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  • 1.
    Andersson, Erik
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Govus, Andrew
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. La Trobe University, Melbourne, VIC, Australia.
    Shannon, Oliver Michael
    Newcastle University, Newcastle upon Tyne, United Kingdom.
    McGawley, Kerry
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Sex differences in performance and pacing strategies during sprint skiing2019In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 10, article id 295Article in journal (Refereed)
    Abstract [en]

    Purpose: This study aimed to compare performance and pacing strategies between elite male and female cross-country skiers during a sprint competition on snow using the skating technique.

    Methods: Twenty male and 14 female skiers completed an individual time-trial prolog (TT) and three head-to-head races (quarter, semi, and final) on the same 1,572-m course, which was divided into flat, uphill and downhill sections. Section-specific speeds, choice of sub-technique (i.e., gear), cycle characteristics, heart rate and post-race blood lactate concentration were monitored. Power output was estimated for the different sections during the TT, while metabolic demand was estimated for two uphill camera sections and the final 50-m flat camera section.

    Results: Average speed during the four races was ∼12.5% faster for males than females (P < 0.001), while speeds on the flat, uphill and downhill sections were ∼11, 18, and 9% faster for the males than females (all P< 0.001 for terrain, sex, and interaction). Differences in uphill TT speed between the sexes were associated with different sub-technique preferences, with males using a higher gear more frequently than females (P < 0.05). The estimated metabolic demand relative to maximal oxygen uptake (V&#x2D9;" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V˙V˙O2max) was similar for both sexes during the two uphill camera sections (∼129% of V&#x2D9;" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V˙V˙O2max) and for the final 50-m flat section (∼153% of V&#x2D9;" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V˙V˙O2max). Relative power output during the TT was 18% higher for males compared to females (P < 0.001) and was highly variable along the course for both sexes (coefficient of variation [CV] between sections 4–9 was 53%), while the same variation in heart rate was low (CV was ∼3%). The head-to-head races were ∼2.4% faster than the TT for both sexes and most race winners (61%) were positioned first already after 30 m of the race. No sex differences were observed during any of the races for heart rate or blood lactate concentration.

    Conclusion: The average sex difference in sprint skiing performance was ∼12.5%, with varying differences for terrain-specific speeds. Moreover, females skied relatively slower uphill (at a lower gear) and thereby elicited more variation in their speed profiles compared to the males.

  • 2.
    Andersson, Erik
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    McGawley, Kerry
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    A Comparison between Different Methods of Estimating Anaerobic Energy Production2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, no FEB, article id 82Article in journal (Refereed)
    Abstract [en]

    Purpose: The present study aimed to compare four methods of estimating anaerobic energy production during supramaximal exercise.

    Methods: Twenty-one junior cross-country skiers competing at a national and/or international level were tested on a treadmill during uphill (7°) diagonal-stride (DS) roller-skiing. After a 4-minute warm-up, a 4 × 4-min continuous submaximal protocol was performed followed by a 600-m time trial (TT). For the maximal accumulated O2 deficit (MAOD) method the V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2-speed regression relationship was used to estimate the V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2 demand during the TT, either including (4+Y, method 1) or excluding (4-Y, method 2) a fixed Y-intercept for baseline V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2. The gross efficiency (GE) method (method 3) involved calculating metabolic rate during the TT by dividing power output by submaximal GE, which was then converted to a V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2 demand. An alternative method based on submaximal energy cost (EC, method 4) was also used to estimate V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2 demand during the TT.

    Results: The GE/EC remained constant across the submaximal stages and the supramaximal TT was performed in 185 ± 24 s. The GE and EC methods produced identical V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2 demands and O2 deficits. The V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2 demand was ~3% lower for the 4+Y method compared with the 4-Y and GE/EC methods, with corresponding O2 deficits of 56 ± 10, 62 ± 10, and 63 ± 10 mL·kg−1, respectively (P < 0.05 for 4+Y vs. 4-Y and GE/EC). The mean differences between the estimated O2 deficits were −6 ± 5 mL·kg−1 (4+Y vs. 4-Y, P < 0.05), −7 ± 1 mL·kg−1 (4+Y vs. GE/EC, P < 0.05) and −1 ± 5 mL·kg−1 (4-Y vs. GE/EC), with respective typical errors of 5.3, 1.9, and 6.0%. The mean difference between the O2 deficit estimated with GE/EC based on the average of four submaximal stages compared with the last stage was 1 ± 2 mL·kg−1, with a typical error of 3.2%.

    Conclusions: These findings demonstrate a disagreement in the O2 deficits estimated using current methods. In addition, the findings suggest that a valid estimate of the O2 deficit may be possible using data from only one submaximal stage in combination with the GE/EC method.

  • 3.
    Björklund, Glenn
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. The Swedish Sports Confederation, Stockholm, Sweden.
    Swarén, Mikael
    Kungliga Tekniska Högskolan.
    Born, Dennis-Peter
    Swiss Federal Institute of Sport, Magglingen, Switzerland.
    Stöggl, Thomas
    University of Salzburg, Salzburg, Austria.
    Biomechanical Adaptations and Performance Indicators in Short Trail Running2019In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 10, article id 506Article in journal (Refereed)
    Abstract [en]

    Our aims were to measure anthropometric and oxygen uptake (V&#x2D9;" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; font-size: 20px; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; color: rgb(62, 61, 64); font-family: Georgia, "Times New Roman", Times, serif; position: relative; outline: 0px !important;">V˙V˙O2) variables in the laboratory, to measure kinetic and stride characteristics during a trail running time trial, and then analyse the data for correlations with trail running performance. Runners (13 men, 4 women: mean age: 29 ± 5 years; stature: 179.5 ± 0.8 cm; body mass: 69.1 ± 7.4 kg) performed laboratory tests to determine V&#x2D9;" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; font-size: 20px; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; color: rgb(62, 61, 64); font-family: Georgia, "Times New Roman", Times, serif; position: relative; outline: 0px !important;">V˙V˙O2 max, running economy (RE), and anthropometric characteristics. On a separate day they performed an outdoor trail running time trial (two 3.5 km laps, total climb: 486 m) while we collected kinetic and time data. Comparing lap 2 with lap 1 (19:40 ± 1:57 min vs. 21:08 ± 2:09 min, P < 0.001), runners lost most time on the uphill sections and least on technical downhills (-2.5 ± 9.1 s). Inter-individual performance varied most for the downhills (CV > 25%) and least on flat terrain (CV < 10%). Overall stride cycle and ground contact time (GCT) were shorter in downhill than uphill sections (0.64 ± 0.03 vs. 0.84 ± 0.09 s; 0.26 ± 0.03 vs. 0.46 ± 0.90 s, both P < 0.001). Force impulse was greatest on uphill (248 ± 46 vs. 175 ± 24 Ns, P < 0.001) and related to GCT (r = 0.904, P< 0.001). Peak force was greater during downhill than during uphill running (1106 ± 135 vs. 959 ± 104 N, P< 0.01). Performance was related to absolute and relative V&#x2D9;" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; font-size: 20px; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; color: rgb(62, 61, 64); font-family: Georgia, "Times New Roman", Times, serif; position: relative; outline: 0px !important;">V˙V˙O2 max (P < 0.01), vertical uphill treadmill speed (P < 0.001) and fat percent (P < 0.01). Running uphill involved the greatest impulse per step due to longer GCT while downhill running generated the highest peak forces. V&#x2D9;" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; font-size: 20px; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; color: rgb(62, 61, 64); font-family: Georgia, "Times New Roman", Times, serif; position: relative; outline: 0px !important;">V˙V˙O2 max, vertical running speed and fat percent are important predictors for trail running performance. Performance between runners varied the most on downhills throughout the course, while pacing resembled a reversed J pattern. Future studies should focus on longer competition distances to verify these findings and with application of measures of 3D kinematics.

