Physiological demands of competitive elite cross-country skiing

Introduction Researchers have, for decades, contributed to an increased collective understanding of the physiological demands in cross-country skiing; however, almost all of these studies have used either non-elite subjects and/or performances that emulate cross-country skiing. To establish the physiological demands of cross-country skiing, it is important to relate the investigated physiological variables to the competitive performance of elite skiers. The overall aim of this doctoral thesis was, therefore, to investigate the external validity of physiological test variables to determine the physiological demands in competitive elite cross-country skiing. Methods The subjects in Study I – IV were elite male (I – III) and female (III – IV) cross-country skiers. In all studies, the relationship between test variables (general and ski-specific) and competitive performances (i.e. the results from competitions or the overall ski-ranking points of the International Ski Federation (FIS) for sprint (FISsprint) and distance (FISdist) races) were analysed. Test variables reflecting the subject’s general strength, upper-body and whole-body oxygen uptake, oxygen uptake and work intensity at the lactate threshold, mean upper-body power, lean mass, and maximal double-poling speed were investigated. Results The ability to maintain a high work rate without accumulating lactate is an indicator of distance performance, independent of sex (I, IV). Independent of sex, high oxygen uptake in whole-body and upper-body exercise was important for both sprint (II, IV) and distance (I, IV) performance. The maximal double-poling speed and 60-s double-poling mean power output were indicators of sprint (IV) and distance performance (I), respectively. Lean mass was correlated with distance performance for women (III), whereas correlations were found between lean mass and sprint performance among both male and female skiers (III). Moreover, no correlations between distance performance and test variables were derived from tests of knee-extension peak torque, vertical jumps, or double poling on a ski-ergometer with 20-s and 360-s durations (I), whereas gross efficiency while treadmill roller skiing showed no correlation with either distance or sprint performance in cross-country skiing (IV). Conclusion The results in this thesis show that, depending on discipline and sex, maximal and peak oxygen uptake, work intensity at the lactate threshold, lean mass, double-poling mean power output, and double-poling maximal speed are all externally valid physiological test variables for evaluation of performance capability among elite cross-country skiers; however, to optimally indicate performance capability different test-variable expressions should be used; in general, the absolute expression appears to be a better indicator of competitive sprint performance whereas the influence of body mass should be considered when evaluating competitive distance performance capability of elite cross-country skiers.

Aerobic and anaerobic test performance among elite male football players in different team positions

The purpose was to determine the magnitude of aerobic and anaerobic performance factors among elite male football players in different team positions. Thirty-nine players from the highest Swedish division classified as defenders (n=18), midfield players (n=12) or attackers (n=9) participated. Their mean (± sd) age, height and body mass (bm) were 24.4 (±4.7) years, 1.80 (±5.9)m and 79 (±7.6)kg, respectively. Running economy (RE) and anaerobic threshold (AT) was determined at 10, 12, 14, and 16km/h followed by tests of maximal oxygen uptake (VO2max). Maximal strength (1RM) and average power output (AP) was performed in squat lifting. Squat jump (SJ), counter-movement jump with free arm swing (CMJa), 45m maximal sprint and the Wingate test was performed. Average VO2max for the whole population (WP) was 57.0mL O2•kg-1min-1 . The average AT occurred at about 84% of VO2max. 1RM per kg bm0.67 was 11.9±1.3kg. Average squat power in the whole population at 40% 1RM was 70±9.5W per kg bm0.67 . SJ and CMJa were 38.6±3.8cm and 48.9±4.4cm, respectively. The average sprint time (45m) was 5.78± 0.16s. The AP in the Wingate test was 10.6±0.9W•kg-1 . The average maximal oxygen uptake among players in the highest Swedish division was lower compared to international elite players but the Swedish players were better off concerning the anaerobic threshold and in the anaerobic tests. No significant differences were revealed between defenders, midfielders or attackers concerning the tested parameters presented above.

Aerobic and anaerobic test performance among elite male football players in different team positions

The purpose was to determine the magnitude of aerobic and anaerobic performance factors among elite male football players in different team positions. Thirty-nine players from the highest Swedish division classified as defenders (n=18), midfield players (n=12) or attackers (n=9) participated. Their mean (± sd) age, height and body mass (bm) were 24.4 (±4.7) years, 1.80 (±5.9)m and 79 (±7.6)kg, respectively. Running economy (RE) and anaerobic threshold (AT) was determined at 10, 12, 14, and 16km/h followed by tests of maximal oxygen uptake (VO2max). Maximal strength (1RM) and average power output (AP) was performed in squat lifting. Squat jump (SJ), counter-movement jump with free arm swing (CMJa), 45m maximal sprint and the Wingate test was performed. Average VO2max for the whole population (WP) was 57.0mL O2•kg-1min-1. The average AT occurred at about 84% of VO2max. 1RM per kg bm0.67 was 11.9±1.3kg. Average squat power in the whole population at 40% 1RM was70±9.5W per kg bm0.67. SJ and CMJa were 38.6±3.8cm and 48.9±4.4cm,respectively. The average sprint time (45m) was 5.78± 0.16s. The AP in the Wingate test was 10.6±0.9W•kg-1. The average maximal oxygen uptake among players in the highest Swedish division was lower compared to international elite players but the Swedish players were better off concerning the anaerobic threshold and in the anaerobic tests. No significant differences were revealed between defenders, midfielders or attackers concerning the tested parameters presented above.

Optimal V. O2max-to-mass ratio for predicting 15 km performance among elite male cross-country skiers

The aim of this study was 1) to validate the 0.5 body-mass exponent for maximal oxygen uptake (V. O2max) as the optimal predictor of performance in a 15 km classical-technique skiing competition among elite male cross-country skiers and 2) to evaluate the influence of distance covered on the body-mass exponent for V. O2max among elite male skiers. Twenty-four elite male skiers (age: 21.4±3.3 years [mean ± standard deviation]) completed an incremental treadmill roller-skiing test to determine their V. O2max. Performance data were collected from a 15 km classicaltechnique cross-country skiing competition performed on a 5 km course. Power-function modeling (ie, an allometric scaling approach) was used to establish the optimal body-mass exponent for V . O2max to predict the skiing performance. The optimal power-function models were found to be race speed = 8.83⋅(V . O2max m-0.53) 0.66 and lap speed = 5.89⋅(V . O2max m-(0.49+0.018lap)) 0.43e0.010age, which explained 69% and 81% of the variance in skiing speed, respectively. All the variables contributed to the models. Based on the validation results, it may be recommended that V. O2max divided by the square root of body mass (mL⋅min−1 ⋅kg−0.5) should be used when elite male skiers’ performance capability in 15 km classical-technique races is evaluated. Moreover, the body-mass exponent for V . O2max was demonstrated to be influenced by the distance covered, indicating that heavier skiers have a more pronounced positive pacing profile (ie, race speed gradually decreasing throughout the race) compared to that of lighter skiers.