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  • 1.
    Ainegren, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Roller skis' rolling resistance and grip characteristics: influences on physiological and performance measures in cross-country skiers2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aim of this thesis was to investigate roller ski characteristics; classical and freestyle roller skis’ rolling resistance coefficients (μR) and classical style roller skis’ static friction coefficients (μS), and to study the influence of different μR and μS on cross-country skiers’ performance and both physiological and biomechanical indices. The aim was also to study differences in skiing economy and efficiency between recreational skiers, female and male junior and senior elite cross-country skiers.The experiments showed that during a time period of 30 minutes of rolling on a treadmill (warm-up), μR decreased significantly (p<0.05) to about 60-65 % and 70-75 % of its initial value for freestyle and classical roller skis respectively. Also, there was a significant influence of normal force on μR, while different velocities and inclinations of the treadmill only resulted in small changes in μR.The study of the influence on physiological variables of a ~50 % change in μR showed that during submaximal steady rate exercise, external power, oxygen uptake, heart rate and blood lactate were significantly changed, while there were non-significant or only small changes to cycle rate, cycle length and ratings of perceived exertion. Incremental maximal tests showed that time to exhaustion was significantly changed and this occurred without a change in maximal power, maximal oxygen uptake, maximal heart rate and blood lactate, and that the influence on ratings of perceived exertion was non-significant or small.The study of classical style roller skis μS showed values that were five to eight times more than the values of μS reported from on-snow skiing with grip-waxed cross-country skis.The subsequent physiological and biomechanical experiments with different μS showed a significantly lower skiing economy (~14 % higher v̇O2), higher heart rate, lower propulsive forces coming from the legs and shorter time to exhaustion (~30 %) when using a different type of roller ski with a μS similar to on-snow skiing, while there was no difference between tests when using different pairs of roller skis with a (similar) higher μS.The part of the thesis which focused on skiing economy and efficiency as a function of skill, age and gender, showed that the elite cross-country skiers had better skiing economy and higher gross efficiency (5-18 %) compared with the recreational skiers, and the senior elite had better economy and higher efficiency (4-5 %) than their junior counterparts, while no differences could be found between the genders.

  • 2.
    Ainegren, Mats
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Ainegren, Mats
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Carlsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Roller ski rolling resistance and its effects on elite athletes’ performance2008In: ENGINEERING OF SPORT 7, VOL 2, 2008, Vol. 11, no 3, p. 393-400Conference paper (Refereed)
    Abstract [en]

    Modern ski-treadmills allow cross-country skiers, biathletes and ski-orienteers to test their physical fitness in a laboratory environment whilst performing classical and freestyle (skating) techniques on roller skis. For elite athletes the differences in performance between test occasions are quite small, thus emphasising the importance of knowing the roller skis’ rolling resistance in order to allow the correct comparison between the results of different test occasions. In this study the roller skis’ rolling resistance has been measured using equipment on the ski-treadmill. The study investigates the influence of significant changes in rolling resistance on physiological variables. The results show that during submaximal exercise, heart rate, blood lactate, power and oxygen uptake are significantly changed by different rolling resistances, while there are no significant or only small changes to cycle rate, cycle length and ratings of perceived exertion. Incremental maximal tests show that time to exhaustion is significantly changed by different rolling resistances and this occurred without significant changes in maximal oxygen uptake and heart rate, and the influence on maximal power and ratings of perceived exertion were insignificant or small.

  • 3.
    Ainegren, Mats
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Ainegren, Mats
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Carlsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Roller ski rolling resistance and its effects on elite athletes’ performance2009In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 11, no 3, p. 143-157Article in journal (Refereed)
    Abstract [en]

    Modern ski-treadmills allow cross-country skiers, biathletes and ski-orienteers to test their physical fitness in a laboratory environment whilst performing classical and freestyle (skating) techniques on roller skis. For elite athletes, the differences in performance between test occasions are quite small, thus emphasising the importance of knowing the roller skis’ rolling resistance in order to allow the correct comparison between the results of different test occasions. In this study, the roller skis’ rolling resistance was measured on the ski-treadmill’s surface using a roller ski rolling resistance measurement system specially produced for this purpose. The study investigated the influence of significant changes in rolling resistance on physiological variables. The results showed that during submaximal exercise, power, oxygen uptake, heart rate and blood lactate were significantly changed by different rolling resistances, while there were no significant or only small changes to cycle rate, cycle length and ratings of perceived exertion. Incremental maximal tests showed that time to exhaustion was significantly changed by different rolling resistances and this occurred without significant changes in maximal power, maximal oxygen uptake, maximal heart rate and blood lactate, and that the influence on ratings of perceived exertion were insignificant or small.

     

  • 4.
    Ainegren, Mats
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Ainegren, Mats
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Carlsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Rolling resistance for treadmill roller skiing2008In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 11, no 1, p. 23-29Article in journal (Refereed)
    Abstract [en]

    Modern treadmills allow cross-country skiers, biathletes and ski-orienteers to test their physical performance under laboratory conditions using classical and freestyle techniques on roller skis. The differences in performance between tests are quite small for elite athletes, and it is therefore of great importance to control the rolling resistance of the roller skis. Otherwise different physiological tests cannot be accurately compared.

    This study shows that during a warm-up period of  30 minutes the coefficient of rolling resistance (µR) decreases to about 60-65% and 70-75% of its initial value for freestyle and classical roller skis respectively.

    Simultaneous measurements of temperature and µR shows that stabilized rolling resistance corresponds to a certain running temperature for a given normal force on the roller ski.

    Tests were also performed on the influence on µR of normal force, velocity and inclination. Normal forces produced significant influence on µR , while different velocities and inclinations of the treadmill only resulted in small changes in µR.

  • 5.
    Ainegren, Mats
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Carlsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Laaksonen, Marko S.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    The influence of grip on oxygen consumption and leg forces when using classical style roller skis2014In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 24, no 2, p. 301-310Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to investigate the influence of classical style roller skis' grip (static friction coefficients, μ S) on cross-country skiers' oxygen consumption and leg forces during treadmill roller skiing, when using the diagonal stride and kick double poling techniques. The study used ratcheted wheel roller skis from the open market and a uniquely designed roller ski with an adjustable camber and grip function. The results showed significantly (P≤0.05) higher oxygen consumption (∼14%), heart rate (∼7%), and lower propulsive forces from the legs during submaximal exercise and a shorter time to exhaustion (∼30%) in incremental maximal tests when using roller skis with a μ S similar to on-snow skiing, while there was no difference between tests when using different pairs of roller skis with a similar, higher μ S. Thus, we concluded that oxygen consumption (skiing economy), propulsive leg forces, and performance time are highly changed for the worse when using roller skis with a lower μ S, such as for on-snow skiing with grip-waxed cross-country skis, in comparison to ratcheted wheel roller skis with several times higher μ S.

  • 6.
    Ainegren, Mats
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Carlsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    An experimental study to compare the grip of classical style roller skis with on-snow skiing2013In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 16, no 2, p. 115-122Article in journal (Refereed)
    Abstract [en]

    Cross-country skiers use roller skis for their snow-free training with the aim of imitating skiing on snow. Also, exercise laboratories evaluate the biomechanics and physiology of cross-country skiing using roller skis on a treadmill. The roller skis on the market that are constructed for use in the classical style are equipped with a front and a back wheel, one of which has a ratchet to enable it to grip the surface when diagonal striding and kick double poling (static friction). The aim of this study was to investigate static friction coefficients (μS) of ratcheted wheel roller skis, and compare the results to the μS reported from skiing on snow with grip-waxed cross-country skis. Also, a new type of roller ski with a camber and adjustable grip function was evaluated. The results showed that ratcheted wheel roller skis, on a treadmill rubber mat and on dry and wet asphalt surfaces, reached μS values that were five to eight times greater than the values reported from on-snow skiing with grip-waxed cross-country skis. For the roller skis with a camber and adjustable grip function, the μs could be varied from no grip at all up to the level of the tested ratcheted wheel roller skis.