  • 4.
    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.

  • 5.
    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.

  • 6.
    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.

  • 7.
    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)
  • 8.
    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)
  • 9.
    Fernández, Fran de Asís
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Universidad Autónoma de Madrid, Madrid, Spain.
    Rodríguez-Zamora, Lara
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Örebro University, Örebro.
    Schagatay, Erika
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Hook Breathing Facilitates SaO2 Recovery After Deep Dives in Freedivers With Slow Recovery2019In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 10, p. 1-8, article id 1076Article in journal (Refereed)
    Abstract [en]

    To facilitate recovery from hypoxia, many freedivers use a breathing method called “hook breathing” (HB) after diving, involving an interrupted exhale to build up intrapulmonary pressure. Some divers experience a delay in recovery of arterial oxygen saturation (SaO2) after diving, interpreted as symptoms of mild pulmonary edema, and facilitated recovery may be especially important in this group to avoid hypoxic “blackout.” We examined the influence of HB on recovery of SaO2 in freedivers with slow recovery (SR) and fast recovery (FR) of SaO2 after deep “free immersion” (FIM) apnea dives to 30 m depth. Twenty-two male freedivers, with a mean (SD) personal best in the discipline FIM of 57(26) m, performed two 30 m deep dives, one followed by HB and one using normal breathing (NB) during recovery, at different days and weighted order. SaO2 and heart rate (HR) were measured via pulse oximetry during recovery. The SR group (n = 5) had a faster SaO2 recovery using HB, while the FR group (n = 17) showed no difference between breathing techniques. At 105 s, the SR group reached a mean (SD) SaO2 of 95(5)% using HB, while using NB, their SaO2 was 87(5)% (p < 0.05), and 105–120 s after surfacing SaO2 was higher with HB (p < 0.05). In SR subjects, the average time needed to reach 95% SaO2 with HB was 60 s, while it was 120 s at NB (p < 0.05). HR was similar in the SR group, while it was initially elevated at HB in the FR group (p < 0.05). We conclude that HB efficiently increases SaO2 recovery in SR individuals, but not in the FR group. The proposed mechanism is that increased pulmonary pressure with HB will reverse any pulmonary edema and facilitate oxygen uptake in divers with delayed recovery.

  • 10.
    Gilgien, Matthias
    et al.
    Norwegian Sch Sport Sci, Oslo, Norway; Norwegian Ski Federat, Alpine Skiing, Oslo, Norway.
    Reid, Robert
    Norwegian Ski Federat, Alpine Skiing, Oslo, Norway.
    Raschner, Christian
    Univ Innsbruck, Olymp Training Ctr, Innsbruck, Austria.
    Supej, Matej
    Univ Ljubljana, Ljubljana, Slovenia.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. UiT Arctic Univ Norway, Tromsø, Norway; Univ British Columbia, Vancouver, BC, Canada.
    The Training of Olympic Alpine Ski Racers2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, article id 1772Article in journal (Refereed)
    Abstract [en]

    Alpine combined was the only alpine ski racing event at the first Winter Olympic Games in 1936, but since then, slalom, giant slalom, super-G, downhill, and team events have also become Olympic events. Substantial improvements in slope preparation, design of courses, equipment, and the skills of Olympic alpine skiers have all helped this sport attain its present significance. Improved snow preparation has resulted in harder surfaces and improved equipment allows a more direct interaction between the skier and snow. At the same time, courses have become more challenging, with technical disciplines requiring more pronounced patterns of loading - unloading, with greater ground reaction forces. Athletes have adapted their training to meet these new demands, but little is presently known about these adaptations. Here, we describe how Olympic athletes from four of the major alpine ski racing nations prepared for the Olympic Games in South Korea in 2018. This overview describes their typical exercise programs with respect to physical conditioning, ski training and periodization, based on interviews with the coaching staff. Alpine ski racing requires mastery of a broad spectrum of physical, technical, mental, and social skills. We describe how athletes and teams deal with the multifactorial nature of the training required. Special emphasis is placed on sport-specific aspects, such as the combination of stimuli that interfere with training, training with chronic injury, training at altitude and in cold regions, the efficiency and effectiveness of ski training and testing, logistic challenges and their effects on fatigue, including the stress of frequent traveling. Our overall goal was to present as complete a picture of the training undertaken by Olympic alpine skiers as possible and on the basis of these findings propose how training for alpine ski racing might be improved.

  • 11.
    Holmström, Pontus
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Mulder, Eric
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Lodin-Sundström, Angelica
    Mid Sweden University, Faculty of Human Sciences, Department of Nursing Sciences.
    Limbu, Prakash
    Nepalese Army Inst Hlth Sci, Kathmandu, Nepal.
    Schagatay, Erika
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    The Magnitude of Diving Bradycardia During Apnea at Low-Altitude Reveals Tolerance to High Altitude Hypoxia2019In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 10, p. 1-12, article id 1075Article in journal (Refereed)
    Abstract [en]

    Acute mountain sickness (AMS) is a potentially life-threatening illness that may develop during exposure to hypoxia at high altitude (HA). Susceptibility to AMS is highly individual, and the ability to predict it is limited. Apneic diving also induces hypoxia, and we aimed to investigate whether protective physiological responses, i.e., the cardiovascular diving response and spleen contraction, induced during apnea at low-altitude could predict individual susceptibility to AMS. Eighteen participants (eight females) performed three static apneas in air, the first at a fixed limit of 60 s (A1) and two of maximal duration (A2-A3), spaced by 2 min, while SaO(2), heart rate (HR) and spleen volume were measured continuously. Tests were conducted in Kathmandu (1470 m) before a 14 day trek to mount Everest Base Camp (5360 m). During the trek, participants reported AMS symptoms daily using the Lake Louise Questionnaire (LLQ). The apnea-induced HR-reduction (diving bradycardia) was negatively correlated with the accumulated LLQ score in A1 (r(s) = -0.628, p= 0.005) and A3 (r(s) = -0.488, p = 0.040) and positively correlated with SaO(2) at 4410 m (A1: r = 0.655, p = 0.003; A2: r = 0.471, p = 0.049; A3: r = 0.635, p = 0.005). Baseline spleen volume correlated negatively with LLQ score (r(s) = -0.479, p = 0.044), but no correlation was found between apnea-induced spleen volume reduction with LLQ score (r(s) = 0.350, p = 0.155). The association between the diving bradycardia and spleen size with AMS symptoms suggests links between physiological responses to HA and apnea. Measuring individual responses to apnea at sea-level could provide means to predict AMS susceptibility prior to ascent.

