The Effect of Neural Drive on Bilateral and Unilateral Isometric Knee Extensions

Abstract

The bilateral limb deficit (BLD) phenomenon is the difference in the maximal or near maximal force generating capacity of muscles when a muscle is contracted alone or in unison with another muscle. While the BLD has been shown to occur in various muscle groups and movement patterns, surprisingly the source of the BLD remains unknown.

The interpolated twitch technique is a widely used measure of voluntary activation of muscle. It involves interjecting a maximal electrical stimulus onto contracting muscle to determine if all the motoneurons have been recruited or if some are not firing impulses at the optimal frequency for force generation. Minimal studies have used twitch interpolation to examine the BLD and the results have been equivocal.

This work examines the contribution of neural mechanisms during bilateral and unilateral isometric knee extension contractions to determine if neural drive is compromised during bilateral contractions. Preliminary results are presented.