: efecto extremidad P=0.003 y P=0.024 para p105 y p50, respectivamente. Tras la fase 3, la fosforilación de la Serina 32/36 de IkBα aumentó únicamente en las piernas, mientras la expresión total IkBα fue mayor solo en los miembros ejercitados (P<0.05).

    El ejercicio físico atenuó la activación de la señalización de NF-kB durante 4 días de restricción calórica severa, limitando el incremento de la expresión de p50 y p105, que resultó más baja después de la fase 2 y la fase 3 en los miembros inferiores respecto a los miembros superiores, posiblemente debido a la mayor cantidad de ejercicio a la que fueron sometidos. Además, la expresión total de IkBα fue más alta tras la fase 3 solo en los miembros ejercitados, indicando una posible inhibición de la vía de   NF-kB inducida por el ejercicio. Por lo tanto, dado la menor activación de la señalización de NF-kB en los miembros que perdieron menor masa muscular, los resultados sugieren que los efectos protectores del ejercicio físico sobre el tejido contráctil podrían ser mediados a una menor activación de la señalización de NF-kB.

    El ejercicio físico desempeña una función preservadora sobre la masa muscular durante la restricción calórica severa. La preservación de masa muscular es dosis-dependiente (a mayor volumen, mayor preservación) y está mediada, al menos parcialmente, por una menor activación de la señalización por NF-kB.

    1.Hill, J. O., H. R. Wyatt, et al. (2012). Circulation 126(1): 126-132.2.Di Angelantonio, E., N. Bhupathiraju Sh, et al. (2016). Lancet 388(10046): 776-786. 3.Chaston, T. B., J. B. Dixon, et al. (2007). Int J Obes (Lond) 31(5): 743-750. 4.Calbet, J. A., J. G. Ponce-Gonzalez, et al. (2017). Front Physiol (Accepted, In press).5.Cai, D., J. D. Frantz, et al. (2004). Cell 119(2): 285-298.6.Tantiwong, P., K. Shanmugasundaram, et al. (2010). Am J Physiol Endocrinol Metab 299(5): E794-801.7.NCD-RisC (2016). Lancet 387(10026): 1377-1396.

  • 17.
    Bakkman, Linda
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Sahlin, K
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Quantitative and qualitative adaptation of human skeletal muscle mitochondria to hypoxic compared to2007In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 190, no 3, p. 243-251Article in journal (Refereed)
    Abstract [en]

    AIM: To investigate if training during hypoxia (H) improves the adaptation of muscle oxidative function compared with normoxic (N) training performed at the same relative intensity. METHOD: Eight untrained volunteers performed one-legged cycle training during 4 weeks in a low-pressure chamber. One leg was trained under N conditions and the other leg under hypobaric hypoxia (526 mmHg) at the same relative intensity as during N (65% of maximal power output, W(max)). Muscle biopsies were taken from vastus lateralis before and after the training period. Muscle samples were analysed for the activities of oxidative enzymes [citrate synthase (CS) and cytochrome c oxidase (COX)] and mitochondrial respiratory function. RESULTS: W(max) increased with more than 30% over the training period during both N and H. CS activity increased significantly after training during N conditions (+20.8%, P < 0.05) but remained unchanged after H training (+4.5%, ns) with a significant difference between conditions (P < 0.05 H vs. N). COX activity was not significantly changed by training and was not different between exercise conditions [+14.6 (N) vs. -2.3% (H), ns]. Maximal ADP stimulated respiration (state 3) expressed per weight of muscle tended to increase after N (+31.2%, P < 0.08) but not after H training (+3.2%, ns). No changes were found in state four respiration, respiratory control index, P/O ratio, mitochondrial Ca(2+) resistance and apparent Km for oxygen. CONCLUSION: The training-induced increase in muscle oxidative function observed during N was abolished during H. Altitude training may thus be disadvantageous for adaptation of muscle oxidative function.

  • 18.
    Beaven, Martyn
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Willis, Sarah
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Cook, Christian
    School of Sport, Health and Exercise Sciences, Bangor University, Bangor, United Kingdom.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Physiological comparison of concentric and eccentric arm cycling in males and females2014In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 5, no 9, p. Art. no. e112079-Article in journal (Refereed)
    Abstract [en]

    Lower body eccentric exercise is well known to elicit high levels of muscular force with relatively low cardiovascular and metabolic strain. As a result, eccentric exercise has been successfully utilised as an adaptive stressor to improve lower body muscle function in populations ranging from the frail and debilitated, to highly-trained individuals. Here we investigate the metabolic, cardiorespiratory, and energy costs of upper body eccentric exercise in a healthy population. Seven men and seven women performed 4-min efforts of eccentric (ECC) or concentric (CON) arm cycling on a novel arm ergometer at workloads corresponding to 40, 60, and 80% of their peak workload as assessed in an incremental concentric trial. The heart rate, ventilation, cardiac output, respiratory exchange ratio, and blood lactate concentrations were all clearly greater in CON condition at all of the relative workloads (all p<0.003). Effect size calculations demonstrated that the magnitude of the differences in VO2 and work economy between the ECC and CON exercise ranged from very large to extremely large; however, in no case did mechanical efficiency (ηMECH) differ between the conditions (all p>0.05). In contrast, delta efficiency (ηΔ), as previously defined by Coyle and colleagues in 1992, demonstrated a sex difference (men>women; p<0.05). Sex differences were also apparent in arteriovenous oxygen difference and heart rate during CON. Here, we reinforce the high-force, low cost attributes of eccentric exercise which can be generalised to the muscles of the upper body. Upper body eccentric exercise is likely to form a useful adjunct in debilitative, rehabilitative, and adaptive clinical exercise programs; however, reports of a shift towards an oxidative phenotype should be taken into consideration by power athletes. We suggest delta efficiency as a sensitive measure of efficiency that allowed the identification of sex differences.

  • 19.
    Björklund, Glenn
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    A comparison between elite and well trained cross-country skiers in physiological response to variations in intensity during prolonged exercise2008In: 13th Annual Congress of the European College of Sports Science, Cologne: Sportools , 2008, p. 522-Conference paper (Refereed)
    Abstract [en]

     

    Introduction: Cross-country ski racing includes continual variations in intensity due to terrain and tactics {Mygind et al 1994; Norman et al 1989). Consequently, the recovery between periods with higher intensity might affect the outcome of the race. Both blood metabolites and respiratory variables are used for standard performance evaluations for endurance athletes, although there is a lack information if respiratory variables respond similar to blood lactate and acid/base values during prolonged variable exercise. Therefore, the aims with the present study were to 1) evaluate whether respiratory variables are associated with blood lactate and acid/base variables, 2) how/if these variables might predict physical performance and 3) whether a calculated heart rate-oxygen uptake (HR-VO2) relationship is valid during variable intensity exercise. Methods: 12 cross-country skiers classified as elite (E, n=6) and formerly well-trained (FWT, n=6) performed two roller ski tests. 1) An incremental test to establish maximal oxygen uptake (VO2max), maximum heart rate (HRmax) and lactate threshold (LT). Submaximal and maximal VO2 and HR during the incremental test were used for calculating the individual HR-VO2 linear relationship and 2) a 48-min long variable intensity protocol (VIP) at alternating exercise intensities, 90% (HI90) and 70% (MI70) of VO2max. Cardio-respiratory variables and venous blood samples were continuously collected throughout the VIP. Comparisons between E and FWT were performed using a two-tailed unpaired Student’s t-test and a ANCOVA analysis was used to determine which physiological variable best could prognosticate time to exhaustion (TTE). A simple linear regression was used to establish the relationship between HR and VO2. Results: Blood lactate concentrations [La] were higher and base excess [BE] lower for FWT from the first MI70 (P<0.05). FWT had augmented RER during all HI90 and an elevated VE/VO2 during the second and third HI90 in comparison to E (P<0.05). The expected HR were higher during the MI70 exercise intensities regardless of group affiliation (P<0.05). The blood [La] response predicted time to exhaustion earlier than respiratory variables (P<0.05). Discussion: Blood lactate and acid/base fluctuations were not reflected by RER and the ventilatory equivalents. Furthermore, blood lactate is to prefer, in comparison to ventilatory variables, to study performance related recovery processes during endurance exercise with variations in intensity. The expected HR-VO2 relationship was not valid during VIP.