  • 12.
    Ihalainen, Johanna K.
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Univ Jyväskylä, Jyväskylä, Finland.
    Inglis, Alistair
    Univ Jyväskylä, Jyväskylä, Finland.
    Mäkinen, Tuomas
    LIKES Res Ctr Sport & Hlth Sci, Jyväskylä, Finland.
    Newton, Robert U.
    Edith Cowan Univ, Joondalup, WA, Australia.
    Kainulainen, Heikki
    Univ Jyväskylä, Jyväskylä, Finland.
    Kyröläinen, Heikki
    Univ Jyväskylä, Jyväskylä, Finland.
    Walker, Simon
    Univ Jyväskylä, Jyväskylä, Finland.
    Strength Training Improves Metabolic Health Markers in Older Individual Regardless of Training Frequency2019In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 10, no FEB, article id 32Article in journal (Refereed)
    Abstract [en]

    The main purpose of the present study was to investigate the effect of frequency, thereby increasing training volume, of resistance training on body composition, inflammation markers, lipid and glycemic profile in healthy older individuals (age range 65-75 year). Ninety-two healthy participants were randomly assigned to one of four groups; performing strength training one- (EX1), two- (EX2), or three- (EX3) times-per-week and a non-training control (CON) group. Whole-body strength training was performed using 2-5 sets and 4-12 repetitions per exercise and 7-9 exercises per session. All training groups attended supervised resistance training for 6 months. Body composition was measured by dual X-ray absorptiometry and fasting blood samples were taken pre- and post-training. There were significant main effects of time for total fat mass (F = 28.12, P < 0.001) and abdominal fat mass (F = 20.72, P < 0.001). Pre- to post-study, statistically significant reductions in fat mass (Delta = -1.3 +/- 1.4 kg, P < 0.001, n = 26) were observed in EX3. Pre- to post-study reductions in low density lipoprotein (LDL) concentration (Delta = -0.38 +/- 0.44 mmol.L-1 , P = 0.003, n = 19) were observed only in EX3, whereas a significant pre- to post-study increases in high density lipoprotein (HDL) concentration (0.14-0.19 mmol.L-1) were observed in all training groups. Most variables at baseline demonstrated a significant (negative) relationship when correlating baseline values with their change during the study including: Interleukin-6 (IL-6) (r = -0.583, P < 0.001), high-sensitivity c-reactive protein (hs-CRP) (r = -0.471, P < 0.001, and systolic blood pressure (r = -0.402, P = 0.003). The present study suggests that having more than two resistance training sessions in a week could be of benefit in the management of body composition and lipid profile. Nevertheless, interestingly, and importantly, those individuals with a higher baseline in systolic blood pressure, IL-6 and hs-CRP derived greatest benefit from the resistance training intervention, regardless of how many times-a-week they trained. Finally, the present study found no evidence that higher training frequency would induce greater benefit regarding inflammation markers or glycemic profile in healthy older adults.

  • 13.
    Karlsson, Øyvind
    et al.
    Department of Physical Performance, Norwegian School of Sport Sciences.
    Gilgien, Matthias
    Department of Physical Performance, Norwegian School of Sport Sciences.
    Nøstdahl Gløersen, Øyvind
    Department of Physical Performance, Norwegian School of Sport Sciences.
    Rud, Bjarne
    Department of Physical Performance, Norwegian School of Sport Sciences.
    Losnegard, Thomas
    Department of Physical Performance, Norwegian School of Sport Sciences.
    Exercise Intensity During Cross-Country Skiing Described by Oxygen Demands in Flat and Uphill Terrain2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, article id 846Article in journal (Refereed)
    Abstract [en]

    Purpose: In this study wearable global navigation satellite system units were used on athletes to investigate pacing patterns by describing exercise intensities in flat and uphill terrain during a simulated cross-country ski race.

    Methods: Eight well-trained male skiers (age: 23.0 ± 4.8 years, height: 183.8 ± 6.8 cm, weight: 77.1 ± 6.1 kg, VO2peak: 73 ± 5 mL⋅kg-1⋅min-1) completed a 13.5-km individual time trial outdoors and a standardized indoor treadmill protocol on roller skis. Positional data were recorded during the time trial using a differential global navigation satellite system to calculate external workloads in flat and uphill terrain. From treadmill tests, the individual relationships between oxygen consumption and external workload in flat (1°) and uphill (8°) terrain were determined, in addition to VO2peak and the maximal accumulated O2-deficit. To estimate the exercise intensity in the time trial, the O2-demand in two different flat and five different uphill sections was calculated by extrapolation of individual O2-consumption/workload ratios.

    Results: There was a significant interaction between section and average O2-demands, with higher O2-demands in the uphill sections (110–160% of VO2peak) than in the flat sections (≤100% of VO2peak) (p < 0.01). The maximal accumulated O2-deficit associated with uphill treadmill roller skiing was significantly higher compared to flat (6.2 ± 0.5 vs. 4.6 ± 0.5 L, p < 0.01), while no significant difference was found in VO2peak.

    Conclusion: Cross-country (XC) skiers repeatedly applied exercise intensities exceeding their maximal aerobic power. ΣO2-deficits were higher during uphill skiing compared to flat which has implications for the duration and magnitude of supramaximal work rates that can be applied in different types of terrain.

  • 14.
    Laaksonen, Marko
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Jonsson, Malin
    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. UiT The Arctic University of Norway, Tromsø, Norway; The University of British Columbia, Vancouver, BC, Canada.
    The Olympic biathlon – Recent advances and perspectives after Pyeongchang2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, no JUL, article id 796Article in journal (Refereed)
    Abstract [en]

    The biathlon, combining cross-country ski skating with rifle marksmanship, has been an Olympic event since the Winter Games in Squaw Valley, United States, in 1960. As a consequence of replacing the classical with the skating technique in the 1980s, as well as considerable improvements in equipment and preparation of ski tracks and more effective training, the average biathlon skiing speed has increased substantially. Moreover, the mass-start, pursuit, and sprint races have been introduced. Indeed, two of the four current individual Olympic biathlon competitions involve mass-starts, where tactics play a major role and the outcome is often decided during the last round of shooting or final sprint. Biathlon is a demanding endurance sport requiring extensive aerobic capacity. The wide range of speeds and slopes involved requires biathletes to alternate continuously between and adapt different skating sub-techniques duringraces, a technical complexity that places a premium on efficiency. Although the relative amounts of endurance training at different levels of intensity have remained essentially constant during recent decades, today’s biathletes perform more specific endurance training on roller skis on terrain similar to that used for competition, with more focus on the upper-body, systematic strength and power training and skiing at higher speeds. Success in the biathlon also requires accurate and rapid shooting while simultaneously recovering from high-intensity skiing. Many different factors, including body sway, triggering behavior, and even psychology, influence the shooting performance. Thus, the complexity of biathlon deserves a greater research focus on areas such as race tactics, skating techniques, or shooting process.

  • 15.
    Laaksonen, Marko
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Kyröläinen, Heikki
    University of Jyväskylä, Finland.
    Kemppainen, Jukka
    University of Turku, Finland.
    Knuuti, Juhani
    University of Turku, Finland.
    Kalliokoski, Kari
    University of Turku, Finland.
    Muscle free fatty-acid uptake associates to mechanical efficiency during exercise in humans2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, no AUG, article id 1171Article in journal (Refereed)
    Abstract [en]

    Intrinsic factors related to muscle metabolism may explain the differences in mechanical efficiency (ME) during exercise. Therefore, this study aimed to investigate the relationship between muscle metabolism and ME. Totally 17 healthy recreationally active male subjects were recruited and divided into efficient (EF; n=8) and inefficient (IE; n=9) groups, which were matched for age (mean±SD 24±2 vs. 23±2 yrs), BMI (23±1 vs. 23±2 kg m-2), physical acitivity levels (3.4±1.0 vs. 4.1±1.0 sessions/week), and V ̇O2peak (53±3 vs. 52±3 mL kg-1 min-1), respectively, but differed for ME at 45% of VO2peak intensity during submaximal bicycle ergometer test (EF 20.5±3.5 vs. IE 15.4±0.8 %, P < 0.001). Using Positron Emission Tomography, muscle blood flow (BF) and uptakes of oxygen (mVO2), fatty acids (FAU) and glucose (GU) were measured during dynamic submaximal knee-extension exercise. Workload-normalized BF (EF 35±14 vs. IE 34±11 mL 100g-1 min-1, P = 0.896), mVO2 (EF 4.1±1.2 vs. IE 3.9±1.2 mL 100g-1 min-1, P = 0.808), and GU (EF 3.1±1.8 vs. IE 2.6±2.3 μmol 100g-1 min-1, P = 0.641) as well as the delivery of oxygen, glucose, and fatty acids, as well as respiratory quotient were not different between the groups. However, FAU was significantly higher in EF than IE (3.1±1.7 vs. 1.7±0.6 μmol 100g-1 min-1, P < 0.047) and it also correlated with ME (r=0.56, P < 0.024) in the entire study group. EF group also demonstrated higher use of plasma fatty acids than IE, but no differences in use of plasma glucose and intramuscular energy sources were observed between the groups. These findings suggest that the effective use of plasma fatty acids is an important determinant of mechanical efficiency during exercise.

