Changes in the Motor Unit Number with Aging

Abstract

The decline in the motor unit number of the upper limb muscles with advancing age was reported in the previous studies using different techniques and they confirmed that the magnitude of the decline in the motor unit number with age has varied. The aim of this study was to determine the mean values of the motor unit number estimates and the magnitude of the decline in the motor unit number in the tenar muscles until age 60. In our study we examined the motor unit number estimates in the tenar muscles in healthy volunteers aged 21 -60 by using incremental technique. We found a decline in the motor unit number with advancing age and a significant decline was seen after fourth decade. In the diseases in which the number of motor units has an important role for determining the diagnosis, severity and following the course of the disease, we must take care to the patient's age and the muscle.