| 1. |
- Hegge, A. M., et al.
(författare)
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Gender differences in power production, energetic capacity and efficiency of elite cross-country skiers during whole-body, upper-body, and arm poling
- 2016
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 116:2, s. 291-300
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To characterize gender differences in power output, energetic capacity and exercise efficiency during whole-body (WP), upper-body (UP), and arm poling (AP). Methods: Ten male and ten female elite cross-country skiers, matched for international performance level, completed three incremental submaximal tests and a 3-min self-paced performance test on a Concept2 SkiErg. Power output, cardiorespiratory and kinematic variables were monitored. Body composition was determined by dual-energy X-ray absorptiometry. Results: The men demonstrated 87, 97 and 103 % higher power output, and 51, 65 and 71 % higher VO2peak (L min−1) than the women during WP, UP and AP, respectively, while utilizing ~10 % more of their running VO2max in all modes (all P < 0.001). The men had 35, 38 and 59 % more lean mass in the whole body, upper body and arms (all P < 0.001). The men exhibited greater shoulder and elbow extension at the start of poling and greater trunk flexion at the end of poling (all P < 0.05). The relationship between VO2 and power output did not differ between the men and women. Conclusions: Gender differences in power production and peak aerobic capacity increased sequentially from WP to UP to AP, coinciding with a greater portion of the muscle mass in the arms of the men. Although the men and women employed each poling technique differently, the estimated efficiency of double poling was independent of gender.
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| 2. |
- Kehler, Alyse, et al.
(författare)
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Forces and mechanical energy fluctuations during diagonal stride roller skiing; running on wheels?
- 2014
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 217:21, s. 3779-3785
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Tidskriftsartikel (refereegranskat)abstract
- 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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| 3. |
- Nilsson, Johnny E, et al.
(författare)
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Effects of 20-s and 180-s double poling interval training in cross-country skiers
- 2004
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 92:1/2, s. 121-127
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to investigate the effect of upper body 20-s or 180-s interval training, using a double poling ergometer, on upper body power output and selected physiological and biomechanical parameters in cross-country skiers. Twenty (12 male, 8 female) well-trained cross-country skiers took part. Two intervention groups, a 20-s interval training group (IT20; n=6) and a 180-s interval training group (IT180; n=7), underwent training three times a week for 6 weeks on a double poling ergometer. A third group served as a control (CON; n=7) and followed the same training program as the IT20 and IT180 groups without the double poling ergometer interval training. The IT20 and IT180 groups significantly (P<0.05) increased both peak and mean power in a 30-s test and mean power in a 6-min test after double poling training. There was a significant improvement in work efficiency in both IT20 and IT180 (P<0.05) and, in IT180, a significant reduction (P<0.05) in blood lactate concentration at given sub-maximal workloads. VO(2peak) increased significantly during double poling in IT180 ( P<0.05) only. VO(2max) did not change significantly in either group. There were no significant changes in any of the test variables in CON. In conclusion, this study shows that 6 weeks of 20-s or 180-s double poling interval training, three times a week, significantly increases power output in both 30-s and 6-min tests, as well as in selected physiological and biomechanical parameters in well-trained cross-country skiers.
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| 4. |
- Psilander, Niklas, et al.
(författare)
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Effects of training, detraining, and retraining on strength, hypertrophy, and myonuclear number in human skeletal muscle
- 2019
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Ingår i: Journal of Applied Physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 126:6, s. 1636-1645
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Tidskriftsartikel (refereegranskat)abstract
- Previously trained mouse muscles acquire strength and volume faster than naive muscles; it has been suggested that this is related to increased myonuclear density. The present study aimed to determine whether a previously strength-trained leg (mem-leg) would respond better to a period of strength training than a previously untrained leg (con-leg). Nine men and 10 women performed unilateral strength training (T1) for 10 wk, followed by 20 wk of detraining (DT) and a 5-wk bilateral retraining period (T2). Muscle biopsies were taken before and after each training period and analyzed for myonuclear number, fiber volume, and cross-sectional area (CSA). Ultrasound and one repetition of maximum leg extension were performed to determine muscle thickness (MT) and strength. CSA (similar to 17%), MT (similar to 10%), and strength (similar to 20%) increased during T1 in the mem-leg. However, the myonuclear number and fiber volume did not change. MT and CSA returned to baseline values during DT, but strength remained elevated (similar to 60%), supporting previous findings of a long-lasting motor learning effect. MT and strength increased similarly in the mem-leg and con-leg during T2, whereas CSA, fiber volume, and myonuclear number remained unaffected. In conclusion, training response during T2 did not differ between the mem-leg and con-leg. However, this does not discount the existence of human muscle memory. since no increase in the number of myonuclei was detected during T1 and no clear detraining effect was observed for cell size during DT; thus, the present data did not allow for a rigorous test of the muscle memory hypothesis. NEW & NOTEWORTHY If a long-lasting intramuscular memory exists in humans. this will affect strength-training advice for both athletes and the public. Based on animal experiments, we hypothesized that such a memory exists and that it is related to the myonuclear number. However, a period of unilateral strength training, followed by detraining, did not increase the myonuclear number. The training response, during a subsequent bilateral retraining period, was not enhanced in the previously trained leg.
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| 5. |
- Welde, Boye, et al.
(författare)
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The pacing strategy and technique of male cross-country skiers with different levels of performance during a 15-km classical race
- 2017
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:11
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Tidskriftsartikel (refereegranskat)abstract
- In this study the pacing strategy, cycle characteristics and choice of technique of elite male cross-country (XC) skiers during a three-lap, 15-km classical race with interval start were measured. During the Norwegian Championships in 2016, fast (n = 18, age: 26±4 yr; height: 182±4 cm; body mass: 78±3 kg (means±SD)) and slow skiers (n = 18, age: 22±2 yr; height: 183±5 cm; body mass: 78±6 kg) were video recorded on flat (0), intermediate (3.5) and uphill sections (7.1) of the first and final laps. All skiers adopted a positive pacing strategy, skiing more slowly (11.8%) with shorter cycles (11.7%) on the final than first lap (both p<0.001; pη2 = 0.93 and 0.87, respectively). The fast skiers were 7.0% faster overall (p<0.001, d = 4.20), and 6.1% (p<0.001, d = 3.32) and 7.0% (p<0.001, d = 3.68) faster on the first and final laps, respectively, compared to slower skiers. On all sections of both laps, the fast skiers exhibited 9.5% more rapid (pη2 = 0.74) and 8.9% (pη2 = 0.48) longer cycles (both p<0.001). On intermediate terrain, the fast skiers employed primarily double poling (DP, 38.9% on the first lap) and double poling with a kick (DPKICK, 50% on the final lap). In contrast, the slow skiers utilized for the most part DP alone (lap 1: 33.3%, lap 3: 38.9%) or in combination with other techniques (lap 1: 33.3%, lap 3: 38.9%) and decreased their usage of DPKICK from 27.8% on the first to 16.7% on the final lap. Skiing velocity on flat and intermediate terrain proved to be the best predictor of race performance (p<0.001). In conclusion, during a 15-km classical XC skiing race, velocity and cycle length decreased from the first to the final lap, most extensively on flat terrain and least uphill. Moreover, on the intermediate sections the fast and slow skiers chose to use different techniques.
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