  • 16.
    Marsland, Finn
    et al.
    Univ Canberra, Canberra, ACT, Australia; Australian Inst Sport, Canberra, ACT, Australia.
    Anson, Judith
    Univ Canberra, Canberra, ACT, Australia.
    Waddington, Gordon
    Univ Canberra, Canberra, ACT, Australia.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. UiT Arctic Univ Norway, Sch Sport Sci, Tromso, Norway.
    Chapman, Dale W.
    Univ Canberra, Canberra, ACT, Australia; Australian Inst Sport, Canberra, ACT, Australia.
    Macro-Kinematic Differences Between Sprint and Distance Cross-Country Skiing Competitions Using the Classical Technique2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, no MAY, article id 570Article in journal (Refereed)
    Abstract [en]

    We compare the macro-kinematics of six elite female cross-country skiers competing in 1.1-km Sprint and 10.5-km Distance classical technique events on consecutive days under similar weather and track conditions. The relative use of double pole (DP), kick-double pole (KDP), diagonal stride (DS), tucking (Tuck) and turning (Turn) sub-techniques, plus each technique's respective velocities, cycle lengths and cycle rates were monitored using a single micro-sensor unit worn by each skier during the Sprint qualification, semi-final and finals, and multiple laps of the Distance race. Over a 1.0-km section of track common to both Sprint and Distance events, the mean race velocity, cyclical sub-technique velocities, and cycle rates were higher during the Sprint race, while Tuck and Turn velocities were similar. Velocities with KDP and DS on the common terrain were higher in the Sprint (KDP +12%, DS +23%) due to faster cycle rates (KDP +8%, DS +11 %) and longer cycle lengths (KDP +5%, DS +10%), while the DP velocity was higher (+8%) with faster cycle rate (+16%) despite a shorter cycle length (-9%). During the Sprint the percentage of total distance covered using DP was greater (+15%), with less use of Tuck (-19%). Across all events and rounds, DP was the most used sub-technique in terms of distance, followed by Tuck, DS, Turn and KDP. KDP was employed relatively little, and during the Sprint by only half the participants. Tuck was the fastest sub-technique followed by Turn, DP, KDP, and DS, These findings reveal differences in the macro-kinematic characteristics and strategies utilized during Sprint and Distance events, confirm the use of higher cycle rates in the Sprint, and increase our understanding of the performance demands of cross-country skiing competition.

  • 17.
    McGawley, Kerry
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    The reliability and validity of a four-minute running time-trial in assessing VO2max and performance2017In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 8, no MAY, p. 1-9, article id 270Article in journal (Refereed)
    Abstract [en]

    Introduction: Traditional graded-exercise tests to volitional exhaustion (GXTs) are limited by the need to establish starting workloads, stage durations, and step increments. Short-duration time-trials (TTs) may be easier to implement and more ecologically valid in terms of real-world athletic events. The purpose of the current study was to assess the reliability and validity of maximal oxygen uptake (VO2max) and performance measured during a traditional GXT (STEP) and a four-minute running time-trial (RunTT). Methods: Ten recreational runners (age: 32 ± 7 years; body mass: 69 ± 10 kg) completed five STEP tests with a verification phase (VER) and five self-paced RunTTs on a treadmill. The order of the STEP/VER and RunTT trials was alternated and counter-balanced. Performance was measured as time to exhaustion (TTE) for STEP and VER and distance covered for RunTT. Results: The coefficient of variation (CV) for VO2max was similar between STEP, VER, and RunTT (1.9 ± 1.0, 2.2 ± 1.1, and 1.8 ± 0.8%, respectively), but varied for performance between the three types of test (4.5 ± 1.9, 9.7 ± 3.5, and 1.8 ± 0.7% for STEP, VER, and RunTT, respectively). Bland-Altman limits of agreement (bias ± 95%) showed VO2max to be 1.6 ± 3.6 mL·kg-1·min-1 higher for STEP vs. RunTT. Peak HR was also significantly higher during STEP compared with RunTT (P = 0.019). Conclusion: A four-minute running time-trial appears to provide more reliable performance data in comparison to an incremental test to exhaustion, but may underestimate VO2max.

  • 18.
    McGawley, Kerry
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Juudas, Elisabeth
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Kazior, Zuzanna
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Åstrand Laboratory, Swedish School of Sport and Health Sciences, Stockholm, Sweden.
    Ström, Kristoffer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Lunds Universitet.
    Blomstrand, Eva
    Åstrand Laboratory, Swedish School of Sport and Health Sciences, Stockholm, Sweden.
    Hansson, Ola
    Lunds Universitet.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    No additional benefits of block-over evenly-distributed high-intensity interval training within a polarized microcycle2017In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 8, no JUN, p. 1-12, article id 413Article in journal (Refereed)
    Abstract [en]

    Introduction: The current study aimed to investigate the responses to block- versus evenly-distributed high-intensity interval training (HIT) within a polarized microcycle. Methods: Twenty well-trained junior cross-country skiers (10 males, age 17.6 ± 1.5 and 10 females, age 17.3 ± 1.5) completed two, 3-week periods of training (EVEN and BLOCK) in a randomized, crossover-design study. In EVEN, 3 HIT sessions (5 × 4-min of diagonal-stride roller-skiing) were completed at a maximal sustainable intensity each week while low-intensity training (LIT) was distributed evenly around the HIT. In BLOCK, the same 9 HIT sessions were completed in the second week while only LIT was completed in the first and third weeks. Heart rate (HR), session ratings of perceived exertion (sRPE), and perceived recovery (pREC) were recorded for all HIT and LIT sessions, while distance covered was recorded for each HIT interval. The recovery-stress questionnaire for athletes (RESTQ-Sport) was completed weekly. Before and after EVEN and BLOCK, resting saliva and muscle samples were collected and an incremental test and 600-m time-trial (TT) were completed. Results: Pre- to post-testing revealed no significant differences between EVEN and BLOCK for changes in resting salivary cortisol, testosterone, or IgA, or for changes in muscle capillary density, fiber area, fiber composition, enzyme activity (CS, HAD, and PFK) or the protein content of VEGF or PGC-1α. Neither were any differences observed in the changes in skiing economy, VO2max or 600-m time-trial performance between interventions. These findings were coupled with no significant differences between EVEN and BLOCK for distance covered during HIT, summated HR zone scores, total sRPE training load, overall pREC or overall recovery-stress state. However, 600-m TT performance improved from pre- to post-training, irrespective of intervention (P = 0.003), and a number of hormonal and muscle biopsy markers were also significantly altered post-training (P < 0.05). Discussion: The current study shows that well-trained junior cross-country skiers are able to complete 9 HIT sessions within 1 week without compromising total work done and without experiencing greater stress or reduced recovery over a 3-week polarized microcycle. However, the findings do not support block-distributed HIT as a superior method to a more even distribution of HIT in terms of enhancing physiological or performance adaptions.

