Study of age changes in the motor units of the first dorsal interosseous muscle in man

The effect of ageing on the threshold firing rate of motor units from the first dorsal interosseous muscle was investigated. Two groups of 9 healthy male subjects between the ages of 20-29 and 60-69 years took part in the study. The threshold firing rate of motor units in young subjects showed close agreement with previous observations. However, a significant decrease was found in the older age group and, in addition, these units showed a prolongation of their contraction times, confirming our previous findings from this muscle. These results are discussed in relation to changes previously reported in human skeletal muscle and may indicate a functional change of the muscle with age.