  • 7.
    Ainegren, Mats
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Carlsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Rolling resistance for treadmill roller skiing: Presented at International Congress on Science and Nordic Skiing 2006, June 18-20, 2006, Vuokatti, Finland2006Conference paper (Other academic)
  • 8.
    Ainegren, Mats
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Carlsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Laaksonen, Marko S.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Skiing economy and efficiency in recreational and elite cross-country skiers2013In: Journal of Strength and Conditioning Research, ISSN 1064-8011, E-ISSN 1533-4287, Vol. 27, no 5, p. 1239-1252Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to investigate and compare skiing economy and gross efficiency in cross-country skiers of different performance levels, ages and genders; male recreational skiers and elite senior and junior cross-country skiers of both genders. The skiers performed tests involving roller skiing on a treadmill using the gear 3 and diagonal stride techniques. The elite crosscountry skiers were found to have better skiing economy and higher gross efficiency (5-18%) compared with the recreational skiers (p < 0.05) and the senior elite had better economy and higher efficiency (4-5%) than their junior counterparts (p < 0.05), whereas no differences could be found between the genders. Also, large ranges in economy and gross efficiency were found in all groups. It was concluded that, in addition to v̇O2peak, skiing economy and gross efficiency have a great influence on the differences in performance times between recreational and junior and senior elite cross-country skiers, as well as between individual skiers within the different categories. Thus, we recommend crosscountry skiers at all performance levels to test not only v̇O2peak, but also skiing economy and efficiency.

  • 9. Alkner, Björn A
    et al.
    Tesch, Per A
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Knee extensor and plantar flexor muscle size and function following 90 days of bed rest with or without resistance exercise.2004In: European Journal of Applied Physiology, ISSN 1439-6319, Vol. 93, no 3, p. 294-305Article in journal (Refereed)
    Abstract [en]

    Skeletal muscle atrophy and strength loss induced by short-term simulated spaceflight are offset or attenuated by resistance exercise (RE). This study compared the effects of plantar flexor and knee extensor RE on muscle size and function in 17 healthy men (aged 26–41years) subjected to 90 days 6 head-down-tilt bed rest with (BRE; n=8) or without (BR; n=9) RE. The RE program consisted of coupled maximal concentric and eccentric actions in the supine squat (4 sets of 7 repetitions) and calf press (4·14) every third day employing a gravity-independent flywheel ergometer (FW). Prior to, and following bed rest, muscle volume was assessed using magnetic resonance imaging. Similarly, muscle strength and power and surface lectromyographic (EMG) activity were determined during maximal actions using FW or isokinetic dynamometry. In BR, knee extensor and plantar flexor muscle volume decreased (P<0.05) 18% and 29%, respectively. Torque or force and power decreased (P<0.05) 31–60% (knee extension) and 37–56% (plantar flexion) while knee extensor and plantar flexor EMG activity decreased 31–38% and 28–35%, respectively following BR. Muscle atrophy in BRE was prevented (P>0.05; knee extensors) or attenuated ()15%; plantar flexors). BRE maintained task-specific force, power and EMG activity. The decrease in non-task-specific torque was less (P<0.05) than in BR. The present data imply that the triceps surae and quadriceps muscles show different responsiveness to long-term bed rest with or without resistance exercise. The results also suggest that designing in-flight resistance exercise protocols for space travellers is complex and must extend beyond preserving

  • 10. Alkner, Björn
    et al.
    Tesch, Per A
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Efficacy of a gravity-independent resistance exercise device as a countermeasure to muscle atrophy during 29-day bed rest.2004In: Acta Physioloogica Scandinavica, ISSN 0001-6772, Vol. 181, no 3, p. 345-357Article in journal (Refereed)
    Abstract [en]

    This study determined changes in knee extensor and plantar flexor muscle volume during 29 days of bed rest with or without resistance exercise using a gravity-independent flywheel ergometer. METHODS: Seventeen men (26-41 years) were subjected to 29 days of bed rest with (n = 8) or without (n = 9) resistance exercise; Supine Squat (SS) and Calf Press (CP) performed every third day. Quadriceps and triceps surae muscle volume was determined before and after bed rest and force and power were measured during training. Prior to these interventions, reproducibility of this device for training and testing was assessed in 23 subjects who performed bilateral maximal concentric, eccentric and isometric (MVC) knee extensions and plantar flexions over repeated sessions with simultaneous measurements of force, power and electromyographic (EMG) activity. RESULTS: Quadriceps and triceps surae muscle volume decreased (P < 0.05) 10 and 16%, respectively, after 29 days bed rest. Exercise maintained quadriceps volume and mitigated triceps surae atrophy. Thus, either muscle showed different response across subject groups (P < 0.05). Force and power output during training were either maintained (P > 0.05) or increased (P < 0.05). EMG amplitude in the training mode was similar (SS; P > 0.05) or greater (CP; P < 0.05) compared with that elicited during MVC. Peak force and power test-retest coefficient of variation (CV) ranged 5-6% and 7-8% for SS and CP, respectively. CONCLUSION: The present data suggest that this resistance exercise paradigm counteracts quadriceps and abates the more substantial triceps surae muscle atrophy in bedridden subjects, and therefore should be an important asset to space travellers.

  • 11. Andersson, J
    et al.
    Biasoletto-Tjellström, G
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Reduced pulmonary oxygen uptake during apnea in resting humans: European Underwater and Baromedical Society (EUBS) meeting Copenhagen2003Conference paper (Other academic)
  • 12. Andersson, Johan
    et al.
    Linér, Mats
    Fredsted, Anne
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Cardiovascular and respiratory responses to apneas with and without face immersion in exercising humans2004In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 96, no 3, p. 1005-1010Article in journal (Refereed)
    Abstract [en]

    The effect of the diving response on alveolar gas exchange was investigated in 15 subjects. During steady-state exercise (80 W) on a cycle ergometer, the subjects performed 40-s apneas in air and 40-s apneas with face immersion in cold (10degreesC) water. Heart rate decreased and blood pressure increased during apneas, and the responses were augmented by face immersion. Oxygen uptake from the lungs decreased during apnea in air (-22% compared with eupneic control) and was further reduced during apnea with face immersion (-25% compared with eupneic control). The plasma lactate concentration increased from control (11%) after apnea in air and even more after apnea with face immersion (20%), suggesting an increased anaerobic metabolism during apneas. The lung oxygen store was depleted more slowly during apnea with face immersion because of the augmented diving response, probably including a decrease in cardiac output. Venous oxygen stores were probably reduced by the cardiovascular responses. The turnover times of these gas stores would have been prolonged, reducing their effect on the oxygen uptake in the lungs. Thus the human diving response has an oxygen-conserving effect.

  • 13. Andersson, Johan P A
    et al.
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Repeated apneas do not affect the hypercapnic ventilatory response in the short term2009In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 105, no 4, p. 569-74Article in journal (Refereed)
    Abstract [en]

    Long-term training of breath-hold diving reduces the hypercapnic ventilatory response (HCVR), an index of the CO(2) sensitivity. The aim of the present study was to elucidate whether also short-term apnea training (repeating apneas with short intervals) reduces the HCVR, thereby being one contributing factor explaining the progressively increasing breath-holding time (BHT) with repetition of apneas. Fourteen healthy volunteers performed a series of five maximal-duration apneas with face immersion and two measurements of the HCVR, using the Read rebreathing method. The BHT increased by 43% during the series of apneas (P < 0.001). However, the slope of the HCVR test was not affected by the series of apneas, being 2.52 (SD 1.27) and 2.24 (SD 1.14) l min(-1) mmHg(-1) in the control test and in the test performed within 2 min after the last apnea of the series, respectively (NS). Thus, a change in the HCVR cannot explain the observed short-term training effect on BHT.