     

  • 20.
    Björklund, Glenn
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Swedish Olymp Comm, Stockholm, Sweden.
    Stöggl, Thomas
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Salzburg Univ, Dept Sport Sci & Kinesiol, A-5020 Salzburg, Austria.
    The effects of prior high intensity double poling on subsequent diagonal stride skiing characteristics2015In: SpringerPlus, E-ISSN 2193-1801, Vol. 4, no 1Article in journal (Refereed)
    Abstract [en]

    Purpose: To investigate the influence of prior high intensity double poling (DP) on physiological and biomechanical responses during subsequent diagonal stride (DIA). Methods: Eight well-trained male cross-country skiers (age 22 ± 3 yr; VO2max 69 ± 3 ml · kg−1 · min−1) roller-skied on a treadmill sequentially for 3 min at 90% DIA VO2max (DIA1), 3 min at 90% DP VO2peak and 3 min at 90% DIA VO2max (DIA2). Cardio-respiratory responses were monitored continuously and gases and metabolites in blood from the a. femoralis, v. femoralis and v. subclavia determined. Pole and plantar forces and EMG from 6 lower- and upper-body muscles were measured. Results: VO2 decreased from DIA1 to DP and increased again to DIA2 (both P &lt; 0.05), with no difference between the DIA sessions. Blood lactate rose from DIA1 to DP to DIA2. O2 extraction was attenuated during DP (P &lt; 0.05), but was the same during DIA1 and DIA2. EMGRMS for arm muscles during poling phase, as well as peak pole force and cycle rate were higher, while leg muscle activity was lower during DP than both sessions of DIA (all P &lt; 0.05). The ratio of upper-/whole-body EMGRMS correlated negatively with O2 extraction in the arms during both sessions of DIA (P &lt; 0.05). Conclusions: In well-trained skiers skiing at high-intensity DP prior to DIA did not influence VO2, muscle activation or forces in the latter. At race intensity DP does not influence the distribution of work between upper- and lower-body during a subsequent bout of DIA. O2 extraction is coupled to technical skills during skiing.

  • 21.
    Björklund, Glenn
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Laaksonen, Marko
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Holmberg, H. -C
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Blood lactate recovery and respiratory responses during diagonal skiing of variable intensity2011In: European Journal of Sport Science, ISSN 1746-1391, E-ISSN 1536-7290, Vol. 11, no 5, p. 317-326Article in journal (Refereed)
    Abstract [en]

    The aims of the study were to investigate blood lactate recovery and respiratory variables during diagonal skiing of variable intensity in skiers at different performance levels. Twelve male cross-country skiers classified as elite (n=6; VO2max=73±3 ml. kg-1. min-1) or moderately trained (n=6; VO2max=61±5 ml. kg-1. min-1) performed a 48-min variable intensity protocol on a treadmill using the diagonal stride technique on roller skis, alternating between 3 min at 90% and 6 min at 70% of VO2max. None of the moderately trained skiers were able to complete the variable intensity protocol and there was a difference in time to exhaustion between the two groups (elite: 45.0±7.3 min; moderately trained: 31.4±10.4 min) (P&lt;0.05). The elite skiers had lower blood lactate concentrations and higher blood base excess concentrations at all 70% workloads than the moderately trained skiers (all P&lt;0.05). In contrast, VE/VO2 and VE/VCO2 at the 70% VO2max workloads decreased independently of group (P&lt;0.05). Partial correlations showed that VO2max was related to blood lactate at the first and second intervals at 70% of VO2max (r=-0.81 and r=-0.82; both P&lt;0.01) but not to VE/VO2, VE/VCO2 or the respiratory exchange ratio. Our results demonstrate that during diagonal skiing of variable intensity, (1) elite skiers have superior blood lactate recovery compared with moderately trained skiers, who did not show any lactate recovery at 70% of VO2max, suggesting it is an important characteristic for performance; and (2) the decreases in respiratory exchange ratio, VE/VO2, and VE/VCO2 do not differ between elite and moderately trained skiers.

  • 22.
    Björklund, Glenn
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Stöggl, Thomas
    Carlsson, Lars
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Dovrén, Louise
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    The relationship between oxygen extraction in the arms and legs to force and exercise intensity in diagonal skiing2009In: Proceedings of the 14th Annual Congress of European College of Sports Science / [ed] Loland, S., Bø, K., Fasting, K., Hallén, J., Ommundsen, Y., Roberts, G., Tsolakidis, E., Oslo: Gamlebyen Grafiske AS , 2009Conference paper (Refereed)
  • 23.
    Björklund, Glenn
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Stöggl, Thomas
    Department of Sport Science and Kinesiology, University of Salzburg, Austria.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Biomechanical influenced differences in O2 extraction in diagonal skiing: arm versus leg2010In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 42, no 10, p. 1899-1908Article in journal (Refereed)
    Abstract [en]

    Biomechanically Influenced Differences in O-2 Extraction in Diagonal Skiing: Arm versus Leg. Med. Sci. Sports Exerc., Vol. 42, No. 10, pp. 1899-1908, 2010. Purpose: This study aimed to determine whether the differences in oxygen extraction and lactate concentration in arms and legs during cross-country skiing are related to muscle activation or force production and how these differences are influenced by a reduction in exercise intensity. Methods: Nine well-trained male cross-country skiers (age = 22 +/- 3 yr, (V) over dotO(2max) = 5.3 +/- 0.3 L.min(-1) and 69 +/- 3 mL.kg(-1).min(-1)) performed diagonal skiing on a treadmill for 3 min at 90% followed by 6 min at 70% of (V) over dotO(2max). During the final minute of each workload, arterial, femoral, and subclavian venous blood was collected for determination of blood gases, pH, and lactate. EMG was recorded from six upper-and lower-body muscles, and leg and pole forces were measured. Cardiorespiratory variables were monitored continuously. Results: Oxygen extraction in the legs was higher than that in the arms at both 90% and 70% of (V) over dotO(2max) (92% +/- 3% vs 85% +/- 6%, P < 0.05 and 90% +/- 3% vs 78% +/- 8%, P < 0.001). This reduction with decreased workload was more pronounced in the arms (-9.8% +/- 7.7% vs -3.2% +/- 3.2%, P < 0.01). EMGRMS for the arms was higher, and pole ground contact time was greater than the corresponding values for the legs (both P < 0.01). At both intensities, the blood lactate concentration was higher in the subclavian than that in the femoral vein but was lowered more in the subclavian vein when intensity was reduced (all P < 0.001). Conclusions: The higher muscle activation (percentage of maximal voluntary isometric contraction) in the arms and the longer ground contact time of the poles than the legs contribute to the lower oxygen extraction and elevated blood lactate concentration in the arms in diagonal skiing. The better lactate recovery in the arms than that in the legs is aided by greater reductions in muscle activation and pole force when exercise intensity is reduced.

