AJP - Regulatory, Integrative and Comparative Physiology, Vol 233, Issue 1 8-14, Copyright © 1977 by American Physiological Society
Involuntary ankle oscillations from normal subjects
R. N. Stiles and R. R. Rietz
Spectral analysis of ankle tremor records obtained from normal seated
subjects during continuous elevation of the heel for 10-45 min revealed
that the root-mean-square (rms) displacement amplitude of the tremor
increased from minimum values of about 4 micronm to values as large as
4,000 micronm. Associated with this increase in the displacement amplitude
was a systematic decrease in the tremor frequency from values of 7-8 Hz to
values of 5-6 Hz. Spectral analysis of demodulated soleus EMG records
indicated that the rms value of this EMG (calculated at the tremor
frequency) and the rms displacement of the tremor are related by a power
function, with the rms value of the EMG increasing over a range of about
4-40 micronV as the tremor displacement increased from about 4 to 4,000
micronm. The negative relation between frequency and rms displacement
amplitude values for postural ankle tremor was similar to that found
previously for postural hand tremor.