  • 14.
    Andersson, Johan P.A.
    et al.
    Lunds universitet.
    Biasoletto-Tjellströma, Gustaf
    Schagatay, Erika K.A
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Pulmonary gas exchange is reduced by the cardiovascular diving response in resting humans2008In: Respiratory Physiology & Neurobiology, ISSN 1569-9048, E-ISSN 1878-1519, Vol. 160, no 3, p. 320-324Article in journal (Refereed)
    Abstract [en]

    The diving response reduces the pulmonary O2 uptake in exercising humans, but it has been debated whether this effect is present at rest. Therefore, respiratory and cardiovascular responses were recorded in 16 resting subjects, performing apnea in air and apnea with face immersion in cold water (10 ◦C). Duration of apneas were predetermined to be identical in both conditions (average: 145 s) and based on individual maximal capacity (average: 184 s). Compared to apnea in air, an augmented diving response was elicited by apnea with face immersion. The O2 uptake from the lungs was reduced compared to the resting eupneic control (4.6 ml min−1 kg−1), during apnea in air (3.6 ml min−1 kg−1) and even more so during apnea with face immersion (3.4 ml min−1 kg -1). We conclude that the cardiovascular djustments of the diving response reduces pulmonary gas exchange in resting humans, allowing longer apneas by preserving the lungs’ O2 store for use by vital organs.

  • 15.
    Andersson, Johan P.A.
    et al.
    Department of Animal Physiology, Lund University.
    Linér, Mats H.
    Lund University Hospital.
    Rünow, Elisabeth
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Diving response and arterial oxygen saturation during apnea and exercise in breath-hold divers2002In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 93, no 3, p. 882-886Article in journal (Refereed)
    Abstract [en]

    This study addressed the effects of apnea in air and apnea with face immersion in cold water (10°C) on the diving response and arterial oxygen saturation during dynamic exercise. Eight trained breath-hold divers performed steady-state exercise on a cycle ergometer at 100 W. During exercise, each subject performed 30-s apneas in air and 30-s apneas with face immersion. The heart rate and arterial oxygen saturation decreased and blood pressure increased during the apneas. Compared with apneas in air, apneas with face immersion augmented the heart rate reduction from 21 to 33% (P < 0.001) and the blood pressure increase from 34 to 42% (P < 0.05). The reduction in arterial oxygen saturation from eupneic control was 6.8% during apneas in air and 5.2% during apneas with face immersion (P < 0.05). The results indicate that augmentation of the diving response slows down the depletion of the lung oxygen store, possibly associated with a larger reduction in peripheral venous oxygen stores and increased anaerobiosis. This mechanism delays the fall in alveolar and arterial Po2 and, thereby, the development of hypoxia in vital organs. Accordingly, we conclude that the human diving response has an oxygen-conserving effect during exercise.

  • 16. Andersson, Johan
    et al.
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Arterial oxygen desaturation during apnea in humans.1998In: Undersea & Hyperbaric Medicine, ISSN 1066-2936, Vol. 25, no 1, p. 21-25Article in journal (Refereed)
    Abstract [en]

    We studied the effect of the human diving response, defined as bradycardia and reduced peripheral blood flow, on arterial hemoglobin desaturation. We induced a diving response of different magnitudes by using apnea in air and apnea with face immersion. Each of21 subjects performed five apneas in air and five apneas with face immersion in 10°C water. Periods of apnea in both conditions were of the same duration in any individual subject (average: 126.4 s) and the order of air and water was equally distributed among subjects. Heart rate, skin capillary blood flow, arterial blood pressure, arterial hemoglobin oxygen saturation during apneas, and end-tidal fractions of CO2 after apneas were recorded with non-invasive methods. The bradycardia and capillary blood flow reduction during apnea in air (7.8 and 37.7% change from control, respectively) were significantly potentiated by face immersion (13.6 and 55.9%, respectively). Arterial hemoglobin desaturated more during apnea in air (2.7%) compared to during apnea with face immersion (1.4%). We conclude that the potentiation of the human diving response with face immersion in cold water leads to a smaller decrease in arterial hemoglobin saturation, which may reflect an oxygen-conserving effect

  • 17. Andersson, Johan
    et al.
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Diving response and apneic time in humans. 1998In: Undersea & Hyperbaric Medicine, ISSN 1066-2936, Vol. 25, no 1, p. 13-19Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to compare apneic time with the human diving response, defined as heart rate (HR) reduction and reduced skin blood flow, in groups with varying degrees of breath-hold diving experience. Apneic time and HR reduction at apneas in air and apneas with face immersion in cold water were thus recorded in nine groups. Skin capillary blood flow was recorded in six of the groups. All subjects received the same information on maximizing apneic duration, and no information about their progress during the apneas. The longest apneas and the most pronounced cardiovascular adjustments were found in the young, trained divers. It was found that apneic time was significantly correlated to HR reduction among the nine groups (r = 0.94, P < 0.001), and to skin capillary blood flow reduction among the six groups where the parameter was measured (r = 0.82, P < 0.05). The correlation between HR reduction and skin capillary blood flow reduction was also significant (r = 0.85, P < 0.05). When the difference in HR reduction and apneic time between apneas in air and apneas with face immersion were compared in the nine groups, it was found that all groups reacted with a more pronounced HR reduction during apneas with face immersion. All groups without prior breath-hold diving experience were found to perform shorter apneas with face immersion than apneas in air, or apneas of the same duration in both conditions, which has been reported in other studies. However, in all groups with diving experience, the apneic time was prolonged during apneas with face immersion. The results of this study suggest an oxygen-conserving effect of the diving response in trained apneic divers

  • 18. Andersson, Johan
    et al.
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Effects of lung volume and involuntary breathing movements on the human diving response1997In: European Journal of Applied Physiology, ISSN 1439-6319, Vol. 77, no 1/2, p. 19-24Article in journal (Refereed)
    Abstract [en]

    The effects of lung volume and involuntary breathing movements on the human diving response were studied in 17 breath-hold divers. Each subject performed maximal effort apnoeas and simulated dives by apnoea and cold water face immersion, at lung volumes of 60%, 85%, and 100% of prone vital capacity (VC). Time of apnoea, blood pressure, heart rate, skin capillary blood flow, and fractions of end-expiratory CO 2 and O 2 were measured. The length of the simulated dives was the shortest at 60% of VC, probably because at this level the build up of alveolar CO 2 was fastest. Apnoeas with face immersion at 100% of VC gave a marked drop in arterial pressure during the initial 20?s, probably due to high intrathoracic pressure mechanically reducing venous return. The diving response was most pronounced at 60% of VC. We concluded that at the two larger lung volumes both mechanical factors and input from pulmonary stretch receptors influenced the bradycardia and vasoconstriction, resulting in a non-linear relationship between the breath-hold lung volume and magnitude of the diving response in the near-VC range. Furthermore, the involuntary breathing movements that appeared during the struggle phase of the apnoeas were too small to affect the diving response

