Journal of Sports Science and Medicine
Journal of Sports Science and Medicine
ISSN: 1303 - 2968   
Ios-APP Journal of Sports Science and Medicine
Androit-APP Journal of Sports Science and Medicine
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©Journal of Sports Science and Medicine (2011) 10, 81 - 92

Research article
Changes in Quadriceps Muscle Activity During Sustained Recreational Alpine Skiing
Josef Kröll1,2, , Erich Müller1,2, John G. Seifert3, James M. Wakeling4
Author Information
1 Department of Sport Science and Kinesiology, University of Salzburg, Austria
2 Christian Doppler Laboratory “Biomechanics in Skiing”, Salzburg, Austria
3 Movement Science Laboratory, Montana State University, Bozeman, MT, USA
4 Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada

Josef Kröll
✉ Department of Sport Science and Kinesiology, University of Salzburg, Rifer Schlossallee 49, A-5400 Hallein/Rif, Austria
Email: josef.kroell@sbg.ac.at
Publish Date
Received: 20-09-2010
Accepted: 08-11-2010
Published (online): 01-03-2011
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ABSTRACT

During a day of skiing thousands of repeated contractions take place. Previous research on prolonged recreational alpine skiing show that physiological changes occur and hence some level of fatigue is inevitable. In the present paper the effect of prolonged skiing on the recruitment and coordination of the muscle activity was investigated. Six subjects performed 24 standardized runs. Muscle activity during the first two (PREskiing) and the last two (POSTskiing) runs was measured from the vastus lateralis (VL) and rectus femoris (RF) using EMG and quantified using wavelet and principal component analysis. The frequency content of the EMG signal shifted in seven out of eight cases significantly towards lower frequencies with highest effects observed for RF on outside leg. A significant pronounced outside leg loading occurred during POSTskiing and the timing of muscle activity peaks occurred more towards turn completion. Specific EMG frequency changes were observed at certain time points throughout the time windows and not over the whole double turn. It is suggested that general muscular fatigue, where additional specific muscle fibers have to be recruited due to the reduced power output of other fibers did not occur. The EMG frequency decrease and intensity changes for RF and VL are caused by altered timing (coordination) within the turn towards a most likely more uncontrolled skiing technique. Hence, these data provide evidence to suggest recreational skiers alter their skiing technique before a potential change in muscle fiber recruitment occurs.

Key words: Muscle coordination, recruitment, electromyography, wavelet analysis


           Key Points
  • The frequency content of the EMG signal shifted in seven out of eight cases significantly towards lower frequencies with highest effects observed for RF.
  • General muscular fatigue, where additional specific fibers have to be recruited due to the reduced power output of other fibers, did not occur.
  • A modified skiing style towards a less functional and hence more uncontrolled skiing technique seems to be a key issue with respect to the influence on muscle recruitment for applied prolonged skiing session.
 
 
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