Bilateral and Unilateral Neuromuscular Function and Muscle Cross-Sectional Area in Middle-Aged and Elderly Men and Women

volunteered as subjects for examination of muscle cross-sectional area (CSA), maximal voluntary forces, force-time curves, and electromyographic activity of the knee extensor muscles during bilateral and unilateral isometric contractions. The maximal bilateral knee extension force and the average CSA values in M50 were greater (p <.05) than in M70 and in W50 were greater (p <.05-.001) than those recorded for W70. The early forces in the force-time curve were greater (p <.05) for M50 than for M70 and in W50 were greater (p <.05) than in W70. The individual values of the CSA of the left and right quadriceps femoris (QF) correlated fp <.05-. 001) with the individual values of maximal unilateral knee extension forces in M50 (r =.87 and r =.87),M70(r =.61 and r =.80), W50(r =.79 and r =.58), and W70 (r =.56 and r =.54). When the force values were related to the CSA of the muscle, W70 demonstrated a lower (p <.05) value than the other three groups. Maximal voluntary bilateral forces didn't differ from those of the summed unilateral forces, and the maximal integrated EMG values during the bilateral and unilateral contractions of the same leg were also the same. The results suggest that the decline in maximal strength with increasing age could be related to the decline in the CSA of the muscle, but in older people, especially women, Strength decreases seemed to be multifactorial, including possibly a decrease in voluntary neural drive or changes i