Effect of Velocity on the Bilateral Deficit During Dynamic Knee Extension and Flexion Exercise in Females

Abstract

The bilateral deficit (BD) during force production mayresult from decreased activation of either slow-twitchor fast-twitch muscle fibers. The purpose of this studywas to investigate the effect of velocity on the BD andestimate the relative contribution of muscle fiber type tothe BD in untrained women. Twelve subjectsperformed three concentric reciprocal knee extension andflexion repetitions at isokinetic speeds of 60, 120, 180,240 and 360 deg/sec using both unilateral limbs andbilateral limbs. Results showed that the extension peaktorque BD decreased significantly (p 120 deg/sec, whereas the flexion peaktorque BD decreased significantly at speeds of 60 to > 180deg/sec. These results appear to demonstrate thatdecreased activation of primarily slow-twitch musclefibers may be responsible for the BD during dynamicknee extension and flexion exercise in women .* South Palm Orthopedics, 16244 South Military Trail, Suite 590,Delray Beach, FL 33484.t Florida Atlantic University, Human Performance Laboratory,Boca Raton, FL.t American Med-Care Center, Palm Springs, FL.§ Palm Beach County Fire Rescue, West Palm Beach, FL.Address reprint requests to Lee E. Brown, South Palm Orthopedics,16244 South Military Trail, Suite 590, Delray Beach, FL 33484.Accepted for publication August 1994.© 1994 Butterworth-Heinemann