  • 19. Andersson, Johan
    et al.
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Gislén, Anna
    Holm, Boris
    Cardiovascular responses to cold water immersions of the forearm and face, and their relationship to apnoea2000In: European Journal of Applied Physiology, ISSN 1439-6319, Vol. 83, no 6, p. 566-572Article in journal (Refereed)
    Abstract [en]

    Apnoea as well as cold stimulation of the face or the extremities elicits marked cardiovascular reflexes in humans. The purpose of this study was to investigate whether forearm immersion in cold water has any effect on the cardiovascular responses to face immersion and apnoea. We recorded cardiovascular responses to cold-water immersions of the forearm and face in 19 (part I) and 23 subjects (part II). The experimental protocol was divided in two parts, each part containing four tests: I1, forearm immersion during eupnoea; I2, face immersion during eupnoea; I3, forearm and face immersion during eupnoea; I4, face immersion during apnoea; II1, apnoea without immersion; II2, forearm immersion during apnoea; II3, face immersion during apnoea; and II4, forearm and face immersion during apnoea. The water temperature was 9–11 °C. Cold-water immersion of either the forearm or face was enough to elicit the most pronounced thermoregulatory vasoconstriction during both eupnoea and apnoea. During eupnoea, heart rate responses to forearm immersion (3% increase) and face immersion (9% decrease) were additive during concurrent stimulation (3% decrease). During apnoea, the heart rate responses were not affected by the forearm immersion. The oxygen-conserving diving response seems to dominate over thermoregulatory responses in the threat of asphyxia. During breathing, however, the diving response serves no purpose and does not set thermoregulatory adjustments aside

  • 20.
    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

     

  • 21.
    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.

  • 22.
    Bakker, Emily
    et al.
    Norwegian Univ Sci & Technol, N-7034 Trondheim, Norway.
    Engan, Harald
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering.
    Patrician, Alexander
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering.
    Schagatay, Erika
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Karlsen, Trine
    Norwegian Univ Sci & Technol, N-7034 Trondheim, Norway.
    Wisloff, Ulrik
    Norwegian Univ Sci & Technol, N-7034 Trondheim, Norway.
    Gaustad, Svein Erik
    Norwegian Univ Sci & Technol, N-7034 Trondheim, Norway.
    Effects Of Dietary Nitrate Supplementation On Endothelial Function At High Altitude2014In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 46, no 5, p. 424-424Article in journal (Other academic)
  • 23.
    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.

  • 24. Björkhagen, M
    et al.
    Björkhagen, A
    Engan, Harald
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering.
    Schagatay, Erika
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Role of group dynamics and leadership in the development of acute mountain sickness2014Conference paper (Refereed)
  • 25.
    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.

  • 26. 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.

  • 27.
    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.

  • 28.
    Cotter, Joshua A.
    et al.
    Univ Calif Irvine, Irvine, CA USA .
    Hoang, Theresa
    Univ Calif Irvine, Irvine, CA USA .
    Yu, Alvin
    Univ Calif Irvine, Irvine, CA USA .
    Tesch, Per
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Caiozzo, Vincent J.
    Univ Calif Irvine, Irvine, CA USA .
    Adams, Gregory R.
    Univ Calif Irvine, Irvine, CA USA .
    Counteracting Decrements in Muscle Function and Aerobic Capacity During Unloading Utilizing a Gravity Independent Device2012In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 44, no Suppl 2, p. 110-110Article in journal (Other academic)
  • 29.
    Cotter, Joshua Allan
    et al.
    Univ Calif Irvine, Irvine, CA USA .
    Haddad, Fadia
    Univ Calif Irvine, Irvine, CA USA .
    Yu, Alvin M.
    Univ Calif Irvine, Irvine, CA USA .
    Hoang, Theresa N.
    Univ Calif Irvine, Irvine, CA USA .
    Kreitenberg, Arthur
    Univ Calif Irvine, Irvine, CA USA .
    Baker, Michael J.
    Univ Calif Irvine, Irvine, CA USA .
    Tesch, Per A.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Baldwin, Kenneth M.
    Univ Calif Irvine, Irvine, CA USA .
    Caiozzo, Vincent J.
    Univ Calif Irvine, Irvine, CA USA .
    Adams, Gregory R.
    Univ Calif Irvine, Irvine, CA USA .
    Influence of 10 days of unilateral lower limb suspension and combined exercise training on human vastus lateralis and soleus muscles2012In: The FASEB Journal, ISSN 0892-6638, E-ISSN 1530-6860, Vol. 26Article in journal (Other academic)
  • 30.
    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.
    Milling, U
    Lemon, H
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Erythropoietin production as a result of repeated apneas2004Conference paper (Refereed)
    Abstract [en]

    Background: It has been known for decades that high altitude hypoxia will lead to increased erythropoiesis. Hypoxia in mainly the kidney results in an increased production of erythropoietin (EPO) stimulating erythropoiesis. High altitude natives display a higher haemoglobin concentration than sea level residents, which in turn increase their haemoglobin concentration as part of the adaptation to altitude. Another group of humans exposed to hypoxia is apneic divers, which may endure transient acute hypoxia, spaced by periods of normal breathing. We recently found higher haemoglobin levels in elite apneic divers, compared to groups of elite skiers and untrained subjects, suggesting that apnea training may induce erythropoiesis in humans. It is well known that diving mammals display high haemoglobin concentrations, and the beneficial effects are obvious: A larger oxygen store before diving prolongs the aerobic dive limit, and a higher haemoglobin concentration may speed up recovery after apneas and act as a buffer against acidosis during the dive. Although our group comparisons reveal a higher haemoglobin concentration in divers, it cannot be determined whether this is a training effect or genetically determined i.e. if individuals with higher concentrations of haemoglobin are more prone to take up apneic diving. Methods: To investigate if apnea training can induce EPO production, 5 previously untrained volunteers (3 men and 2 women, mean ageSD 28 5.5 years) performed 15 maximal apneas in a horizontal position in air. The apneas were grouped in 3 series of 5 apneas and spaced by 2 minutes of which 1 minute was spent slightly hyperventilating, to produce apneas sufficiently long to induce hypoxia. Series were spaced by 10 minutes resting periods. To determine EPO levels, venous blood samples were taken before apneas and directly after the last apnea series, followed by samples 1, 2, 3 and 5 hours after the apneas. Results: Mean baseline EPO before the apneas was 10.2 U/L. In all subjects EPO levels increased during the 5 hours period after the apneas. The time for EPO-peak values were different among individuals. The mean peak value occurred after 3 h, where the mean increase was 12 % of the pre apnea reference value. Conclusion: The results suggest that apnea induced intermittent hypoxia could lead to increased erythropoiesis. The evaluation of these findings in a larger group of subjects, including measurements of the individual circadian variations in EPO production, is in progress.

  • 31.
    Ekstam, Marcus
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Söderberg, Daniel
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Fysiskt arbete på simulerad hög höjd motsvarande 3500 m.ö.h Effekter på mjältesvolym och hemoglobin2011Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [sv]

    En mjälteskontraktion vid fysiskt arbete samt hög höjd, resulterar i en frisättning av lagrade röda blodkroppar. Mekanismerna bakom kontraktionen är inte helt kartlagda, men hypoxi är troligtvis en viktig faktor. Syftet med studien var att undersöka mjältens funktion i vila och under fysiskt arbete vid hypoxi. Sju män och sju kvinnor med ålder (medelvärde ± SD) 25,1 (±3,3) år deltog i studien. Försökspersonerna vilade sittandes 20 minuter i normoxi, sedan sittandes 20 minuter i simulerad hypoxi motsvarande 3500 m ö.h. Därefter utfördes ett cykelarbete på en individuellt fastställd belastning i hypoxi, följt av 20 minuters vila sittandes i hypoxi, följt av normoxi. Resultatet visade en minskning i mjältesvolym mellan vila i normoxi och vila i hypoxi med 22,4 %, en ytterligare minskning med 32,5 % vid cykelarbetet, samtidigt som en ökning av Hb kunde ses med 4,9 %. Efter 20 minuters vila hade mjältesvolym och Hb återgått till referensnivån. Slutsatsen är att mjälten kontraherar ytterligare vid fysiskt arbete på simulerad höjd jämfört med kontraktionen vid enbart höjdsimulering, vilket korrelerar med en Hb ökning. Kontraktionen var reversibel och upphörde efter avslutat arbete. Resultaten tyder på att effekten är särskilt uttalad vid fysiskt arbete på hög höjd, vilket är ett nytt fynd.