  • 24.
    Björklund, Glenn
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Stöggl, Thomas
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    NO EXCESS VO2 DURING WHOLE-BODY HIGH INTENSITY EXERCISE IN WELL-TRAINED CROSS-COUNTRY SKIERS2012In: Book of Abstracts of the 17th Annual Congress of the European College of Sport Science / [ed] Meeusen, R., Duchateau, J., Roelands, B., Klass, M., De Geus, B., Baudry, S., Tsolakidis, E., 2012, p. 54-54Conference paper (Refereed)
  • 25.
    Bolger, Claire
    et al.
    University of Aberdeen.
    Tufvesson, Ellen
    University of Lund.
    Stenfors, Nikolai
    University of Umeå.
    Devereux, Graham
    University of Aberdeen.
    Ayres, John
    University of Aberdeen.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Bjermer, Leif
    University of Lund.
    Sue-Chu, Malcolm
    Department of Lung Medicine, University Hospital, and Heart and Lung Institute Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
    Kippelen, Pascale
    University of Aberdeen.
    Urinary cc16 levels in winter versus summer sport athletes after eucapnic voluntary hyperpnoea2009Conference paper (Refereed)
    Abstract [en]

    Exercise induced bronchoconstriction (EIB) is highly prevalent in elite athletes, especially in those training in cold dry environments. Dehydration of the airways plays a key role in this process. EIB has recently been linked to airway epithelial injury in asthmatic individuals. The aim of the study is to determine whether a short period of hyperpnoea of dry air causes airway epithelial disruption in winter and/or summer sport athletes. We hypothesise that urinary level of the Clara cell protein (CC16) – an indirect marker of permeability/cellular integrity of the lung epithelial barrier – will be increased after a eucapnic voluntary hyperpnoea (EVH) test and that this increase will be larger in winter compared to summer athletes. Forty two female athletes – 28 summer athletes (age 31.1+/-1.7yr (SEM), training volume 9+/-1.1h/wk) and 14 winter athletes (age 21.4+/-0.8yr, training volume 12.0 ± 1.10h/wk) – took part in this study. They all performed an 8-min EVH test at a target ventilation rate of 30 times their baseline forced expiratory volume in one second (FEV1). After the challenge, FEV1 was measured in duplicate at 2, 5, 10, 15, 20, 30, 60 and 90min. A sustained decrease in FEV1 of at least 10% from baseline was considered positive. Urine samples were collected at baseline and at 30, 60 and 90min recovery. CC16 concentration was measured by enzyme immunoassay. Ten summer athletes had a positive test (max FEV1 fall = 19.6+/-2.4%), whilst eighteen of the summer athletes and all the winter athletes were negative (max FEV1 fall = 5.7+/-0.7% and 5.3+/-0.7%, respectively). CC16 increased significantly after the challenge in all three groups (P<0.01) with no difference between groups: delta CC16 (max post-EVH minus baseline) in summer EVH negative athletes was 0.241+/-0.1 ng/&#956;mol creatinine, 0.292+/-0.085 ng/&#956;mol creatinine in summer EVH positive athletes, and 0.123+/-0.047ng/&#956;mol creatinine in winter EVH negative athletes (P=0.415)In conclusion, a short period of hyperpnoea of dry air is associated with an increased rate of CC16 excretion in urine in both winter and summer athletes. This suggests that the integrity of the airway epithelium might be compromised by loss of airway surface lining fluid when athletes inhale dry air at high flow rates. This appears to occur irrespective of the degree of bronchoconstriction or regular training environment.

  • 26.
    Born, D. -P
    et al.
    Integrative and Experimental Exercise Science, Institute for Sport Sciences, University of Wuerzburg, Wuerzburg, Germany .
    Faiss, R.
    Swiss Federal Institute of Sport, Section for Elite Sport, Magglingen, Switzerland .
    Willis, Sara J.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Strahler, J.
    Clinical Biopsychology, University of Marburg, Marburg, Germany.
    Millet, G. P.
    ISSUL Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Sperlich, B.
    Integrative and Experimental Exercise Science, Institute for Sport Sciences, University of Wuerzburg, Wuerzburg, Germany .
    Circadian variation of salivary immunoglobin A, alpha-amylase activity and mood in response to repeated double-poling sprints in hypoxia2016In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 116, no 1, p. 1-10Article in journal (Refereed)
    Abstract [en]

    Purpose: To assess the circadian variations in salivary immunoglobin A (sIgA) and alpha-amylase activity (sAA), biomarkers of mucosal immune function, together with mood during 2 weeks of repeated sprint training in hypoxia (RSH) and normoxia (RSN). Methods: Over a 2-week period, 17 competitive cross-country skiers performed six training sessions, each consisting of four sets of five 10-s bouts of all-out double-poling under either normobaric hypoxia (FiO2: 13.8 %, 3000 m) or normoxia. The levels of sIgA and sAA activity and mood were determined five times during each of the first (T1) and sixth (T6) days of training, as well as during days preceding (baseline) and after the training intervention (follow-up). Results: With RSH, sIgA was higher on T6 than T1 (P = 0.049), and sAA was increased on days T1, T6, and during the follow-up (P &lt; 0.01). With RSN, sIgA remained unchanged and sAA was elevated on day T1 only (P = 0.04). Similarly, the RSH group demonstrated reduced mood on days T1, T6, and during the follow-up, while mood was lowered only on T1 with RSN (P &lt; 0.01). Conclusions: The circadian variation of sIgA and sAA activity, biomarkers of mucosal immune function, as well as mood were similar on the first day of training when repeated double-poling sprints were performed with or without hypoxia. Only with RSH did the levels of sIgA and sAA activity rise with time, becoming maximal after six training sessions, when mood was still lowered. Therefore, six sessions of RSH reduced mood, but did not impair mucosal immune function. © 2015, Springer-Verlag Berlin Heidelberg.

  • 27.
    Born, D. -P
    et al.
    Julius-Maximilians-Universität Würzburg, Institut für Sportwissenschaft, Integrative und Experimentelle Trainingswissenschaft, Judenbühlweg 11, 97082 Würzburg, Germany .
    Hoppe, M. W.
    Arbeitsbereich Bewegungswissenschaft, Sportwissenschaft, Bergische Universität Wuppertal, Germany .
    Lindner, N.
    Julius-Maximilians-Universität Würzburg, Institut für Sportwissenschaft, Integrative und Experimentelle Trainingswissenschaft, Judenbühlweg 11, 97082 Würzburg, Germany .
    Freiwald, J.
    Arbeitsbereich Bewegungswissenschaft, Sportwissenschaft, Bergische Universität Wuppertal, Germany .
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Sperlich, B.
    Julius-Maximilians-Universität Würzburg, Institut für Sportwissenschaft, Integrative und Experimentelle Trainingswissenschaft, Judenbühlweg 11, 97082 Würzburg, Germany .
    Hitze, Kälte und Höhenexposition im Fuβball: Adaptive Mechanismen und Verhaltensstrategien in variierenden Umweltbedingungen2014In: Sportverletzung, Sportschaden, ISSN 0932-0555, E-ISSN 1439-1236, Vol. 28, no 1, p. 17-23Article in journal (Refereed)
    Abstract [en]

    Football is played worldwide and players often have to cope with hot and cold temperatures as well as high altitude conditions. The upcoming and past world championships in Brazil, Qatar and South Africa illustrate the necessity for behavioural strategies and adaptation to extreme environmental conditions. When playing football in the heat or cold, special clothing, hydration and nutritional and acclimatisation strategies are vital for high-level performance. When playing at high altitude, the reduced oxygen partial pressure impairs endurance performance and alters the technical and tactical requirements. Special high-altitude adaptation and preparation strategies are essential for football teams based at sea-level in order to perform well and compete successfully. Therefore, the aim of the underlying review is: 1) to highlight the difficulties and needs of football teams competing in extreme environmental conditions, 2) to summarise the thermoregulatory, physiological, neuronal and psychological mechanism, and 3) to provide recommendations for coping with extreme environmental conditions in order to perform at a high level when playing football in the heat, cold and at high altitude.

