Concentric and eccentric force-velocity relationships during electrically induced submaximal contractions.

The purpose of this investigation was to examine the force-velocity relationship during electrically induced, submaximal concentric and eccentric contractions of the quadriceps femoris muscle. Thirty female subjects with no history of knee pathology participated in the study. Force was measured on an isokinetic dynamometer and the quadriceps femoris muscle was electrically stimulated by use of a medium frequency current generator. Subjects were stimulated at 30% of their maximum voluntary isometric force. Four velocities were tested (30 degrees, 90 degrees, 120 degrees and 180 degrees/sec) during both concentric and eccentric contractions. The relationship between force and velocity was examined with an analysis of covariance. The regression model describing the force-velocity relationship for concentric contractions was significant (p < 0.0001) with an R2 of 0.96 and a slope of -0.76 (p < 0.0001). The regression model describing the force-velocity relationship for eccentric contractions was significant (p < 0.0001) with an R2 of 0.91 and a slope of 0.4 (p < 0.0001). The relationship between force and velocity during electrically induced, submaximal concentric and eccentric contractions were similar to in vitro studies that have examined this relationship during shortening and lengthening contractions.