Search

This study focused on resolving the differences in economy between two common sit-skiing postures used by disabled athletes, suspected to be the most and least effective. Ten experienced non-disabled male cross-country skiers went through an incremental testing protocol with an ergometer simulating double poling in two sitting postures “kneeing” and “knee-high.” The protocol consisted of 3 × 4 min steady-state stages (13, 22, and 34% of maximal sprint power output). Subjects' respiratory gases and heart rate were measured and blood lactate concentrations were determined. In addition, pulling forces and motion capture recordings were collected. Oxygen consumption was 15.5% (p < 0.01) higher with “knee-high” compared to “kneeing” at stage three. At stage three cycle rate was 13.8% higher (p < 0.01) and impulse of force 13.0% (p < 0.05) and hip range of motion 46.6% lower (p < 0.01) with “knee-high” compared to “kneeing.” “Kneeing” was found to be considerably more economical than “knee-high” especially at 34% of maximum sprint power output. This might have been due to higher cycle rate, lower impulse of force and smaller hip range of motion with “knee-high” compared to “kneeing.” This indicates that sit-skiers should adopt, if possible, posture more resembling the “kneeing” than the “knee-high” posture. Combining such physiological and biomechanical measurements and to further develop them to integrated miniature wearable sensors could offer new possibilities for training and testing both in the laboratory and in the field conditions. peerReviewed

INTRODUCTION: This study aimed to 1) determine basic physiological demands during a simulated on-snow cross-country skiing (XCS) race when using grip-waxed skis (all classic XCS techniques [CLASSIC]), versus glide-waxed skis for exclusive double poling (DP) and 2) analyze in which track sections DP is different from CLASSIC under controlled gliding conditions in elite junior and senior skiers. METHODS: Nineteen male and female elite XC skiers performed 1) two randomized simulated XCS races over 5.3 km using DP or CLASSIC measuring section times, VO2, HR, blood lactate, and RPE; and 2) VO2peak tests using diagonal stride and DP on treadmill. RESULTS: The total group showed no differences in performance or physiological responses between DP and CLASSIC. Elite male skiers achieved improved (23 s, P < 0.05), male juniors equal (P > 0.05) and females worse (43 s, P < 0.05) performance with DP versus CLASSIC. Flat and undulating terrain favored DP in men, whereas uphill favored CLASSIC in females (60 s). Uphill sections showed the greatest group differences. Greater RPE was found in the arms during DP, whereas RPE was greater in the legs using CLASSIC. VO2peak in DP was 95% of VO2max. CONCLUSIONS: Male skiers demonstrated superior performance with exclusively using DP on a Fédération International de Ski regulation-compliant XCS track, whereas junior males achieved similar, and females' weaker performance using DP versus CLASSIC. The greatest potential in females is in uphill sections where they distinctly lose time. Exclusive DP might only be beneficial in athletes with high upper-body capacity, and double-pole-specific training and technique. To generalize the findings of the current study, further analysis of snow conditions and course topography is required. (VLID)3545319

Increases in physical (e.g., high-intensity running and sprinting), technical (e.g., passing rate), and tactical (e.g., player density) aspects made elite level soccer more challenging within the past years. The aim of the study was to evaluate whether these evolutions are also been reflected in changes in anthropometric and fitness characteristics between former (2002 to 2005) and current (2012 to 2015) elite Austrian youth development center (U13 to U14) and soccer academy (U15 to U18) players. A battery of anthropometric, general and soccer-specific fitness tests was conducted annually at the end of each year. Independent t-test and Cohens d (ES) were calculated to compare the two four-year periods (2530 vs. 2611 players) at each age group separately. Current players were significantly faster in 20 m sprint (ES = 0.260.50) and reaction test (ES = 0.150.39, except for U18), but less flexible at sit-and-reach (ES = 0.19 to 0.55), in all age categories. Whereas height (ES = 0.260.32), body mass (ES = 0.110.18) and countermovement jump (ES = 0.240.26) increased significantly at youth development center level, current academy players performed superior at shuttle sprint (ES = 0.210.59), hurdles agility run (ES = 0.240.49), and endurance run (ES = 0.110.20). These changes over time in speed, change-of-direction ability, lower-body power, coordination, and endurance were attributed to modern training approaches (e.g., modified games and change-of-direction drills) and modifications in selection politics (e.g., coaches favor speed and decision-making skills). (VLID)3853532