  • 28.
    Born, Dennis
    et al.
    Dept of Sport Science, University of Wuppertal, Wuppertal, Germany.
    Sperlich, Billy
    Dept of Sport Science, University of Wuppertal, Wuppertal, Germany.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Bringing light into the dark: effects of compression clothing on performance and recovery2013In: International Journal of Sports Physiology and Performance, ISSN 1555-0265, E-ISSN 1555-0273, Vol. 8, no 1, p. 4-18Article, review/survey (Refereed)
    Abstract [en]

    To assess original research addressing the effect of the application of compression clothing on sport performance and recovery after exercise, a computer-based literature research was performed in July 2011 using the electronic databases PubMed, MEDLINE, SPORTDiscus, and Web of Science. Studies examining the effect of compression clothing on endurance, strength and power, motor control, and physiological, psychological, and biomechanical parameters during or after exercise were included, and means and measures of variability of the outcome measures were recorded to estimate the effect size (Hedges g) and associated 95% confidence intervals for comparisons of experimental (compression) and control trials (noncompression). The characteristics of the compression clothing, participants, and study design were also extracted. The original research from peer-reviewed journals was examined using the Physiotherapy Evidence Database (PEDro) Scale. Results indicated small effect sizes for the application of compression clothing during exercise for shortduration sprints (10-60 m), vertical-jump height, extending time to exhaustion (such as running at VO2maxor during incremental tests), and time-trial performance (3-60 min). When compression clothing was applied for recovery purposes after exercise, small to moderate effect sizes were observed in recovery of maximal strength and power, especially vertical-jump exercise; reductions in muscle swelling and perceived muscle pain; blood lactate removal; and increases in body temperature. These results suggest that the application of compression clothing may assist athletic performance and recovery in given situations with consideration of the effects magnitude and practical relevance.

  • 29.
    Born, Dennis
    et al.
    Dept. of Sport Science, University of Wuppertal, Wuppertal, Germany .
    Zinner, Christoph
    Inst. of Training Science and Sport Informatics, German Sport University Cologne, Cologne, Germany .
    Herlitz, B
    Dept. of Sport Science, University of Wuppertal, Wuppertal, Germany .
    Richter, K
    Dept. of Sport Science, University of Wuppertal, Wuppertal, Germany .
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Sperlich, Billy
    Dept. of Sport Science, University of Wuppertal, Wuppertal, Germany .
    Muscle oxygenation asymmetry in ice speed skaters is not compensated by compression2014In: International Journal of Sports Physiology and Performance, ISSN 1555-0265, E-ISSN 1555-0273, Vol. 9, no 1, p. 58-67Article in journal (Refereed)
    Abstract [en]

    PURPOSE:

    The present investigation assessed tissue oxygenation and local blood volume in both vastus lateralis muscles during 3000 m race simulations in elite speed skaters on ice and the effects of leg compression on physiological, perceptual and performance measures.

    METHODS:

    Ten (6 female) elite ice speed skaters completed two on-ice trials with and without leg compression. Tissue oxygenation and local blood volume in both vastus lateralis muscles was assessed by applying near-infrared spectroscopy (NIRS). Continuous measures of oxygen uptake, ventilation, heart rate and velocity were conducted throughout the race simulations as well as blood lactate concentration and ratings of perceived exertion before and after the trials. In addition, lap times were assessed.

    RESULTS:

    The investigation of tissue oxygenation in both vastus lateralis muscles revealed an asymmetry (P<0.00; effect size=1.81) throughout the 3000 m race simulation. The application of leg compression did not affect oxygenation asymmetry (smallest P=0.99; largest effect size=0.31) or local blood volume (P=0.33; 0.95). Lap times (P=0.88; 0.43), velocity (P=0.24; 0.84), oxygen uptake (P=0.79; 0.10), ventilation (P=0.11; 0.59), heart rate (P=0.21; 0.89), blood lactate concentration (P=0.82; 0.59) and ratings of perceived exertion (P=0.19; 1.01) were also unaffected by the different types of clothing.

    CONCLUSION:

    Elite ice speed skaters show an asymmetry in tissue oxygenation of both vastus lateralis muscles during 3000 m events remaining during the long gliding phases along the straight sections of the track. Based on our data, we conclude no performance enhancing benefits from wearing leg compression under a normal racing suit.

  • 30.
    Born, DP
    et al.
    Department of Sport Science, University of Würzburg.
    Faiss, R
    ISSUL-Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Switzerland.
    Willis, Sarah
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Strahler, J
    University of Marburg, Clinical Biopsychology, Marburg, Germany.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Millet, GP
    ISSUL-Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Switzerland.
    Sperlich, Billy
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Repeated Sprint Training By Elite Cross-Country Skiers Under Hypoxic Conditions Does Not Influence Their Mucosal Immune Function To A Greater Extent Than Identical Normoxic Training2014In: Proceedings of the 19th Annual Congress of the ECSS, 2014, p. 3-Conference paper (Refereed)
  • 31. Born, DP
    et al.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Goernert, F
    Sperlich, Billy
    A novel compression garment with adhesive silicone stripes improves repeated sprint performance: a multi-experimental approach on the underlying mechanisms.2014In: BMC Sports Science, Medicine and Rehabilitation, ISSN 2052-1847, Vol. 6, no 21Article in journal (Refereed)
    Abstract [en]

    BACKGROUND:

    Repeated sprint performance is determined by explosive production of power, as well as rapid recovery between successive sprints, and there is evidence that compression garments and sports taping can improve both of these factors.

    METHODS:

    In each of two sub-studies, female athletes performed two sets of 30 30-m sprints (one sprint per minute), one set wearing compression garment with adhesive silicone stripes (CGSS) intended to mimic taping and the other with normal clothing, in randomized order. Sub-study 1 (n = 12) focused on cardio-respiratory, metabolic, hemodynamic and perceptual responses, while neuronal and biomechanical parameters were examined in sub-study 2 (n = 12).

    RESULTS:

    In both sub-studies the CGSS improved repeated sprint performance during the final 10 sprints (best P < 0.01, d = 0.61). None of the cardio-respiratory or metabolic variables monitored were altered by wearing this garment (best P = 0.06, d = 0.71). Also during the final 10 sprints, rating of perceived exertion by the upper leg muscles was reduced (P = 0.01, d = 1.1), step length increased (P = 0.01, d = 0.91) and activation of the m. rectus femoris elevated (P = 0.01, d = 1.24), while the hip flexion angle was lowered throughout the protocol (best P < 0.01, d = 2.28) and step frequency (best P = 0.34, d = 0.2) remained unaltered.

    CONCLUSION:

    Although the physiological parameters monitored were unchanged, the CGSS appears to improve performance during 30 30-m repeated sprints by reducing perceived exertion and altering running technique.