  • 19.
    Ortenblad, Niels
    et al.
    Univ Southem Denmark, Odense, Denmark; Univ British Columbia, Vancouver, BC, Canada.
    Nielsen, Joachim
    Univ Southem Denmark, Odense, Denmark.
    Boushel, Robert
    Univ British Columbia, Vancouver, BC, Canada.
    Söderlund, Karin
    Swedish Sch Sport & Hlth Sci, Astrand Lab, Stockholm.
    Saltin, Bengt
    Copenhagen Muscle Res Ctr, Copenhagen, Denmark.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. UiT Arctic Univ Norway, Sch Sport Sci, Tromso, Norway.
    The Muscle Fiber Profiles, Mitochondrial Content, and Enzyme Activities of the Exceptionally Well-Trained Arm and Leg Muscles of Elite Cross-Country Skiers2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, no AUG, article id 1031Article in journal (Refereed)
    Abstract [en]

    As one of the most physically demanding sports in the Olympic Games, cross-country skiing poses considerable challenges with respect to both force generation and endurance during the combined upper-and lower-body effort of varying intensity and duration. The isoforms of myosin in skeletal muscle have long been considered not only to define the contractile properties, but also to determine metabolic capacities. The current investigation was designed to explore the relationship between these isoforms and metabolic profiles in the arms (triceps brachii) and legs (vastus lateralis) as well as the range of training responses in the muscle fibers of elite cross-country skiers with equally and exceptionally well-trained upper and lower bodies. The proportion of myosin heavy chain (MHC)-1 was higher in the leg (58 +/- 2% [34-69%]) than arm (40 +/- 3% [24-57%]), although the mitochondrial volume percentages [8.6 +/- 1.6 (leg) and 9.0 +/- 2.0 (arm)], and average number of capillaries per fiber [5.8 +/- 0.8 (leg) and 6.3 +/- 0.3 (arm)] were the same. In these comparable highly trained leg and arm muscles, the maximal citrate synthase (CS) activity was the same. Still, 3-hydroxy-acyl-CoA-dehydrogenase (HAD) capacity was 52% higher (P < 0.05) in the leg compared to arm muscles, suggesting a relatively higher capacity for lipid oxidation in leg muscle, which cannot be explained by the different fiber type distributions. For both limbs combined, HAD activity was correlated with the content of MHC-1 (r(2) = 0.32, P = 0.011), whereas CS activity was not. Thus, in these highly trained cross-country skiers capillarization of and mitochondrial volume in type 2 fiber can be at least as high as in type 1 fibers, indicating a divergence between fiber type pattern and aerobic metabolic capacity. The considerable variability in oxidative metabolism with similar MHC profiles provides a new perspective on exercise training. Furthermore, the clear differences between equally well-trained arm and leg muscles regarding HAD activity cannot be explained by training status or MHC distribution, thereby indicating an intrinsic metabolic difference between the upper and lower body. Moreover, trained type 1 and type 2A muscle fibers exhibited similar aerobic capacity regardless of whether they were located in an arm or leg muscle.

  • 20.
    Pellegrini, Barbara
    et al.
    CeRiSM Res Ctr Mt Sport & Hlth, Rovereto, Italy; Univ Verona, Verona, Italy.
    Stöggl, Thomas Leonhard
    Univ Salzburg, Salzburg, Austria.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. UiT Arctic Univ Norway, Tromso, Norway.
    Developments in the Biomechanics and Equipment of Olympic Cross-Country Skiers2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, no JUL, article id 976Article in journal (Refereed)
    Abstract [en]

    Here, our aim was to describe the major changes in cross-country (XC) skiing in recent decades, as well as potential future developments. XC skiing has been an Olympic event since the very first Winter Games in Chamonix, France, in 1924. Over the past decades, considerable developments in skiing techniques and improvements in equipment and track preparation have increased skiing speed. In contrast to the numerous investigations on the physiological determinants of successful performance, key biomechanical factors have been less explored. Today's XC skier must master a wide range of speeds, terrains, and race distances and formats (e.g., distance races with individual start, mass-start or pursuit; knock-out and team-sprint; relays), continuously adapting by alternating between various sub-techniques. Moreover, several of the new events in which skiers compete head-to-head favor technical and tactical flexibility and encourage high-speed techniques (including more rapid development of propulsive force and higher peak forces), as well as appropriate training. Moreover, the trends toward more extensive use of double poling and skiing without grip wax in classical races have given rise to regulations in connection with Olympic distances that appear to have preserved utilization of the traditional classical sub-techniques. In conclusion, although both XC equipment and biomechanics have developed significantly in recent decades, there is clearly room for further improvement. In this context as well, for analyzing performance and optimizing training, sensor technology has a potentially important role to play.

  • 21.
    Pojskic, Haris
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Erik, Åslin
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Krolo, Ante
    Faculty of Kinesiology, University of Split, Split, Croatia.
    Jukic, Ivan
    Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia.
    Uljevic, Ognjen
    Faculty of Kinesiology, University of Split, Split, Croatia.
    Spasic, Miodrag
    Faculty of Kinesiology, University of Split, Split, Croatia.
    Sekulic, Damir
    Faculty of Kinesiology, University of Split, Croatia.
    Importance of Reactive Agility and Change of Direction Speed in Differentiating Performance Levels in Junior Soccer Players: Reliability and Validity of Newly Developed Soccer-Specific Tests2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, no MAY, article id 506Article in journal (Refereed)
    Abstract [en]

    Agility is a significant determinant of success in soccer; however, studies have rarely presented and evaluated soccer-specific tests of reactive agility (S_RAG) and non-reactive agility (change of direction speed – S_CODS) or their applicability in this sport. The aim of this study was to define the reliability and validity of newly developed tests of the S_RAG and S_CODS to discriminate between the performance levels of junior soccer players. The study consisted of 20 players who were involved at the highest national competitive rank (all males; age: 17.0 0.9 years), divided into three playing positions (defenders, midfielders, and forwards) and two performance levels(U17 and U19). Variables included body mass (BM), body height, body fat percentage,20-m sprint, squat jump, countermovement jump, reactive-strength-index, unilateral jump, 1RM-back-squat, S_CODS, and three protocols of S_RAG. The reliabilities of theS_RAG and S_CODS were appropriate to high (ICC: 0.70 to 0.92), with the strongest reliability evidenced for the S_CODS. The S_CODS and S_RAG shared 25–40% of the common variance. Playing positions significantly differed in BM (large effect-size differences [ES]; midfielders were lightest) and 1RM-back-squat (large ES; lowest results in midfielders). The performance levels significantly differed in age and experience in soccer; U19 achieved better results in the S_CODS (t-test: 3.61, p < 0.05, large ES)and two S_RAG protocols (t-test: 2.14 and 2.41, p < 0.05, moderate ES). Newly developed tests of soccer-specific agility are applicable to differentiate U17 and U19players. Coaches who work with young soccer athletes should be informed that the development of soccer-specific CODS and RAG in this age is mostly dependent on training of the specific motor proficiency.

  • 22.
    Pojskic, Haris
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Linnaeus Univ, Kalmar.
    Eslami, Bahareh
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Relationship Between Obesity, Physical Activity, and Cardiorespiratory Fitness Levels in Children and Adolescents in Bosnia and Herzegovina: An Analysis of Gender Differences2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, article id 1734Article in journal (Refereed)
    Abstract [en]

    This study aimed to examine: (i) the level of physical activity (PA), obesity indices and cardiorespiratory fitness (CRF) among boys and girls in primary school, and (ii) to determine the association of obesity indices and PA with CRF for the total number of participants, and then separately for boys and girls. 753 sixth to ninth grade girls and boys aged 10-14 years took part in this cross-sectional study. The PA was assessed by the "Physical Activity Questionnaire - Children" and CRF was assessed by the Maximal multistage a 20 m shuttle run test. Body mass index (BMI), waist circumferences (WC), and waist to height ratio (WHtR) were considered as obesity indices. Multiple linear regression analyses were performed to explore correlates of CRF. The results obtained showed the prevalence of general overweight and obesity was 25.5% in our sample which was lower than that in the regional estimate (e.g., similar to 28%) for Eastern Europe. Among all participants, CRF was associated with male sex, older age, a lower WC percentile, higher WHtR, and higher level of PA. The model accounted for 24% of the variance. CRF was associated with older age and higher level of PA among girls and boys. Lower WC percentile was a significant determinant of CRF among boys. In conclusion, general overweight/obesity was not independently associated with CRF. Those with better CRF were more likely to be male and older, had a higher level of PA and lower central adiposity. These findings emphasize the importance of supporting school age children to take a part in programmed physical activity regardless of their body composition.