  • 32.
    Engan, Harald K.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering.
    Cardiovascular, hematological and dietary means to cope with environmentally induced hypoxia in humans2015Doctoral thesis, comprehensive summary (Other academic)
  • 33.
    Engan, Harald K.
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering. LHL Health Röros, Norwegian Heart and Lung Patient Organization, Oslo, Norway.
    Lodin-Sundström, Angelica
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering.
    Schagatay, Fanny
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering.
    Schagatay, Erika
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    The effect of climbing mount everest on spleen contraction and increase in hemoglobin concentration during breath holding and exercise2014In: High Altitude Medicine & Biology, ISSN 1527-0297, E-ISSN 1557-8682, Vol. 15, no 1, p. 52-57Article in journal (Refereed)
    Abstract [en]

    Release of stored red blood cells resulting from spleen contraction improves human performance in various hypoxic situations. This study determined spleen volume resulting from two contraction-evoking stimuli: breath holding and exercise before and after altitude acclimatization during a Mount Everest ascent (8848m). Eight climbers performed the following protocol before and after the climb: 5min ambient air respiration at 1370m during rest, 20min oxygen respiration, 20min ambient air respiration at 1370m, three maximal-effort breath holds spaced by 2min, 10min ambient air respiration, 5min of cycling at 100 W, and finally 10min ambient air respiration. We measured spleen volume by ultrasound and capillary hemoglobin (HB) concentration after each exposure, and heart rate (HR) and arterial oxygen saturation (Sao2) continuously. Mean (SD) baseline spleen volume was unchanged at 213 (101) mL before and 206 (52) mL after the climb. Before the climb, spleen volume was reduced to 184 (83) mL after three breath holds, and after the climb three breath holds resulted in a spleen volume of 132 (26) mL (p=0.032). After exercise, the preclimb spleen volume was 186 (89) mL vs. 112 (389) mL) after the climb (p=0.003). Breath hold duration and cardiovascular responses were unchanged after the climb. We concluded that spleen contraction may be enhanced by altitude acclimatization, probably reflecting both the acclimatization to chronic hypoxic exposure and acute hypoxia during physical work. © Copyright 2014, Mary Ann Liebert, Inc. 2014.

  • 34.
    Engan, Harald
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering.
    Lodin-Sundström, Angelica
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering.
    Schagatay, Fanny
    Schagatay, Erika
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Enhanced blood boosting spleen contraction after climbing Mt Everest2014Conference paper (Refereed)
  • 35.
    Engan, Harald
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering.
    Mattiason, S
    Norwegian Univ Sci & Technol, Trondheim, Norway..
    Bakker, Emily
    Norwegian Univ Sci & Technol, Trondheim, Norway..
    Patrician, Alexander
    Schagatay, Erika
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Effect of dietary nitrate supplementation on blood pressure in native lowlanders at altitude2014Conference paper (Refereed)
  • 36.
    Engan, Harald
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering. Norwegian Heart & Lung Patient Org, LHL Klinikkene Roros, Roros, Norway.
    Schagatay, Erika
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    "Spleen Contraction and Hemoconcentration" Regarding the Review "Hemoconcentration and Hemostasis During Acute Stress: Interacting and Independent Effects" by Austin et al. 20112015In: Annals of Behavioral Medicine, ISSN 0883-6612, E-ISSN 1532-4796, Vol. 49, no 4, p. 634-635Article in journal (Refereed)
  • 37.
    Engan, Harald
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering. Department of Human Movement Science, Faculty of Social Sciences and Technology Management, NTNU, Trondheim, Norway.
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering.
    Lodin-Sundström, Angelica
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering.
    Richardson, Matt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering.
    Beekvelt, Mireille
    Department of Human Movement Science, Faculty of Social Sciences and Technology Management, NTNU, Trondheim, Norway.
    Effects of two weeks of daily apnea training on diving response, spleen contraction, and erythropoiesis in novel subjects.2013In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 23, no 3, p. 340-348Article in journal (Refereed)
    Abstract [en]

    Three potentially protective responses to hypoxia have been reported to be enhanced in divers: (1) the diving response, (2) the blood-boosting spleen contraction, and (3) a long-term enhancement of hemoglobin concentration (Hb). Longitudinal studies, however, have been lacking except concerning the diving response. Ten untrained subjects followed a 2-week training program with 10 maximal effort apneas per day, with pre- and posttraining measurements during three maximal duration apneas, and an additional post-training series when the apneic duration was kept identical to that before training. Cardiorespiratory parameters and venous blood samples were collected across tests, and spleen diameters were measured via ultrasound imaging. Maximal apneic duration increased by 44 s (P < 0.05). Diving bradycardia developed 3 s earlier and was more pronounced after training (P < 0.05). Spleen contraction during apneas was similar during all tests. The arterial hemoglobin desaturation (SaO(2)) nadir after apnea was 84% pretraining and 89% after the duration-mimicked apneas post-training (P < 0.05), while it was 72% (P < 0.05) after maximal apneas post-training. Baseline Hb remained unchanged after training, but reticulocyte count increased by 15% (P < 0.05). We concluded that the attenuated SaO(2) decrease during mimic apneas was due mainly to the earlier and more pronounced diving bradycardia, as no enhancement of spleen contraction or Hb had occurred. Increased reticulocyte count suggests augmented erythropoiesis.

  • 38. Faiss, R
    et al.
    Cheng, AJ
    Karolinska Institute.
    Willis, Sara
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Zinner, Christoph
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Ivarsson, N
    Karolinska Institutet.
    Chaillou, T
    Karolinska Institutet.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Westerblad, H
    Karolinska Institutet.
    Elevated Temperature Accelerates Recovery of Mouse and Human Skeletal Muscle Following Fatigue2015In: Abstract Book for the 20th Annual ECSS Congress, 2015Conference paper (Refereed)
    Abstract [en]

    Introduction

    This study was designed to determine whether elevated muscle temperature allows muscles to recover their force or power more rapidly following fatigue

    Methods

    Intact single fibers from mouse flexor digitorum brevis muscle were fatigued at 31˚C (70-Hz 350-ms tetani once every 10s until initial force decreased to 30%).  During a subsequent 2-hr recovery period, the fibers were perfused in Tyrode solution at either 31°C (physiological temperature) or 36°C and isometric force and cytoplasmic free [Ca2+] ([Ca2+]i) were measured during 30-Hz tetani evoked periodically.  In addition, seven human subjects performed fatiguing arm exercise consisting of 3 x 5min maximal effort arm cycling at 100 rpm followed by 4 x 15 min at an intensity of 50% of VO2peak. Then followed 2hr of recovery during which both arms were either heated or not heated at 5˚C above physiological temperatures using arm cuffs continuously perfused with temperature-regulated water; the order of heating vs. not heating was randomized between two visits. Intramuscular temperature was recorded with probes inserted 1.5 cm into the lateral head of the triceps brachii muscle. During the recovery period, subjects consumed 1.0 g/hr/kg body weight carbohydrates to support glycogen repletion. After recovery, the subjects repeated the 3 x 5 min time trials to evaluate the effect of the recovery intervention.