  • 32. Brink-Elfegoun, T.
    et al.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Nordlund Ekblom, M.
    Ekblom, B.
    Neuromuscular and circulatory adaptation during combined arm and leg exercise with different maximal work loads2007In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 101, no 5, p. 603-611Article in journal (Refereed)
    Abstract [en]

    Cardiopulmonary kinetics and electromyographic activity (EMG) during exhausting exercise were measured in 8 males performing three maximal combined arm + leg exercises (cA+L). These exercises were performed at different rates of work (mean ± SD; 373 ± 48, 429 ± 55 and 521 ± 102 W) leading to different average exercise work times in all tests and subjects. reached a plateau versus work rate in every maximal cA+L exercise (range 6 min 33 s to 3 min 13 s). The three different exercise protocols gave a maximal oxygen consumption of 4.67 ± 0.57, 4.58 ± 0.52 and 4.66 ± 0.53 l min−1 (P = 0.081), and a maximal heart rate (HRmax) of 190 ± 6, 189 ± 4 and 189 ± 6 beats min−1 (P = 0.673), respectively. Root mean square EMG (EMGRMS) of the vastus lateralis and the triceps brachii muscles increased with increasing rate of work and time in all three cA+L protocols. The study demonstrates that despite different maximal rates of work, leading to different times to exhaustion, the circulatory adaptation to maximal exercise was almost identical in all three protocols that led to a plateau. The EMGRMS data showed increased muscle recruitment with increasing work rate, even though the HRmax and was the same in all three cA+L protocols. In conclusion, these findings do not support the theory of the existence of a central governor (CG) that regulates circulation and neuronal output of skeletal muscles during maximal exercise. Thibault Brink-Elfegoun and Hans-Christer Holmberg contributed equally to this article.

  • 33. Bucher, S
    et al.
    Supej, M
    Sandbakk, Ø
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    DOWNHILL TURN TECHNIQUES AND PERFORMANCE IN CROSS-COUNTRY SKIING: ASSOCIATIONS WITH MECHANICALAND PHYSICAL PARAMETERS2012In: Book of Abstracts of the 17th Annual Congress of the European College of Sport Science in Bruges, Belgium from 4-7 July 2012 / [ed] Meeusen, R., Duchateau, J., Roelands, B., Klass, M., De Geus, B., Baudry, S., Tsolakidis, E., 2012, p. 241-241Conference paper (Refereed)
  • 34. Bucher Sandbakk, Silvana
    et al.
    Supej, Matej
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Department of Biomechanics, Faculty of Sport, University of Ljubljana, Ljubljana, Slovenia.
    Sandbakk, Øyvind
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Department of Human Movement Science, Norwegian University of Science and Technology, Trondheim, Norway.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Downhill turn techniques and associated physical characteristics in cross-country skiers2014In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 24, no 4, p. 708-716Article in journal (Refereed)
    Abstract [en]

    Three dominant techniques are used for downhill turning in cross-country skiing. In this study, kinematic, kinetic, and temporal characteristics of these techniques are described and related to skier strength and power. Twelve elite female cross-country skiers performed six consecutive turns of standardized geometry while being monitored by a Global Navigation Satellite System. Overall time was used as an indicator of performance. Skiing and turning parameters were determined from skier trajectories; the proportional use of each technique was determined from video analysis. Leg strength and power were determined by isometric squats and countermovement jumps on a force plate. Snow plowing, parallel skidding, and step turning were utilized for all turns. Faster skiers employed less snow plowing and more step turning, more rapid deceleration and earlier initiation of step turning at higher speed (r = 0.80–0.93; all P < 0.01). Better performance was significantly correlated to higher mean speed and shorter trajectory (r

    = 0.99/0.65; both P < 0.05) and to countermovement jump characteristics of peak force, time to peak force, and rate of force development (r  = -0.71/0.78/-0.83; all P < 0.05). In conclusion, faster skiers used step turning to a greater extent and exhibited higher maximal leg power, which enabled them to combine high speeds with shorter trajectories during turns.

  • 35. Bucher, Silvana
    et al.
    Supej, Matej
    Sandbakk, Øyvind
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    MECHANICAL PARAMETERS AS PREDICTORS OF DOWNHILL TURN PERFORMANCE IN CROSS-COUNTRY SKIING2012In: / [ed] Anni Hakkarainen, Stefan Lindinger and Vesa Linnamo, 2012, p. 64-64Conference paper (Refereed)
  • 36.
    Calbet, J. A. L.
    et al.
    Univ Las Palmas Gran Canaria, Dept Phys Educ, Las Palmas Gran Canaria 35017, Canary Islands, Spain.
    Ponce-Gonzalez, J. G.
    Univ Las Palmas Gran Canaria, Dept Phys Educ, Las Palmas Gran Canaria 35017, Canary Islands, Spain.
    Perez-Suarez, I.
    Univ Las Palmas Gran Canaria, Dept Phys Educ, Las Palmas Gran Canaria 35017, Canary Islands, Spain.
    de la Calle Herrero, J.
    Univ Las Palmas Gran Canaria, Dept Phys Educ, Las Palmas Gran Canaria 35017, Canary Islands, Spain.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    A time-efficient reduction of fat mass in 4 days with exercise and caloric restriction2015In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 25, no 2, p. 223-233Article in journal (Refereed)
    Abstract [en]

    To determine whether a fast reduction in fat mass can be achieved in 4 days by combining caloric restriction (CR: 3.2kcal/kg body weight per day) with exercise (8-h walking+45-min arm cranking per day) to induce an energy deficit of approximate to 5000kcal/day, 15 overweight men underwent five experimental phases: pretest, exercise+CR for 4 days (WCR), control diet+reduced exercise for 3 days (DIET), and follow-up 4 weeks (POST1) and 1 year later (POST2). During WCR, the diet consisted solely of whey protein (n=8) or sucrose (n=7) (0.8g/kg body weight per day). After WCR, DIET, POST1, and POST2, fat mass was reduced by a mean of 2.1, 2.8, 3.8, and 1.9kg (P<0.05), with two thirds of this loss from the trunk; and lean mass by 2.8, 1.0, 0.5, and 0.4kg, respectively. After WCR, serum glucose, insulin, homeostatic model assessment, total and low-density lipoprotein cholesterol and triglycerides were reduced, and free fatty acid and cortisol increased. Serum leptin was reduced by 64%, 50%, and 33% following WCR, DIET, and POST1, respectively (P<0.05). The effects were similar in both groups. In conclusion, a clinically relevant reduction in fat mass can be achieved in overweight men in just 4 days by combining prolonged exercise with CR.