  • 23.
    Sperlich, B
    et al.
    University of Würzburg.
    De Clerck, Ine
    Artevelde University College Ghent, Ghent, Belgium.
    Zinner, Christoph
    Department of Sport, University of Applied Sciences for Police and Administration of Hesse, Wiesbaden, Germany.
    Holmberg, Hans-Christer
    Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden.
    Wallmann-Sperlich, Birgit
    University of Würzburg.
    Prolonged Sitting Interrupted by 6-Min of High-Intensity Exercise: Circulatory, Metabolic, Hormonal, Thermal, Cognitive, and Perceptual Responses2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, article id 1279Article in journal (Refereed)
    Abstract [en]

    The aim was to examine certain aspects of circulatory, metabolic, hormonal,

    thermoregulatory, cognitive, and perceptual responses while sitting following a brief

    session of high-intensity interval exercise. Twelve students (five men; age, 22

    2 years) performed two trials involving either simply sitting for 180 min (SIT) or sitting for this same period with a 6-min session of high-intensity exercise after 60 min (SIT CHIIT).

    At T0 (after 30 min of resting), T1 (after a 20-min breakfast), T2 (after sitting for 1 h),

    T3 (immediately after the HIIT), T4, T5, T6, and T7 (30, 60, 90, and 120 min after

    the HIIT), circulatory, metabolic, hormonal, thermoregulatory, cognitive, and perceptual

    responses were assessed. The blood lactate concentration (at T3–T5), heart rate (at

    T3–T6), oxygen uptake (at T3–T7), respiratory exchange ratio, and sensations of heat

    (T3–T5), sweating (T3, T4) and odor (T3), as well as perception of vigor (T3–T6), were

    higher and the respiratory exchange ratio (T4–T7) and mean body and skin temperatures

    (T3) lower in the SITCHIIT than the SIT trial. Levels of blood glucose and salivary cortisol,

    cerebral oxygenation, and feelings of anxiety/depression, fatigue or hostility, as well as

    the variables of cognitive function assessed by the Stroop test did not differ between

    SIT and SITCHIIT. In conclusion, interruption of prolonged sitting with a 6-min session

    of HIIT induced more pronounced circulatory and metabolic responses and improved

    certain aspects of perception, without affecting selected hormonal, thermoregulatory or

    cognitive functions.

  • 24.
    Sperlich, B
    et al.
    University of Ljubljana, Ljubljana, Slovenia.
    Ogrin, J
    University of Ljubljana, Ljubljana, Slovenia.
    Holmberg, Hans-Christer
    UiT Arctic University of Norway; University of British Columbia, Vancouver, BC, Canada; Karolinska Institutet, Stockholm, Sweden.
    Whole-Body Vibrations Associated With Alpine Skiing: A Risk Factor for Low Back Pain?2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, article id 204Article in journal (Refereed)
    Abstract [en]

    Alpine skiing, both recreational and competitive, is associated with high rates of injury. Numerous studies have shown that occupational exposure to whole-body vibrations is strongly related to lower back pain and some suggest that, in particular, vibrations of lower frequencies could lead to overuse injuries of the back in connection with alpine ski racing. However, it is not yet known which forms of skiing involve stronger vibrations and whether these exceed safety thresholds set by existing standards and directives. Therefore, this study was designed to examine whole-body vibrations connected with different types of skiing and the associated potential risk of developing low back pain. Eight highly skilled ski instructors, all former competitive ski racers and equipped with five accelerometers and a Global Satellite Navigation System to measure vibrations and speed, respectively, performed six different forms of skiing: straight running, plowing, snow-plow swinging, basic swinging, short swinging, and carved turns. To estimate exposure to periodic, random and transient vibrations the power spectrum density (PSD) and standard ISO 2631-1:1997 parameters [i.e., the weighted root-mean-square acceleration (RMS), crest factor, maximum transient vibration value and the fourth-power vibration dose value (VDV)] were calculated. Ground reaction forces were estimated from data provided by accelerometers attached to the pelvis. The major novel findings were that all of the forms of skiing tested produced whole-body vibrations, with highest PSD values of 1.5–8 Hz. Intensified PSD between 8.5 and 35 Hz was observed only when skidding was involved. The RMS values for 10 min of short swinging or carved turns, as well as all 10-min equivalent VDV values exceeded the limits set by European Directive 2002/44/EC for health and safety. Thus, whole-body vibrations, particularly in connection with high ground reaction forces, contribute to a high risk for low back pain among active alpine skiers.

  • 25.
    Sperlich, Billy
    et al.
    Univ Wurzburg, Wurzburg, Germany.
    Düking, Peter
    Univ Wurzburg, Wurzburg, Germany.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. UiT Arctic Univ Norway, Tromso, Norway; Univ British Columbia, Vancouver, Canada.
    A SWOT Analysis of the Use and Potential Misuse of Implantable Monitoring Devices by Athletes2017In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 8, no SEP, article id 629Article in journal (Other academic)
  • 26.
    Sperlich, Billy
    et al.
    Univ Wurzburg, Inst Sport Sci, Integrat & Expt Exercise Sci & Training, Wurzburg, Germany.
    Hahn, Lea-Sofie
    Univ Wurzburg, Inst Sport Sci, Integrat & Expt Exercise Sci & Training, Wurzburg, Germany.
    Edel, Antonia
    Univ Wurzburg, Inst Sport Sci, Integrat & Expt Exercise Sci & Training, Wurzburg, Germany.
    Behr, Tino
    Univ Wurzburg, Inst Sport Sci, Integrat & Expt Exercise Sci & Training, Wurzburg, Germany.
    Helmprobst, Julian
    Univ Wurzburg, Inst Sport Sci, Integrat & Expt Exercise Sci & Training, Wurzburg, Germany.
    Leppich, Robert
    Univ Wurzburg, Inst Sport Sci, Integrat & Expt Exercise Sci & Training, Wurzburg, Germany.
    Wallmann-Sperlich, Birgit
    Univ Wurzburg, Inst Sport Sci, Wurzburg, Germany.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Univ British Columbia, Sch Kinesiol, Vancouver, BC, Canada; UiT Arctic Univ Norway, Sch Sport Sci, Tromso, Norway.
    A 4-Week Intervention Involving Mobile-Based Daily 6-Minute Micro-Sessions of Functional High-Intensity Circuit Training Improves Strength and Quality of Life, but Not Cardio-Respiratory Fitness of Young Untrained Adults2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, article id e423Article in journal (Refereed)
    Abstract [en]

    The present study was designed to assess the psycho-physiological responses of physically untrained individuals to mobile-based multi-stimulating, circuit-like, multiplejoint conditioning (CircuitHiu) performed either once (IxCircuitmu) or twice (2xCircuitHiu) daily for 4 weeks. In this single-center, two-arm randomized, controlled study, 24 men and women (age: 25 +/- 5 years) first received no training instructions for 4 weeks and then performed 4 weeks of either IxCircuitnirr or 2xCircuitHiu (5 men and 7 women in each group) daily. The IxCircuitnirr and 2xCircuitHiu participants carried out 90.7 and 85.7% of all planned training sessions, respectively, with average heart rates during the 6-min sessions of 74.3 and 70.8% of maximal heart rate. Body, fat and fat-free mass, and metabolic rate at rest did not differ between the groups or between time-points of measurement. Heart rate while running at 6 km h(-1) declined after the intervention in both groups. Submaximal and peak oxygen uptake, the respiratory exchange ratio and heart rate recovery were not altered by either intervention. The maximal numbers of push-ups, leg-levers, burpees, 45 degrees-one-legged squats and 30-s skipping, as well as perception of general health improved in both groups. Our IxCircuitHiu or 2xCircuitHiiT interventions improved certain parameters of functional strength and certain dimensions of quality of life in young untrained individuals. However, they were not sufficient to enhance cardio-respiratory fitness, in particular peak oxygen uptake.

