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JOURNAL
OF
SPORTS SCIENCE &
MEDICINE
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Research
article
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CHANGES IN QUADRICEPS MUSCLE ACTIVITY DURING SUSTAINED RECREATIONAL ALPINE SKIING |
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Josef Kröll1,2  ,
Erich Müller1,2, John G. Seifert3 and James M. Wakeling4 |
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1Department of Sport Science and Kinesiology, University of Salzburg, Austria, 2Christian Doppler Laboratory "Biomechanics in Skiing", Salzburg, Austria, 3Movement Science Laboratory, Montana State University, Bozeman, MT, USA, 3Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada |
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© Journal of Sports Science and Medicine (2011) 10, 81 - 92 |
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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. |
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