  • 37. Calbet, J
    et al.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Rosdahl,
    van Hall,
    Jensen-Urstad,
    Saltin, Bengt
    Why do the arms extract less oxygen than the legs during exercise?2005In: American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, ISSN 0363-6119, Vol. 289, p. 1448-1458Article in journal (Refereed)
    Abstract [en]

    To determine whether conditions for O2 utilization and O2 off-loading from the hemoglobin are different in exercising arms and legs, six cross-country skiers participated in this study. Femoral and subclavian vein blood flow and gases were determined during skiing on a treadmill at 76% maximal O2 uptake (O2 max) and at O2 max with different techniques: diagonal stride (combined arm and leg exercise), double poling (predominantly arm exercise), and leg skiing (predominantly leg exercise). The percentage of O2 extraction was always higher for the legs than for the arms. At maximal exercise (diagonal stride), the corresponding mean values were 93 and 85% (n = 3; P < 0.05). During exercise, mean arm O2 extraction correlated with the PO2 value that causes hemoglobin to be 50% saturated (P50: r = 0.93, P < 0.05), but for a given value of P50, O2 extraction was always higher in the legs than in the arms. Mean capillary muscle O2 conductance of the arm during double poling was 14.5 (SD 2.6) ml·min–1·mmHg–1, and mean capillary PO2 was 47.7 (SD 2.6) mmHg. Corresponding values for the legs during maximal exercise were 48.3 (SD 13.0) ml·min–1·mmHg–1 and 33.8 (SD 2.6) mmHg, respectively. Because conditions for O2 off-loading from the hemoglobin are similar in leg and arm muscles, the observed differences in maximal arm and leg O2 extraction should be attributed to other factors, such as a higher heterogeneity in blood flow distribution, shorter mean transit time, smaller diffusing area, and larger diffusing distance, in arms than in legs. diffusing capacity; fatigue; oxygen extraction; performance; training

  • 38. Calbet, J
    et al.
    Jensen-Urstad, M
    van Hall, G
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Rosdahl, H
    Saltin, Bengt
    Maximal vascular conductances during whole body upright exercise in humans2004In: The Journal of Physiology, ISSN 0022-3751, Vol. 558, no 1, p. 319-331Article in journal (Refereed)
    Abstract [en]

    That muscular blood flow may reach 2.5 l kg�1 min�1 in the quadriceps muscle has led to the suggestion that muscular vascular conductance must be restrained during whole body exercise to avoid hypotension. The main aim of this study was to determine the maximal arm and leg muscle vascular conductances (VC) during leg and arm exercise, to find out if the maximal muscular vasodilatory response is restrained during maximal combined arm and leg exercise. If during maximal exercise arms and legs had been vasodilated to the observed maximal levels then mean arterial pressure would have dropped at least to 75�77 mmHg in our experimental conditions. It is concluded that skeletal muscle vascular conductance is restrained during whole body exercise in the upright position to avoid hypotension. AVKORTAT ABSTRACT

  • 39.
    Calbet, Jose A. L.
    et al.
    Univ Las Palmas Gran Canaria, Dept Phys Educ, Las Palmas Gran Canaria, Spain; IUIBS, Res Inst Biomed & Hlth Sci, Las Palmas Gran Canaria, Spain.
    Ponce-Gonzalez, Jesus G.
    Univ Las Palmas Gran Canaria, Dept Phys Educ, Las Palmas Gran Canaria, Spain.
    de la Calle-Herrero, Jaime
    Univ Las Palmas Gran Canaria, Dept Phys Educ, Las Palmas Gran Canaria, Spain.
    Perez-Suarez, Ismael
    Univ Las Palmas Gran Canaria, Dept Phys Educ, Las Palmas Gran Canaria, Spain; IUIBS, Res Inst Biomed & Hlth Sci, Las Palmas Gran Canaria, Spain..
    Martin-Rincon, Marcos
    Univ Las Palmas Gran Canaria, Dept Phys Educ, Las Palmas Gran Canaria, Spain; IUIBS, Res Inst Biomed & Hlth Sci, Las Palmas Gran Canaria, Spain.
    Santana, Alfredo
    Univ Las Palmas Gran Canaria, Dept Phys Educ, Las Palmas Gran Canaria, Spain; IUIBS, Res Inst Biomed & Hlth Sci, Las Palmas Gran Canaria, Spain.
    Morales-Alamo, David
    Univ Las Palmas Gran Canaria, Dept Phys Educ, Las Palmas Gran Canaria, Spain; IUIBS, Res Inst Biomed & Hlth Sci, Las Palmas Gran Canaria, Spain.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Exercise Preserves Lean Mass and Performance during Severe Energy Deficit: The Role of Exercise Volume and Dietary Protein Content2017In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 8, article id 483Article in journal (Refereed)
    Abstract [en]

    The loss of fat-free mass (FFM) caused by very-low-calorie diets (VLCD) can be attenuated by exercise. The aim of this study was to determine the role played by exercise and dietary protein content in preserving the lean mass and performance of exercised and non-exercised muscles, during a short period of extreme energy deficit (similar to 23 MJ deficit/day). Fifteen overweight men underwent three consecutive experimental phases: baseline assessment (PRE), followed by 4 days of caloric restriction and exercise (CRE) and then 3 days on a control diet combined with reduced exercise (CD). During CRE, the participants ingested a VLCD and performed 45 min of one-arm cranking followed by 8 h walking each day. The VLCD consisted of 0.8 g/kg body weight/day of either whey protein (PRO, n = 8) or sucrose (SU, n = 7). FFM was reduced after CRE (P < 0.001), with the legs and the exercised arm losing proportionally less FFM than the control arm [57% (P < 0.05) and 29% (P = 0.05), respectively]. Performance during leg pedaling, as reflected by the peak oxygen uptake and power output (Wpeak), was reduced after CRE by 15 and 12%, respectively (P < 0.05), and recovered only partially after CD. The deterioration of cycling performance was more pronounced in the whey protein than sucrose group (P < 0.05). Wpeak during arm cranking was unchanged in the control arm, but improved in the contralateral arm by arm cranking. There was a linear relationship between the reduction in whole-body FFM between PRE and CRE and the changes in the cortisol/free testosterone ratio (C/FT), serum isoleucine, leucine, tryptophan, valine, BCAA, and EAA (r = -0.54 to -0.71, respectively, P < 0.05). C/FT tended to be higher in the PRO than the SU group following CRE (P = 0.06). In conclusion, concomitant low-intensity exercise such as walking or arm cranking even during an extreme energy deficit results in remarkable preservation of lean mass. The intake of proteins alone may be associated with greater cortisol/free testosterone ratio and is not better than the ingestion of only carbohydrates for preserving FFM and muscle performance in interventions of short duration.

  • 40.
    Cardinale, Daniele A.
    et al.
    Swedish Sch Sport & Hlth Sci, Stockholm.
    Larsen, Filip J.
    Swedish Sch Sport & Hlth Sci, Stockholm.
    Schiffer, Tomas A.
    Karolinska Inst, Stockholm.
    Morales-Alamo, David
    Univ Las Palmas Gran Canaria, Las Palmas Gran Canaria, Spain; Res Inst Biomed & Hlth Sci IUIBS, Las Palmas De Gran Canad, Gran Canaria, Spain.
    Ekblom, Bjorn
    Swedish Sch Sport & Hlth Sci, Stockholm.
    Calbet, Jose A. L.
    Univ Las Palmas Gran Canaria, Las Palmas Gran Canaria, Spain; Res Inst Biomed & Hlth Sci IUIBS, Las Palmas De Gran Canad, Gran Canaria, Spain; Univ British Columbia, Vancouver, BC, Canada.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Univ British Columbia, Vancouver, BC, Canada.
    Boushel, Robert
    Univ British Columbia, Vancouver, BC, Canada.
    Superior Intrinsic Mitochondria Respiration in Women Than in Men2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, no AUG, article id 1133Article in journal (Refereed)
    Abstract [en]

    Sexual dimorphism is apparent in humans, however, to date no studies have investigated mitochondria! function focusing on intrinsic mitochondrial respiration (i.e., mitochondrial respiration for a given amount of mitochondrial protein) and mitochondrial oxygen affinity (p50(mito)) in relation to biological sex in human. A skeletal muscle biopsy was donated by nine active women, and ten men matched for maximal oxygen consumption (VO2max) and by nine endurance trained men. Intrinsic mitochondrial respiration, assessed in isolated mitochondria, was higher in women compared to men when activating complex I (Cl-p) and complex I+II(Cl+IIp) (p < 0.05), and was similar to trained men (Cl-p, p = 0.053; Cl+IIp, p = 0.066). Proton leak and p50(mito) to were higher in women compared to men independent of VO2max. In conclusion, significant novel differences in mitochondrial oxidative function, intrinsic mitochondrial respiration and p50(mito) to exist between women and men. These findings may represent an adaptation in the oxygen cascade in women to optimize muscle oxygen uptake to compensate for a lower oxygen delivery during exercise.