  • 27.
    Sperlich, Billy
    et al.
    Univ Wurzburg, Wurzburg, Germany.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. UiT Arctic Univ Norway, Tromso, Norway; Univ British Columbia, Vancouver, Canada.
    The Responses of Elite Athletes to Exercise: An All-Day, 24-h Integrative View Is Required!2017In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 8, article id 564Article in journal (Other academic)
  • 28.
    Sperlich, Billy
    et al.
    University of Wurzburg, Germany.
    Wallman-Sperlich, Birgit
    University of Wurzburg, Germany.
    Zinner, Christoph
    University of Wurzburg, Germany.
    Von Stauffenberg, Valerie
    University of Wurzburg, Germany.
    Losert, Helena
    University of Wurzburg, Tyskland.
    Holmberg, Hans-Christer
    School of Sport Sciences, University of Tromsø, Norway.
    Functional High-Intensity Circuit Training Improves Body Composition, Peak Oxygen Uptake, Strength, and Alters Certain Dimensions of Quality of Life in Overweight Women2017In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 8, article id 172Article in journal (Refereed)
    Abstract [en]

    The effects of circuit-like functional high-intensity training (CircuitHIIT) alone or in combination with high-volume low-intensity exercise (Circuitcombined) on selected cardio-respiratory and metabolic parameters, body composition, functional strength and the quality of life of overweight women were compared. In this single-center, two-armed randomized, controlled study, overweight women performed 9-weeks (3 sessions·wk-1) of either CircuitHIIT (n = 11), or Circuitcombined (n = 8). Peak oxygen uptake and perception of physical pain were increased to a greater extent (p < 0.05) by CircuitHIIT, whereas Circuitcombined improved perception of general health more (p < 0.05). Both interventions lowered body mass, body-mass-index, waist-to-hip ratio, fat mass, and enhanced fat-free mass; decreased ratings of perceived exertion during submaximal treadmill running; improved the numbers of push-ups, burpees, one-legged squats, and 30-s skipping performed, as well as the height of counter-movement jumps; and improved physical and social functioning, role of physical limitations, vitality, role of emotional limitations, and mental health to a similar extent (all p < 0.05). Either forms of these multi-stimulating, circuit-like, multiple-joint training can be employed to improve body composition, selected variables of functional strength, and certain dimensions of quality of life in overweight women. However, CircuitHIIT improves peak oxygen uptake to a greater extent, but with more perception of pain, whereas Circuitcombined results in better perception of general health.

  • 29.
    Stöggl, Thomas
    et al.
    University of Salzburg, Salzburg, Austria.
    Björklund, Glenn
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. The Swedish Sports Confederation, Stockholm, Sweden.
    High intensity interval training leads to greater improvements in acute heart rate recovery and anaerobic power as high volume low intensity training2017In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 8, article id 562Article in journal (Refereed)
    Abstract [en]

    The purpose of the current study was to explore if training regimes utilizing diverse training intensity distributions result in different responses on neuromuscular status, anaerobic capacity/power and acute heart rate recovery (HRR) in well-trained endurance athletes.

    Methods: Thirty-six male (n = 33) and female (n = 3) runners, cyclists, triathletes and cross-country skiers [peak oxygen uptake: (VO2peak): 61.9 ± 8.0 mL·kg−1·min−1] were randomly assigned to one of three groups (blocked high intensity interval training HIIT; polarized training POL; high volume low intensity oriented control group CG/HVLIT applying no HIIT). A maximal anaerobic running/cycling test (MART/MACT) was performed prior to and following a 9-week training period.

    Results: Only the HIIT group achieved improvements in peak power/velocity (+6.4%, P < 0.001) and peak lactate (P = 0.001) during the MART/MACT, while, unexpectedly, in none of the groups the performance at the established lactate concentrations (4, 6, 10 mmol·L−1) was changed (P > 0.05). Acute HRR was improved in HIIT (11.2%, P = 0.002) and POL (7.9%, P = 0.023) with no change in the HVLIT oriented control group.

    Conclusion: Only a training regime that includes a significant amount of HIIT improves the neuromuscular status, anaerobic power and the acute HRR in well-trained endurance athletes. A training regime that followed more a low and moderate intensity oriented model (CG/HVLIT) had no effect on any performance or HRR outcomes.

  • 30.
    Stöggl, Thomas
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Department of Sport Science and Kinesiology, University of Salzburg, Salzburg, Austria .
    Sperlich, B.
    Institute of Sport Science, University of Würzburg, Würzburg, Germany .
    Polarized training has greater impact on key endurance variables than threshold, high intensity, or high volume training2014In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 5, p. Art. no. 33-Article in journal (Refereed)
    Abstract [en]

    Endurance athletes integrate four conditioning concepts in their training programs: high-volume training (HVT), "threshold-training" (THR), high-intensity interval training (HIIT) and a combination of these aforementioned concepts known as polarized training (POL). The purpose of this study was to explore which of these four training concepts provides the greatest response on key components of endurance performance in well-trained endurance athletes. Methods: Forty eight runners, cyclists, triathletes, and cross-country skiers (peak oxygen uptake: (VO2peak): 62.6 ± 7.1 mL·min-1·kg-1) were randomly assigned to one of four groups performing over 9 weeks. An incremental test, work economy and a VO2peak tests were performed. Training intensity was heart rate controlled. Results: POL demonstrated the greatest increase in VO2peak (+6.8 ml·min·kg-1 or 11.7%, P &lt; 0.001), time to exhaustion during the ramp protocol (+17.4%, P &lt; 0.001) and peak velocity/power (+5.1%, P &lt; 0.01). Velocity/power at 4 mmol·L-1 increased after POL (+8.1%, P &lt; 0.01) and HIIT (+5.6%, P &lt; 0.05). No differences in pre- to post-changes of work economy were found between the groups. Body mass was reduced by 3.7% (P &lt; 0.001) following HIIT, with no changes in the other groups. With the exception of slight improvements in work economy in THR, both HVT and THR had no further effects on measured variables of endurance performance (P &gt; 0.05). Conclusion: POL resulted in the greatest improvements in most key variables of endurance performance in well-trained endurance athletes. THR or HVT did not lead to further improvements in performance related variables. © 2014 Stöggl and Sperlich.

