An electromyographic study of an all-out exercise on a cycle ergometer

The electromyograms of the vastus lateralis, the vastus medialis and the biceps femoris have been recorded with surface electrodes during an exhausting exercise on a Monark cycle ergometer, derived from the Wingate test (a 45 second all-out exercise against a braking force equal to 70 N) and during the velocity plateaus of submaximal exercises performed before this exhausting exercise on the same ergometer against the same resistance. This experiment has been carried out in order to study whether central fatigue occurs during an all-out anaerobic capacity test. One subject excepted (a former 800 m runner and road cyclist), there was a decrease in the electro expected integrated electromyogram (iEMG) during the exercise. The iEMG declines of the vastus medialis and the vastus lateralis were parallel and the revolution-to-revolution iEMG changes of the vastus medialis were positively correlated with those of the vastus medialis. These EMG changes suggest the occurrence of a central fatigue during this type of exercise. It was not possible to show a general trend for the effect of fatigue upon the EMG activity pattern of the biceps femoris because of large difference between subjects.