  • 41. Carlsson, Lars
    et al.
    Isaksson, Dag
    Östersunds sjukhus.
    Lind, Britta
    School of Technology and Health, Royal Institute of Technology (KTH), Huddinge, Stockholm, Sweden.
    Andersson, Erik
    Brodin, Lars-Åke
    School of Technology and Health, Royal Institute of Technology (KTH), Huddinge, Stockholm, Sweden.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Enhanced myocardial peak systolic capacity in elite endurace athletes during exercise2009In: Proceedings of the 14th Annual Congress of European College of Sports Science / [ed] Loland, S., Bø, K., Fasting, K., Hallén, J., Ommundsen, Y., Roberts, G., Tsolakidis, E., Oslo: Gamlebyen Grafiske AS , 2009Conference paper (Refereed)
  • 42.
    Carlsson, Lars
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Lind, Britta
    Royal Inst Technol KTH, Sch Technol & Hlth, Stockholm, Sweden .
    Laaksonen, Marko
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Berglund, Bo
    Karolinska Inst, Dept Internal Med, S-10401 Stockholm, Sweden.
    Brodin, Lars-Åke
    Royal Inst Technol KTH, Sch Technol & Hlth, Stockholm, Sweden .
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Enhanced systolic myocardial function in elite endurance athletes during combined arm-and-leg exercise2011In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 111, no 6, p. 905-913Article in journal (Refereed)
    Abstract [en]

    The aim here was to employ color tissue velocity imaging (TVI), to test the hypothesis that highly trained endurance athletes exhibit enhanced systolic function of the left ventricular (LV) myocardium both at rest and during combined arm-and-leg exercise in comparison with untrained subjects. For each of the ten elite male (EG) and ten matched control participants (CG), LV dimensions and systolic function were assessed at rest using echocardiography. Subsequently, these subjects exercised continuously on a combined arm-and-leg cycle ergometer for 3 min each at 50, 60, 70, 80, 90 and 100% of VO2max. Oxygen uptake, heart rate, systolic blood pressure (SBP) and peak contraction systolic velocities of the LV myocardium (PSV) were recorded in the end of each level. At rest, the trained and untrained groups differed with respect to LV dimensions, but not systolic function. At 60–100% VO2max, the EG group demonstrated both higher PSV and SBP. The observation that the EG athletes had higher PSV than CG during exercise at 60–100% VO2max, but not at rest or at 50% of VO2max, suggested an enhanced systolic capacity. This improvement is likely to be due to an enhanced inotropic contractility, which only becomes apparent during exercise.

  • 43.
    Cheng, Arthur J.
    et al.
    Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden .
    Place, Nicolas
    Institute of Movement Sciences and Sports Medicine, Medicine Faculty, Geneva University, Geneva, Switzerland .
    Bruton, Joseph D.
    Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden .
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Westerblad, Håkan
    Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden .
    Doublet discharge stimulation increases sarcoplasmic reticulum Ca2+ release and improves performance during fatiguing contractions in mouse muscle fibres2013In: Journal of Physiology, ISSN 0022-3751, E-ISSN 1469-7793, Vol. 591, no 15, p. 3739-3748Article in journal (Refereed)
    Abstract [en]

    Double discharges (doublets) of motor neurones at the onset of contractions increase both force and rate of force development during voluntary submaximal contractions. The purpose of this study was to examine the role of doublet discharges on force and myoplasmic free [Ca2+] ([Ca2+](i)) during repeated fatiguing contractions, using a stimulation protocol mimicking the in vivo activation pattern during running. Individual intact fibres from the flexor digitorum brevis muscle of mice were stimulated at 33 degrees C to undergo 150 constant-frequency (five pulses at 70 Hz) or doublet (an initial, extra pulse at 200 Hz) contractions at 300 ms intervals. In the unfatigued state, doublet stimulation resulted in a transient (approximate to 10 ms) approximate doubling of [Ca2+](i), which was accompanied by a greater force-time integral (approximate to 70%) and peak force (approximate to 40%) compared to constant frequency contractions. Moreover, doublets markedly increased force-time integral and peak force during the first 25 contractions of the fatiguing stimulation. In later stages of fatigue, addition of doublets increased force production but the increase in force production corresponded to only a minor portion of the fatigue-induced reduction in force. In conclusion, double discharges at the onset of contractions effectively increase force production, especially in early stages of fatigue. This beneficial effect occurs without additional force loss in later stages of fatigue, indicating that the additional energy cost induced by doublet discharges to skeletal muscle is limited.

  • 44.
    Cheng, Arthur J.
    et al.
    Karolinska Institutet.
    Willis, Sarah J.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Zinner, Christoph
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Chaillou, Thomas
    Karolinska Institutet; Örebro universitet.
    Ivarsson, Niklas
    Karolinska Institutet.
    Ørtenblad, Niels
    University of Southern Denmark, Odense, Denmark.
    Lanner, Johanna T.
    Karolinska Institutet.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Karolinska Institutet.
    Westerblad, Håkan
    Karolinska Institutet.
    Post-exercise recovery of contractile function and endurance in humans and mice is accelerated by heating and slowed by cooling skeletal muscle2017In: Journal of Physiology, ISSN 0022-3751, E-ISSN 1469-7793, Vol. 595, no 24, p. 7413-7426Article in journal (Refereed)
    Abstract [en]

    Key points: We investigated whether intramuscular temperature affects the acute recovery of exercise performance following fatigue-induced by endurance exercise. Mean power output was better preserved during an all-out arm-cycling exercise following a 2 h recovery period in which the upper arms were warmed to an intramuscular temperature of ˜ 38°C than when they were cooled to as low as 15°C, which suggested that recovery of exercise performance in humans is dependent on muscle temperature. Mechanisms underlying the temperature-dependent effect on recovery were studied in intact single mouse muscle fibres where we found that recovery of submaximal force and restoration of fatigue resistance was worsened by cooling (16-26°C) and improved by heating (36°C). Isolated whole mouse muscle experiments confirmed that cooling impaired muscle glycogen resynthesis. We conclude that skeletal muscle recovery from fatigue-induced by endurance exercise is impaired by cooling and improved by heating, due to changes in glycogen resynthesis rate.

