Electromyographic responses of lower leg muscles to upward toe tilts as a function of age

EMGs were recorded from the gastrocnemius and anterior tibialis muscles of 77 adult subjects in response to perturbation of stance by upward toe tilts. Subjects aged 22-88 y were initially grouped in seven decades (20s-80s). Each presented a history free of ear disease, eye disease not correctable by lenses, neurological disease, and persistent difficulty with balance or dizziness. All demonstrated functionally normal balance for their age on routine dynamic posturography. EMG recordings yielded onset and offset latencies, durations, and integrated amplitudes of the short and medium latency responses of the gastrocnemius and the long latency responses of the anterior tibialis. Analysis of the data revealed statistically significant left-right differences in amplitude of response and statistically significant height, gender, and age effects. Procedural issues were discussed; data were summarized for normative purposes; and suggestions were made for dealing with statistically significant differences in a clinical environment.