Dependence of palmar sweating response and central nervous system activity on the frequency of whole-body vibration

Objectives This study was carried out to determine the effects of the frequency of whole-body vibration on palmar sweating response and the activity of the central sympathetic nervous system. Methods Palmar sweating volume was measured on the right palm of six healthy men before and during 3 minutes of exposure to sinusoidal whole-body vibration at three different frequencies (16, 31.5, and 63 Hz). The whole-body vibration had a frequency-weighted, root mean square (rms) acceleration magnitude of 2.0 m/s(2). As the index of the activated central sympathetic nervous system, saliva level of 3-methoxy-4-hydroxyphenylglycol (MHPG) was analyzed before and immediately after each vibration exposure. Results Each vibration frequency induced a palmar sweating response, that of 31.5 Hz being the largest. However, no significant difference was found between the three vibration conditions. Saliva MHPG increased in all the vibration exposures, and the largest change was observed at 31.5 Hz, the difference being significant. Conclusions Acute exposure to whole-body vibration induced a palmar sweating response and activated the central sympathetic nervous system. The effects on the central nervous system were found to be dependent on the frequency of the vibration.