Changes of pedaling technique and muscle coordination during an exhaustive exercise.
OBJECTIVE
Alterations of the mechanical patterns during an exhaustive pedaling exercise have been previously shown. We designed the present study to test the hypothesis that these alterations in the biomechanics of pedaling, which occur during exhaustive exercise, are linked to changes in the activity patterns of lower limb muscles.


METHODS
Ten well-trained cyclists were tested during a limited time to exhaustion, performing 80% of maximal power tolerated. Pedal force components were measured continuously using instrumented pedals and were synchronized with surface EMG signals measured in 10 lower limb muscles.


RESULTS
The results confirmed most of the alterations of the mechanical patterns previously described in the literature. The magnitude of the root mean squared of the EMG during the complete cycle (RMScycle) for tibialis anterior and gastrocnemius medialis decreased significantly (P < 0.05) from 85% and 75% of Tlim, respectively. A higher RMScycle was obtained for gluteus maximus (P < 0.01) and biceps femoris (P < 0.05) from 75% of Tlim. The k values that resulted from the cross-correlation technique indicated that the activities of six muscles (gastrocnemius medialis, gastrocnemius lateralis, tibialis anterior, vastus lateralis, vastus medialis, and rectus femoris) were shifted forward in the cycle at the end of the exercise.


CONCLUSIONS
The large increases in activity for gluteus maximus and biceps femoris, which are in accordance with the increase in force production during the propulsive phase, could be considered as instinctive coordination strategies that compensate for potential fatigue and loss of force of the knee extensors (i.e., vastus lateralis and vastus medialis) by a higher moment of the hip extensors.
Dorel
Sylvain
S
Research Mission, Laboratory of Biomechanics and Physiology, National Institute for Sports (INSEP), Paris, France.
Drouet
Jean-Marc
JM
Couturier
Antoine
A
Champoux
Yvan
Y
Hug
François
F
D000328:Adult; D001642:Bicycling; D004576:Electromyography; D016552:Ergometry; D017079:Exercise Tolerance; D005260:Female; D006801:Humans; D007866:Leg; D008297:Male; D018763:Muscle Fatigue; D018482:Muscle, Skeletal; D010101:Oxygen Consumption; D019415:Torque