    Manipulation of muscle temperature is believed to improve post-exercise recovery, with cooling being especially popular among athletes. However, it is unclear whether such temperature manipulations actually have positive effects. Accordingly, we studied the effect of muscle temperature on the acute recovery of force and fatigue resistance after endurance exercise. One hour of moderate-intensity arm cycling exercise in humans was followed by 2 h recovery in which the upper arms were either heated to 38°C, not treated (33°C), or cooled to ∼15°C. Fatigue resistance after the recovery period was assessed by performing 3 × 5 min sessions of all-out arm cycling at physiological temperature for all conditions (i.e. not heated or cooled). Power output during the all-out exercise was better maintained when muscles were heated during recovery, whereas cooling had the opposite effect. Mechanisms underlying the temperature-dependent effect on recovery were tested in mouse intact single muscle fibres, which were exposed to ∼12 min of glycogen-depleting fatiguing stimulation (350 ms tetani given at 10 s interval until force decreased to 30% of the starting force). Fibres were subsequently exposed to the same fatiguing stimulation protocol after 1-2 h of recovery at 16-36°C. Recovery of submaximal force (30 Hz), the tetanic myoplasmic free [Ca2+] (measured with the fluorescent indicator indo-1), and fatigue resistance were all impaired by cooling (16-26°C) and improved by heating (36°C). In addition, glycogen resynthesis was faster at 36°C than 26°C in whole flexor digitorum brevis muscles. We conclude that recovery from exhaustive endurance exercise is accelerated by raising and slowed by lowering muscle temperature.

  • 45.
    Danielsen, Jorgen
    et al.
    Norwegian Univ Sci & Technol, Dept Neurosci, Ctr Elite Sports Res, N-7489 Trondheim, Norway..
    Sandbakk, Oyvind
    Norwegian Univ Sci & Technol, Dept Neurosci, Ctr Elite Sports Res, N-7489 Trondheim, Norway..
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Ettema, Gertjan
    Norwegian Univ Sci & Technol, Dept Neurosci, Ctr Elite Sports Res, N-7489 Trondheim, Norway.
    Mechanical Energy and Propulsion in Ergometer Double Poling by Cross-country Skiers2015In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 47, no 12, p. 2586-2594Article in journal (Refereed)
    Abstract [en]

    Purpose This study aims to investigate fluctuations in total mechanical energy of the body (E-body) in relation to external ergometer work (W-erg) during the poling and recovery phases of simulated double-poling cross-country skiing. Methods Nine male cross-country skiers (mean SD age, 24 5 yr; mean +/- SD body mass, 81.7 +/- 6.5 kg) performed 4-min submaximal tests at low-intensity, moderate-intensity, and high-intensity levels and a 3-min all-out test on a ski ergometer. Motion capture analysis and load cell recordings were used to measure body kinematics and dynamics. From these, W-erg, E-body (sum of the translational, rotational, and gravitational potential energies of all segments), and their time differentials (power P) were calculated. P(tot)the rate of energy absorption or generation by muscles-tendonswas defined as the sum of P-body and P-erg. ResultsE(body) showed large fluctuations over the movement cycle, decreasing during poling and increasing during the recovery phase. The fluctuation in P-body was almost perfectly out of phase with P-erg. Some muscle-tendon energy absorption was observed at the onset of poling. For the rest of poling and throughout the recovery phase, muscles-tendons generated energy to do W-erg and to increase E-body. Approximately 50% of cycle P-tot occurred during recovery for all intensity levels. Conclusions In double poling, the extensive contribution of the lower extremities and trunk to whole-body muscle-tendon work during recovery facilitates a direct transfer of E-body to W-erg during the poling phase. This observation reveals that double poling involves a unique movement pattern different from most other forms of legged terrestrial locomotion, which are characterized primarily by inverted pendulum or spring-mass types of movement.

  • 46.
    de Bruijn, Robert
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Richardson, Matthew
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Haughey, Helena
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Björklund, Glenn
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hemoglobin levels in elite divers, elite skiers and untrained humans2004Conference paper (Other academic)
  • 47.
    Dueking, Peter
    et al.
    Univ Wurzburg, Inst Sport Sci, Dept Sports Sci, Integrat & Expt Training Sci, D-97070 Wurzburg, Germany.
    Hotho, Andreas
    Univ Wurzburg, Data Min & Informat Retrieval Grp, Comp Sci Artificial Intelligence & Appl Comp Sci, D-97070 Wurzburg, Germany.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. UiT Arctic Univ Norway, Sch Sport Sci, Tromso, Norway.
    Fuss, Franz Konstantin
    RMIT Univ, Sch Engn, Dept Mech & Automot Engn, Melbourne, Vic, Australia.
    Sperlich, Billy
    Univ Wurzburg, Inst Sport Sci, Dept Sports Sci, Integrat & Expt Training Sci, D-97070 Wurzburg, Germany.
    Comparison of Non-Invasive Individual Monitoring of the Training and Health of Athletes with Commercially Available Wearable Technologies2016In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 7, article id 71Article, review/survey (Refereed)
    Abstract [en]

    Athletes adapt their training daily to optimize performance, as well as avoid fatigue, overtraining and other undesirable effects on their health. To optimize training load, each athlete must take his/her own personal objective and subjective characteristics into consideration and an increasing number of wearable technologies (wearables) provide convenient monitoring of various parameters. Accordingly, it is important to help athletes decide which parameters are of primary interest and which wearables can monitor these parameters most effectively. Here, we discuss the wearable technologies available for non-invasive monitoring of various parameters concerning an athlete's training and health. On the basis of these considerations, we suggest directions for future development. Furthermore, we propose that a combination of several wearables is most effective for accessing all relevant parameters, disturbing the athlete as little as possible, and optimizing performance and promoting health.

  • 48.
    Düking, Peter
    et al.
    University of Würzburg, Würzburg, Germany.
    Achtzehn, Silvia
    German Sport University, Cologne, Germany.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. UiT The Arctic University of Norway, Tromso, Norway.
    Sperlich, Billy
    University of Würzburg, Würzburg, Germany.
    Integrated framework of load monitoring by a combination of smartphone applications, wearables and point-of-care testing provides feedback that allows individual responsive adjustments to activities of daily living2018In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 18, no 5, article id 1632Article in journal (Refereed)
    Abstract [en]

    Athletes schedule their training and recovery in periods, often utilizing a pre-defined strategy. To avoid underperformance and/or compromised health, the external load during training should take into account the individual’s physiological and perceptual responses. No single variable provides an adequate basis for planning, but continuous monitoring of a combination of several indicators of internal and external load during training, recovery and off-training as well may allow individual responsive adjustments of a training program in an effective manner. From a practical perspective, including that of coaches, monitoring of potential changes in health and performance should ideally be valid, reliable and sensitive, as well as time-efficient, easily applicable, non-fatiguing and as non-invasive as possible. Accordingly, smartphone applications, wearable sensors and point-of-care testing appear to offer a suitable monitoring framework allowing responsive adjustments to exercise prescription. Here, we outline 24-h monitoring of selected parameters by these technologies that (i) allows responsive adjustments of exercise programs, (ii) enhances performance and/or (iii) reduces the risk for overuse, injury and/or illness.

  • 49.
    Düking, Peter
    et al.
    Julius Maximilians Univ, Wurzburg, Germany.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Karolinska Inst; UiT Arctic Univ, Norway.
    Sperlich, Billy
    Julius Maximilians Univ, Wurzburg, Germany.
    Instant biofeedback provided by wearable sensor technology can help to optimize exercise and prevent injury and overuse2017In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 8, no APR, article id 167Article in journal (Refereed)
  • 50.
    Düking, Peter
    et al.
    University of Würzburg, Würzburg, Germany.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. UiT The Arctic University of Norway, Tromsø, Norway; University of British Columbia, Vancouver, BC, Canada.
    Sperlich, Billy
    University of Würzburg, Würzburg, Germany.
    The potential usefulness of virtual reality systems for athletes: A short SWOT analysis2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, no MAR, article id 128Article in journal (Refereed)
1234567 1 - 50 of 362
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