Fig. 1.

Thigh muscle activation during an extension-flexion-extension cycle of the knee extension (KE) exercise. Electromyography (EMG) signal was processed by root mean square (RMS) algorithm and expressed as a percentage of the value obtained during maximal voluntary contraction (MVC). During the extension phase, RMS values for biceps femoris (BF) muscle were markedly lower than those for vastus lateralis (VL) and rectus femoris (RF) muscles. Substantially no muscle activation was observed for any muscle during flexion. These data confirm that knee flexors (BF) were not significantly involved during KE, and that the flexion phase was completely passive (see text for further details).