    Results

    Recovery from fatigue in mouse single fibers was dependent on muscle glycogen restoration since fibers perfused with glucose-free Tyrode did not recover contractile force (P<0.05). After 30 min of recovery, the tetanic [Ca2+]i was 107±10% and 92 ± 8% and the corresponding forces were 69±15% vs.49±14% of the initial values for the heated and non-heated muscles, respectively.  In seven human subjects, 2h of muscle heating also appeared to improve muscle recovery, leading to higher mean power output in the post-recovery arm cycling time trial than without muscle heating.

    Discussion

    Elevating muscle temperature by 5°C above physiological temperature accelerates recovery in mouse muscle in-vitro and in human skeletal muscle in-vivo and this appears to depend on faster muscle glycogen resynthesis following fatigue.

  • 39.
    Fluck, Martin
    et al.
    Univ Zurich, Balgrist Univ Hosp, CH-8006 Zurich, Switzerland.
    Li, Ruowei
    Manchester Metropolitan Univ, Inst Biomed Res Human Movement & Hlth, Manchester M15 6BH, Lancs, England.
    Valdivieso, Paola
    Univ Zurich, Balgrist Univ Hosp, CH-8006 Zurich, Switzerland.
    Linnehan, Richard M.
    Johnson Space Ctr, Natl Aeronaut & Space Adm, Houston, TX USA.
    Castells, Josiane
    Univ St Etienne, Fac Med, EA4338, Lab Physiol Exercice, St Etienne, France.
    Tesch, Per
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Karolinska Inst, Dept Physiol & Pharmacol, Stockholm, Sweden.
    Gustafsson, Thomas
    Karolinska Univ Hosp, Clin Physiol Karolinska Inst, Dept Lab Med, Stockholm, Sweden.
    Early Changes in Costameric and Mitochondrial Protein Expression with Unloading Are Muscle Specific2014In: BioMed Research International, ISSN 2314-6133, E-ISSN 2314-6141, article id 519310Article in journal (Refereed)
    Abstract [en]

    We hypothesised that load-sensitive expression of costameric proteins, which hold the sarcomere in place and position the mitochondria, contributes to the early adaptations of antigravity muscle to unloading and would depend on muscle fibre composition and chymotrypsin activity of the proteasome. Biopsies were obtained from vastus lateralis (VL) and soleus (SOL) muscles of eight men before and after 3 days of unilateral lower limb suspension (ULLS) and subjected to fibre typing and measures for costameric (FAK and FRNK), mitochondrial (NDUFA9, SDHA, UQCRC1, UCP3, and ATP5A1), and MHCI protein and RNA content. Mean cross-sectional area (MCSA) of types I and II muscle fibres in VL and type I fibres in SOL demonstrated a trend for a reduction after ULLS (0.05 <= P < 0.10). FAK phosphorylation at tyrosine 397 showed a 20% reduction in VL muscle (P = 0.029). SOL muscle demonstrated a specific reduction in UCP3 content (-23%; P = 0.012). Muscle-specific effects of ULLS were identified for linear relationships between measured proteins, chymotrypsin activity and fibre MCSA. The molecular modifications in costamere turnover and energy homoeostasis identify that aspects of atrophy and fibre transformation are detectable at the protein level in weight-bearing muscles within 3 days of unloading.

  • 40.
    Hanstock, Helen
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Bangor University, Gwynedd, UK.
    Edwards, Jason
    Bangor University, Gwynedd, UK.
    Roberts, Ross
    Bangor University, Gwynedd, UK.
    Walsh, Neil
    Bangor University, Gwynedd, UK.
    High heart rate reactors display greater decreases in tear SIgA concentration following a novel acute stressor2018In: Biological Psychology, ISSN 0301-0511, E-ISSN 1873-6246, Vol. 133, p. 85-88Article in journal (Refereed)
    Abstract [en]

    Tear secretory immunoglobulin-A (SIgA) is a putative biomarker of common-cold risk with potential utility in non-invasive diagnostics. As SIgA secretion at the ocular surface is under strong autonomic control, we investigated the relationship between HR reactivity and tear SIgA responses to novel experiential stress. Thirty-two healthy participants undertook a 60-second zip-line ride to evoke acute stress and a seated-rest control trial in a randomised-crossover design. We recorded heart rate (HR) continuously and collected unstimulated tear samples 5-min-pre-, 2-min-post- and 20-min-post-stress/control. Stress increased HR and state anxiety whereas tear SIgA concentration decreased 44% post-stress vs. control. Higher peak HR values during stress uniquely explained 21% of the variance in tear SIgA reactivity to stress (p < .01); high HR reactors displayed greater decreases in tear SIgA concentration. We conclude that physiological arousal increases immune reactivity to acute stress and highlight tear SIgA as a minimally-invasive, physiologically relevant biomarker of immune reactivity.

  • 41. Holm, Boris
    et al.
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, Johan
    A possible physiological role of the face as a thermosensor in an ancient water ape and in present day man1999In: Perspectives in Human Biology, Vol. 4, p. 41-46Article in journal (Refereed)
  • 42. Holm, Boris
    et al.
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Kobayashi, Toshio
    Masuda, Atsuko
    Ohdaira, Tetsuro
    Honda, Yoshiyuki
    Cardiovascular Change in Elderly Male Breath-hold Divers (Ama) and their Socio-economical Background at Chikura in Japan.1998In: Applied Human Science;Journal of Physiological Anthropology, ISSN 1341-3473, Vol. 17, no 5, p. 181-187Article in journal (Refereed)
    Abstract [en]

    The Ama have existed for more than 2000 years in Japan and Korea. They have been diving for seaweed and molluscs. Their traditional way of fishing, with goggles or a mask, but without a wetsuit, is still practised as a result of laws against overfishing. We investigated cardiovascular diving responses, expressed as heart rate (HR) reduction, peripheral vasoconstriction indicated by skin blood flow (SkBF) and mean arterial blood pressure (MAP) during breath-hold face immersion in a group of eight elderly male Ama at Chikura, Japan. Their data were compared to those from three other groups: a) elderly non-divers; b) young divers and c) young non-divers. Our previous studies have shown that young divers show a more pronounced bradycardia than young non-divers. The present study of elderly Ama and elderly non-divers was performed to investigate if this difference persists in old age. We found that, in spite of many years of diving experience, HR reduction of the elderly professional divers observed during face immersion did not differ from that of elderly non-divers, but it was much less pronounced than in the two younger groups. We conclude that even if a well-developed diving response at young age has been reduced to the level of non-divers, the Ama are still able to continue their work of diving in old age. Ama that has been a traditionally female occupation, is mostly practised by men at Chikura today. No young have been recruited for this profession. Therefore, the present Ama are senior and the traditional breath-hold diving will probably cease to exist in the near future. The probable reasons for these changes are discussed

  • 43.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    The competitive cross-country skier - an impressive human engine.2009In: Science and Skiing IV, Maidenhead: Meyer & Meyer Sport, 2009, p. 101-109Chapter in book (Other academic)
    Abstract [en]

    Cross-country skiing is one of the most demanding endurance sports. It imposes extensive physiological challenges due to the perpetual changes between, and utilisation of, different skiing techniques, each involving the upper and lower body to various extents. Altogether, the uniqueness of the sport has over the years contributed to significant interest from physiologists in their ongoing ambition to understand more about the human engine.