  • 31.
    Supej, Matej
    et al.
    Univ Ljubljana, Ljubljana, Slovenia.
    Holmberg, Hans-Christer
    UiT Arctic Univ Norway, Tromso, Norway.
    Recent Kinematic and Kinetic Advances in Olympic Alpine Skiing: Pyeongchang and Beyond2019In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 10, no FEB, article id 111Article in journal (Refereed)
    Abstract [en]

    Alpine skiing has been an Olympic event since the first Winter Games in 1936. Nowadays, skiers compete in four main events: slalom, giant slalom, super-G and downhill. Here, we present an update on the biomechanics of alpine ski racers and their equipment. The technical and tactical ability of today's world-class skiers have adapted substantially to changes in equipment, snow conditions and courses. The wide variety of terrain, slopes, gate setups and snow conditions involved in alpine skiing requires skiers to continuously adapt, alternating between the carving and skidding turning techniques. The technical complexity places a premium on minimizing energy dissipation, employing strategies and ski equipment that minimize ski-snow friction and aerodynamic drag. Access to multiple split times along the racing course, in combination with analysis of the trajectory and speed provide information that can be utilized to enhance performance. Peak ground reaction forces, which can be as high as five times body weight, serve as a measure of the external load on the skier and equipment. Although the biomechanics of alpine skiing have significantly improved, several questions concerning optimization of skiers' performance remain to be investigated. Recent advances in sensor technology that allow kinematics and kinetics to be monitored can provide detailed information about the biomechanical factors related to success in competitions. Moreover, collection of data during training and actual competitions will enhance the quality of guidelines for training future Olympic champions. At the same time, the need to individualize training and skiing equipment for each unique skier will motivate innovative scientific research for years to come.

  • 32.
    Zinner, Christoph
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Univ Wurzburg, Dept Sport Sci, Wurzburg, Germany.
    Morales-Alamo, David
    Univ Las Palmas Gran Canaria, Las Palmas Gran Canaria, Spain.
    Örtenblad, Niels
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Univ Southern Denmark, Inst Sports Sci & Clin Biomech, Odense, Denmark.
    Larsen, Filip J.
    Swedish Sch Sport & Hlth Sci, Stockholm.
    Schiffer, Tomas A.
    Linköping Univ, Dept Med & Hlth Sci, Linköping.
    Willis, Sarah J.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Gelabert-Rebato, Miriam
    Univ British Columbia, Sch Kinesiol, Vancouver, BC, Canada.
    Perez-Valera, Mario
    Univ Las Palmas Gran Canaria, Las Palmas Gran Canaria, Spain.
    Boushel, Robert
    Univ British Columbia, Sch Kinesiol, Vancouver, BC, Canada.
    Calbet, Jose A. L.
    Univ British Columbia, Sch Kinesiol, Vancouver, BC, Canada; Univ Las Palmas Gran Canaria, Las Palmas Gran Canaria, Spain.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Univ British Columbia, Sch Kinesiol, Vancouver, BC, Canada; UiT Arctic Univ Norway, Sch Sport Sci, Tromso, Norway.
    The Physiological Mechanisms of Performance Enhancement with Sprint Interval Training Differ between the Upper and Lower Extremities in Humans2016In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 7, no SEP, article id 426Article in journal (Refereed)
    Abstract [en]

    To elucidate the mechanisms underlying the differences in adaptation of arm and leg muscles to sprint training, over a period of 11 days 16 untrained men performed six sessions of 4-6 x 30-s all-out sprints (SIT) with the legs and arms, separately, with a 1-h interval of recovery. Limb-specific VO(2)peak, sprint performance (two 30-s Wingate tests with 4-min recovery), muscle efficiency and time-trial performance (TT, 5-min all-out) were assessed and biopsies from the m. vastus lateralis and m. triceps brachii taken before and after training. VO(2)peak and Wmax increased 3-11% after training, with a more pronounced change in the arms (P < 0.05). Gross efficiency improved for the arms (+8.8%, P < 0.05), but not the legs (-0.6%). Wingate peak and mean power outputs improved similarly for the arms and legs, as did TT performance. After training, VO2 during the two Wingate tests was increased by 52 and 6% for the arms and legs, respectively (P < 0.001). In the case of the arms, VO2 was higher during the first than second Wingate test (64 vs. 44%, P < 0.05). During the TT, relative exercise intensity, HR, VO2, VCO2, V-E, and V-t were all lower during arm-cranking than leg-pedaling, and oxidation of fat was minimal, remaining so after training. Despite the higher relative intensity, fat oxidation was 70% greater during leg-pedaling (P = 0.017). The aerobic energy contribution in the legs was larger than for the arms during the Wingate tests, although VO2 for the arms was enhanced more by training, reducing the O-2 deficit after SIT. The levels of muscle glycogen, as well as the myosin heavy chain composition were unchanged in both cases, while the activities of 3-hydroxyacyl-CoA-dehydrogenase and citrate synthase were elevated only in the legs and capillarization enhanced in both limbs. Multiple regression analysis demonstrated that the variables that predict TT performance differ for the arms and legs. The primary mechanism of adaptation to SIT by both the arms and legs is enhancement of aerobic energy production. However, with their higher proportion of fast muscle fibers, the arms exhibit greater plasticity.

  • 33.
    Zoppirolli, Chiara
    et al.
    CeRiSM Res Ctr Sport Mt & Hlth, Rovereto, Italy; Univ Verona, Verona, Italy.
    Bortolan, Lorenzo
    CeRiSM Res Ctr Sport Mt & Hlth, Rovereto, Italy; Univ Verona, Verona, Italy.
    Stella, Federico
    CeRiSM Res Ctr Sport Mt & Hlth, Rovereto, Italy; Univ Verona, Verona, Italy.
    Boccia, Gennaro
    Univ Turin, NeuroMuscularFunct Res Grp, Turin, Italy.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. UiT Arctic Univ Norway, Tromso, Norway.
    Schena, Federico
    CeRiSM Res Ctr Sport Mt & Hlth, Rovereto, Italy; Univ Verona, Verona, Italy.
    Pellegrini, Barbara
    CeRiSM Res Ctr Sport Mt & Hlth, Rovereto, Italy; Univ Verona, Verona, Italy.
    Following a Long-Distance Classical Race the Whole-Body Kinematics of Double Poling by Elite Cross-Country Skiers Are Altered2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, no JUL, article id 978Article in journal (Refereed)
    Abstract [en]

    Introduction: Although short-term (approximately 10-min) fatiguing DP has been reported not to alter the joint kinematics or displacement of the centre of mass (COM) of high-level skiers, we hypothesize that prolonged DP does change these kinematics, since muscular strength is impaired following endurance events lasting longer than 2 h. Methods: During the 58-km Marcialonga race in 2017, the fastest 15 male skiers were videofilmed (100 fps, FHD resolution in the sagittal plane) on two 20-m sections (inclines: 0.7 +/- 0.1 degrees) 48 km apart (i.e., 7 and 55 km from the start), approximating 50-km Olympic races. The cameras were positioned perpendicular to and about 40 m from the middle of each section and spatial dimensions adjusted for each individual track skied. Pole and joint kinematics, as well as displacement of the COM during two DP cycles were assessed. Results: The 10 skiers who fulfilled our inclusion criteria finished the race in 2 h 09 min 19 s +/- 28 s. Displacements of the joints and COM were comparable to previous observations on skiers roller skiing on a flat treadmill at similar speeds in the laboratory. 55 km after the start, cycle velocity and length were lower (P < 0.001 and P = 0.002, respectively) and the angular range of elbow joint flexion during the initial part of the poling phase reduced, while shoulder angle was greater during the first 35% of the DP cycle (all P < 0.05). Moreover, the ankle angle was increased and forward displacement of the COM reduced during the first 80% of the cycle. Conclusion: Prolonged DP reduced the forward displacement of the COM and altered arm kinematics during the early poling phase. The inefficient utilization of COM observed after 2 h of competition together with potential impairment of the stretch-shortening of arm extensor muscles probably attenuated generation of poling force. To minimize these effects of fatigue, elite skiers should focus on maintaining optimal elbow and ankle kinematics and an effective forward lean during the propulsive phase of DP.

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