Physiological and functional effects of acute low-frequency hand-arm vibration

The effects of low frequency of vibration have not been widely studied in the scientific literature, yet humans are exposed to such environmental stress everyday. The purpose of this investigation was to examine the physiological responses to low-frequency upper-body limb vibration. Fourteen healthy men were exposed to 1 hour of bilateral hand-arm vibration and control (no vibration) conditions in a counter-balanced, cross-over design separated by 2 days. Subjects gripped handles that were coupled to a vibrating device, which oscillated in an anterior to posterior direction at a constant frequency of 7.5 Hz and a displacement of 0.38 cm. A series of tests were performed prior to and following the vibration to assess cardiovascular response, visual acuity, tremor of the hand and fingers, grip strength, anticipation response, limb girths, and a movement repositioning task. There were significantly (p < or = 0.05) more visual errors postvibration compared with postcontrol on a standardized vision chart. Tremor was significantly reduced during the vibration compared with the control condition. There were no significant changes in grip strength. Mean anticipation response time was significantly increased during the control condition (+3.3%) but not after vibration (+1.0%). There was a significant improvement in the movement repositioning task after vibration compared with control. Heart rates during the vibration protocol were not significantly higher than the control condition. No significant increases in limb size representative of swelling were observed. These data indicate that exposure to 1 hour of low-frequency hand-arm vibration has only minor effects on physiological function.