  • 44.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    The elite cross-country skier provides unique insights into human exercise physiology2015In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 25, no S4, p. 100-109Article, review/survey (Refereed)
    Abstract [en]

    Successful cross-country skiing, one of the most demanding of endurance sports, involves considerable physiological challenges posed by the combined upper- and lower-body effort of varying intensity and duration, on hilly terrain, often at moderate altitude and in a cold environment. Over the years, this unique sport has helped physiologists gain novel insights into the limits of human performance and regulatory capacity. There is a long-standing tradition of researchers in this field working together with coaches and athletes to improve training routines, monitor progress, and refine skiing techniques. This review summarizes research on elite cross-country skiers, with special emphasis on the studies initiated by Professor Bengt Saltin. He often employed exercise as a means to learn more about the human body, successfully engaging elite endurance athletes to improve our understanding of the demands, characteristics, and specific effects associated with different types of exercise.

  • 45.
    Holmberg, Hans-Christer
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Bonne, Thomas
    Örtenblad, Niels
    Depletion and resynthesis of glycogen in arm and leg muscles after a classical 15-K cross-country ski race2008In: Proceedings of the 13th Annual Congress of the European College of Sports Science, Cologne: Sportools , 2008, p. 660-Conference paper (Refereed)
    Abstract [en]

    Introduction: Bicycle exercise or running has been most frequently used in studies of glycogen usage during exercise and the replenishment in the recovery afterwards. In cross-country skiing muscle glycogen is probably a dominant factor for maintaining speed and can be crucial in the finish. In this sport the arms may be more critical than the legs both for speed and finish, especially in the classical technique. Thus, in the present study we examined muscle glycogen content in arm and leg muscle in connection with a race and the first 24 hrs after the race with two specific aims. 1) Evaluate whether arm muscles use more glycogen than the leg muscles and whether there is a muscle fibre type specific glycogen depletion pattern for the type 2 fibres, 2) Evaluate whether water intake instead for carbohydrates during the first 4 hrs after the race affect the resynthesis of glycogen acutely and next morning. Methods: Ten elite male competitive cross-country skiers (Age:22; Body height:182 cm; Body mass:80.8 kg; VO2max:72 ml kg-1 min-1) performed a 15K classical race in varying terrain. The subjects were placed into two groups; a H2O-group and a CHO-group. Directly after the race the H20-group was only allowed to drink water whereas the CHO-group used a normal post-race strategy to refill CHO with sport drink and gel and thereafter a meal. After 4 hrs both groups had the same carbohydrate enriched food intake. Muscle biopsies were obtained from an arm (triceps brachii) and a leg (v. lateralis) muscle before, directly after, as well as 4 and 20 hrs after the race. Muscles samples were analyzed for fibre types and glycogen as well as glycogen depletion pattern. Results: Muscle glycogen measured directly after the race was reduced by 32 % (484.7 to 331.3 mmol kg-1dw) in the legs and 69 % (from 540.2 to 167.1 mmol kg-1dw) in the arms. Type 1 muscle fibre type depletion was the dominant finding for both arms and legs, with some type 2A fibres being partly depleted in the arms. After 4 hrs with water no elevation in neither arm nor leg muscle glycogen content was observed but with CHO the legs did increase with 80 and the arms with 110 mmol kg-1dw and significantly more in the legs compared to the arms(P<0.05). Next morning regardless of being in H20- or the CHO group all subjects had returned to close to their pre-race muscle glycogen content in both arms and legs. Conclusion: The main findings were 1) in classical/diagonal skiing is the recruitment pattern of muscle fibre types the typical for prolonged exercise with primarily type 1 fibres being glycogen depleted but equally clear is that the arms are more used than the leg muscle as muscle glycogen stores were more markedly utilized in the arm as compared to the leg muscles.2) Restoration of the muscle glycogen stores are dependant of a carbohydrate intake but of note is that in only 20 hrs of recovery was the pre exercise glycogen level reached regardless of no carbohydrate intake for 4 hrs immediately after the race.

  • 46.
    Hostrup, M.
    et al.
    Department of Nutrition, Exercise and Sports, Section of Integrated Physiology, University of Copenhagen, Denmark .
    Kalsen, A.
    Department of Nutrition, Exercise and Sports, Section of Integrated Physiology, University of Copenhagen, Denmark .
    Ørtenblad, Niels
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Department of Sports Science and Biomechanics, University of Southern Denmark, Denmark .
    Juel, C.
    Department of Biology, University of Copenhagen, Denmark .
    Mørch, K.
    Department of Nutrition, Exercise and Sports, Section of Integrated Physiology, University of Copenhagen, Denmark .
    Rzeppa, S.
    Norwegian Doping Control Laboratory, Oslo University Hospital, Norway .
    Karlsson, S.
    Department of Respiratory Research, Bispebjerg University Hospital, Denmark .
    Backer, V.
    Department of Respiratory Research, Bispebjerg University Hospital, Denmark .
    Bangsbo, J.
    Department of Nutrition, Exercise and Sports, Section of Integrated Physiology, University of Copenhagen, Denmark .
    β2-Adrenergic stimulation enhances Ca2+ release and contractile properties of skeletal muscles, and counteracts exercise-induced reductions in Na+-K+-ATPase Vmax in trained men2014In: Journal of Physiology, ISSN 0022-3751, E-ISSN 1469-7793, Vol. 592, no 24, p. 5445-5459Article in journal (Refereed)
    Abstract [en]

    The aim of the present study was to examine the effect of β2-adrenergic stimulation on skeletal muscle contractile properties, sarcoplasmic reticulum (SR) rates of Ca2+ release and uptake, and Na+-K+-ATPase activity before and after fatiguing exercise in trained men. The study consisted of two experiments (EXP1, n = 10 males, EXP2, n = 20 males), where β2-adrenoceptor agonist (terbutaline) or placebo was randomly administered in double-blinded crossover designs. In EXP1, maximal voluntary isometric contraction (MVC) of m. quadriceps was measured, followed by exercise to fatigue at 120% of maximal oxygen uptake (V˙O2, max ). A muscle biopsy was taken after MVC (non-fatigue) and at time of fatigue. In EXP2, contractile properties of m. quadriceps were measured with electrical stimulations before (non-fatigue) and after two fatiguing 45 s sprints. Non-fatigued MVCs were 6 ± 3 and 6 ± 2% higher (P &lt; 0.05) with terbutaline than placebo in EXP1 and EXP2, respectively. Furthermore, peak twitch force was 11 ± 7% higher (P &lt; 0.01) with terbutaline than placebo at non-fatigue. After sprints, MVC declined (P &lt; 0.05) to the same levels with terbutaline as placebo, whereas peak twitch force was lower (P &lt; 0.05) and half-relaxation time was prolonged (P &lt; 0.05) with terbutaline. Rates of SR Ca2+ release and uptake at 400 nm [Ca2+] were 15 ± 5 and 14 ± 5% (P &lt; 0.05) higher, respectively, with terbutaline than placebo at non-fatigue, but declined (P &lt; 0.05) to similar levels at time of fatigue. Na+-K+-ATPase activity was unaffected by terbutaline compared with placebo at non-fatigue, but terbutaline counteracted exercise-induced reductions in maximum rate of activity (Vmax) at time of fatigue. In conclusion, increased contractile force induced by β2-adrenergic stimulation is associated with enhanced rate of Ca2+ release in humans. While β2-adrenergic stimulation elicits positive inotropic and lusitropic effects on non-fatigued m. quadriceps, these effects are blunted when muscles fatigue.

