Introduction: In Paralympic sit ski athletes core stability is essential for forward propulsion. As these athletes can only use arm and trunk for double poling, well-coordinated muscular activation is necessary. Depending on the level of impairment, sit skiers can take different sitting positions which may affect athletic performance. Whether the timing of muscle activation and performance is affected by sitting position is not clear at present. The aim of the present study was to examine muscular activation of trunk and arm muscles with healthy subjects in sitting positions commonly observable in disabled sit skiers. Methods: 10 healthy male XC skiers (20±3y) participated in an ergometer test (concept2 ski ergometer, USA), simulating double poling in sit skiers. Poling forces were recorded synchronously with surface EMG from triceps brachii (TRIC), m. rectus abdominis (RECab) and m. erector spinae (ES) muscles. EMG was normalized to MVC and mean EMG amplitude (m%MVC) was calculated 200ms before (PRE) and during poling (POL). Maximum velocity poling at 4 sitting positions (P1-P4) on an adjustable chair was tested. P1 represent normal, P2 with knees higher than hip, P3 kneeing and P4 with straight leg. Results: Maximum poling velocity was achieved in P3 with 6.6 ± 0.24 m/s and slowest in P2 with 4.2 ± 0.27 m/s (P<0.05). Mean values over all 4 positions show that the RECab was activated -136±16ms before poling. TRIC was activated little bit earlier (-10±1ms) whilst ES is activated at the end of poling (187±12ms). Differences between sitting positions did not show any statistical significance in muscle onset in any of the muscles. M%MVC for TRIC showed a range from 8% (P1) to 13% (P2) in PRE and 46% to 60% during POL. RECab showed 19% (P1) to 25% (P3) in PRE and 16% to 26% during poling POL. Discussion: Kneeing (P3) seems to be the most effective position to achieve the highest velocity and highest EMG at the ergometer. The onset of muscle activation, however, was in all positions the same. Higher activation of abdominal muscle before starting of poling s underlines the importance, that core stability is one requirement to achieve best poling performance. It is hypothesized, that such a movement pattern should also be claimed in disabled athletes sitting in sledges. This result may also have impact to the classification process and performance related categories (Van de Vliet, 2012) which are required to guaranty a fair competition among persons with equal or similar levels of impairment.
© Copyright 2014 19th Annual Congress of the European College of Sport Science (ECSS), Amsterdam, 2. - 5. July 2014. Julkaistu Tekijä VU University Amsterdam. Kaikki oikeudet pidätetään. / Kääntänyt https://www.DeepL.com/Translator