BACKGROUND: Motor nerve function decreases with age and can cause abnormalities in motor function. Using newly designed methods, we used evoked electromyograms to evaluate change in motor nerve function.

MATERIAL AND METHODS: Motor function was assessed by grip strength, timed up-and-go test, 5-m normal walk, and 5-m fastest walk. In addition, motor nerve conduction velocity was calculated by measuring latency differences (NCV) in elderly and young subjects. We also investigated motor nerve conduction velocity by correlation coefficient (NCVCC) and the difference between NCV and NCVCC (DNCV).

RESULTS: Significant differences were observed in the motor function of elderly and young persons in grip strength, the timed up-and-go test, and the 5-m fastest walk; however, no difference was observed in the 5-m normal walk test. NCVCC was lower than NCV in both elderly and young. The correlation coefficient peak of the NCVCC calculation was lower in elderly than in young. A negative correlation was observed between correlation coefficient peak and DNCV in elderly subjects.

CONCLUSIONS: NCVCC compares the overall shape of compound muscle action potential and reflects not only the fastest motor unit, but also the motor nerve conduction velocity of other motor unit components. A significant negative correlation between DNCV and the correlation coefficient peak was observed only in elderly subjects, suggesting that older individuals, including those that maintain a high level of physical strength, experience a loss of motor nerve function. Thus, changes in motor nerve function among elderly persons can potentially be further examined for clinical use.

Keywords: Motor Neurons - physiology, Motor Activity - physiology, Health, Aged, 80 and over, Neural Conduction - physiology, Pilot Projects, Reaction Time