  • 47.
    Hostrup, Morten
    et al.
    Univ Copenhagen, Dept Nutr Exercise & Sports, Sect Integrated Physiol, DK-2100 Copenhagen, Denmark.;Bispebjerg Hosp, Dept Resp Res, Copenhagen, Denmark..
    Kalsen, Anders
    Univ Copenhagen, Dept Nutr Exercise & Sports, Sect Integrated Physiol, DK-2100 Copenhagen, Denmark.;Bispebjerg Hosp, Dept Resp Res, Copenhagen, Denmark..
    Onslev, Johan
    Univ Copenhagen, Dept Nutr Exercise & Sports, Sect Integrated Physiol, DK-2100 Copenhagen, Denmark.;Bispebjerg Hosp, Dept Resp Res, Copenhagen, Denmark..
    Jessen, Soren
    Univ Copenhagen, Dept Nutr Exercise & Sports, Sect Integrated Physiol, DK-2100 Copenhagen, Denmark.;Bispebjerg Hosp, Dept Resp Res, Copenhagen, Denmark..
    Haase, Christoffer
    Bispebjerg Hosp, Dept Resp Res, Copenhagen, Denmark..
    Habib, Sajad
    Univ Copenhagen, Dept Nutr Exercise & Sports, Sect Integrated Physiol, DK-2100 Copenhagen, Denmark..
    Örtenblad, Niels
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Univ Southern Denmark, Dept Sports Sci & Biomech, Odense, Denmark.;Mid Sweden Univ, Swedish Winter Sports Res Ctr, Sundsvall, Sweden..
    Backer, Vibeke
    Bispebjerg Hosp, Dept Resp Res, Copenhagen, Denmark..
    Bangsbo, Jens
    Univ Copenhagen, Dept Nutr Exercise & Sports, Sect Integrated Physiol, DK-2100 Copenhagen, Denmark..
    Mechanisms underlying enhancements in muscle force and power output during maximal cycle ergometer exercise induced by chronic beta(2)-adrenergic stimulation in men2015In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 119, no 5, p. 475-486Article in journal (Refereed)
    Abstract [en]

    The study was a randomized placebo-controlled trial investigating mechanisms by which chronic beta(2)-adrenergic stimulation enhances muscle force and power output during maximal cycle ergometer exercise in young men. Eighteen trained men were assigned to an experimental group [oral terbutaline 5 mg/30 kg body weight (bw) twice daily (TER); n = 9] or a control group [placebo (PLA); n = 9] for a 4-wk intervention. No changes were observed with the intervention in PLA. Isometric muscle force of the quadriceps increased (P <= 0.01) by 97 +/- 29 N (means +/- SE) with the intervention in TER compared with PLA. Peak and mean power output during 30 s of maximal cycling increased (P <= 0.01) by 32 +/- 8 and 25 +/- 9 W, respectively, with the intervention in TER compared with PLA. Maximal oxygen consumption ((V) over dotO(2)max) and time to fatigue during incremental cycling did not change with the intervention. Lean body mass increased by 1.95 +/- 0.8 kg (P <= 0.05) with the intervention in TER compared with PLA. Change in single fiber cross-sectional area of myosin heavy chain (MHC) I (1,205 +/- 558 mu m(2); P <= 0.01) and MHC II fibers (1,277 +/- 595 mu m(2); P <= 0.05) of the vastus lateralis muscle was higher for TER than PLA with the intervention, whereas no changes were observed in MHC isoform distribution. Expression of muscle proteins involved in growth, ion handling, lactate production, and clearance increased (P <= 0.05) with the intervention in TER compared with PLA, with no change in oxidative enzymes. Our observations suggest that muscle hypertrophy is the primary mechanism underlying enhancements in muscle force and peak power during maximal cycling induced by chronic beta(2-)adrenergic stimulation in humans.

  • 48.
    Johansson, O
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering.
    Patrician, Alexander
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering.
    Wisniewski, Sarah
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering.
    Schagatay, Erika
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Spirometry during ascent to altitude and its correlation to acute mountain sickness2014Conference paper (Refereed)
    Abstract [en]

    Easily measurable variables capable of predicting altitude sickness, before symptom onset, would be beneficial for those requiring slower ascent or even medical attention. Unfortunately few such reliable factors exist. Our objective was to test respiratory function during ascent in the Nepali Himalaya, to see if any correlations with altitude sickness, expressed by Lake Louis scores, could be identified. Eleven healthy subjects (six male and five female, mean(SD) age 26(9.3) years) travelled from 1370m to 4200m, and spent 9 days at or above this altitude. Variables of lung function, including vital capacity, forced expiratory volume over one second (FEV1) and peak expiratory flow were measured using a portable spirometer every-other morning before breakfast in the standing position. Subjects also completed the Lake Louis self-assessment questionnaire daily. Mean(SD) vital capacity and FEV1 decreased from 5.3(1.4) L and 4.5(0.9) L at 1370m to 4.8(1.4) L and 4.2(1.0) L at 4200m, respectively (p<0.05), but did not correlate to Lake Louis scores. Mean(SD) peak expiratory flow was 9.4(2.3) L/s at 1370m and did not change during ascent. However once at 4200m it increased from 9.2(2.7) L/s to 9.6(2.4) L/s following the stay at altitude (p<0.05). Interestingly, an absolute change in peak expiratory flow at 4200m compared to 1370m, showed a high correlation to Lake Louis scores at 3700m and 4200m (r= -0.971; p<0.001). We conclude that peak expiratory flow values were closely related to signs of altitude sickness, and should be explored further for determining their predictive value.

  • 49.
    Johansson, Orio
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Lung-packing and stretching increases vital capacity in recreational freedivers2012In: The European respiratory journal. Supplement, ISSN 0904-1850, Vol. 40, no Supplement 56, p. 149s-Article in journal (Refereed)
  • 50.
    Kehler, Alyse
    et al.
    Univ Colorado, Dept Integrat Physiol, Boulder, CO 80309 USA.
    Hajkova, E
    Univ Colorado, Dept Integrat Physiol, Boulder, CO 80309 USA.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Kram, Rodger
    Univ Colorado, Dept Integrat Physiol, Boulder, CO 80309 USA.
    Forces and mechanical energy fluctuations during diagonal stride roller skiing; running on wheels?2014In: Journal of Experimental Biology, ISSN 0022-0949, E-ISSN 1477-9145, Vol. 217, no 21, p. 3779-3785Article in journal (Refereed)
    Abstract [en]

    Mechanical energy can be conserved during terrestrial locomotion in two ways: the inverted pendulum mechanism for walking and the spring-mass mechanism for running. Here, we investigated whether diagonal stride cross-country roller skiing (DIA) utilizes similar mechanisms. Based on previous studies, we hypothesized that running and DIA would share similar phase relationships and magnitudes of kinetic energy (KE), and gravitational potential energy (GPE) fluctuations, indicating elastic energy storage and return, as if roller skiing is like 'running on wheels'. Experienced skiers (N=9) walked and ran at 1.25 and 3 m s(-1), respectively, and roller skied with DIA at both speeds on a level dual-belt treadmill that recorded perpendicular and parallel forces. We calculated the KE and GPE of the center of mass from the force recordings. As expected, the KE and GPE fluctuated with an out-of-phase pattern during walking and an in-phase pattern during running. Unlike walking, during DIA, the KE and GPE fluctuations were in phase, as they are in running. However, during the glide phase, KE was dissipated as frictional heat and could not be stored elastically in the tendons, as in running. Elastic energy storage and return epitomize running and thus we reject our hypothesis. Diagonal stride cross-country skiing is a biomechanically unique movement that only superficially resembles walking or running.

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