The influence of unilateral electrical muscle stimulation on motor unit activity patterns in atrophic human quadriceps.

The efficacy of electrical muscle stimulation to restore motor function was investigated in fifteen males who described prior knee surgery/injury. Persisting strength imbalance between limbs related also to reduction in cross-sectional area of the affected quadriceps, as assessed by computed tomography of the midthigh. Subjects underwent a four-week programme of daily electro-motor stimulation with repeated assessment of force production by the knee extensors, correlated with surface electro-myography. Results showed no change in quadriceps cross-sectional area over the course of the study, however, significant improvements in force production for both limbs were achieved, accompanied by alteration in motor unit activity patterns to suggest that neural efficiency of motor unit activation (synchronization) may account for the improvements, as opposed to a marked morphological contribution.