Arm swing has been shown to lead to greater maximal speed and movement economy in cross -country skiing. The current study aimed to investigate how arm swing alters skiing mechanics and contributes to performance and acceleration of the athlete’s centre of mass (COM). While skiing on snow seven highly skilled cross -country skiers simulated V2 -alternate skating without using ski poles and with double or single arm swing and without arm swing . During leg push -off the linear momentum of the body increased due to arm swing. Simultaneously, linear momentum of the arm(s) decreased in arm swing trials, indicating a transfer of momentum from arms to the rest of the body and being more prevalent with double arm swing compared to single arm swing (all P < 0.05). Greater maximal skiing speeds were reached with single and double arm swing, while the forward lean angle, the force leading to acceleration of COM in skiing direction and the force effectiveness increased (all P < 0.05). The effects of less mass moving in single arm swing could be compensated by carrying out the arm swing faster, almost aligned in skiing direction and with a “long arm” pattern, indicating how arm swing can be conducted efficiently. peerReviewed

This study examined the influence of physical exercise on the relation between shooting accuracy and the phase of the cardiac cycle in which the shot is fired. Thirteen experienced biathletes (8 females, mean age 17 years) fired from the standing position at rest and right after a submaximal exercise on a bicycle ergometer. Shooting accuracy and the timing of each shot relative to the R-waves of the electrocardiogram (ECG) were recorded. Best shots (with greatest accuracy) and worst shots (with lowest accuracy) were fired prevalently in different phases of the cardiac cycle. In the rest condition, best shots were fired less frequently from 200 to 300ms and more frequently from 500 to 600ms after the R-wave, compared to worst shots. In the exercise condition, best shots were fired less frequently from 100 to 200ms after the R-wave and from 20% to 30% of the R-R interval, compared to worst shots. These findings support the hypothesis that shooting accuracy is influenced by the cardiac cycle phase due to the ballistocardiac recoil generated at each heartbeat. To achieve best results athletes could be trained (e.g. through biofeedback) to fire within a specific phase of the cardiac cycle. FWF P25000 (VLID)3119105

This study investigated how the fatigue caused by a 20-km simulated skating cross-country skiing race on snow affects the final spurt performance from a biomechanical perspective. Subjects performed a 100-m maximal skiing trial before and at the end of the simulated race. Cycle characteristics, ground reaction forces from skis and poles, and muscle activity from eight muscles were recorded during each trial. Results showed that subjects were in a fatigued state after the simulated race manifested by 11.6% lower skiing speed (P

Cross country sit skiing is a Paralympic discipline in which athletes due to physical impairment ski sitting on a sit-ski. The impairment influences performance directly and also through sitting position. Athletes with a better trunk control usually adopt a sitting position called “kneeing” in which the hip joints are higher than the knee joints. In contrast, athletes with high impact of impairment prefer a sitting position called “knee high” in which the hip joints are lower than the knee joints. Able bodied athletes skiing on the ergometer in these two sitting positions showed different performance. However, to the best of authors’ knowledge, no studies have examined performance, force production, and cycle characteristics of athletes with physical impairment who ski using different sitting positions. Therefore, the aim of the present study is to assess if athletes with physical impairment sitting in “kneeing” and “knee high” position perform differently while skiing. To obtain this purpose, a k-means cluster analysis was used to group ten male athletes according to their skiing performance in terms of maximal speed, generated force, and cycle characteristics. Cluster analysis results showed athletes aggregation in two clusters and a very high agreement between clusters analysis outcome and real athletes sitting position. Maximal speed and generated force were the most relevant variables for grouping athletes. Despite some limitations, these results suggest that the cluster analysis can be used to discriminate athletes according to their performance.