Subjective ratings of whole-body vibration for single- and multi-axis motion

Abstract

The purpose of this research is to explore the use of whole-body vibration platforms commercially available in the health and sports sector. Experiments were conducted using two platforms providing a sinusoidal stimuli, one with a vertical (Platform 1) and one with a tilting action (Platform 2). A range of platform settings from 5 to 50 Hz were used. Comparison of these settings with the actual movement was made using a tri axial accelerometer mounted on the platforms to obtain the power spectrum density and magnitude of vibration (m/s2 r.m.s.) weighted and unweighted. The participants stood on each of the platforms with a bent knee (angle of 130.) for 30 seconds on each of 4 settings
in a randomised order. Following each stimuli the participants were asked to rate the intensity of the experience using a numeric category ratio (CR100). The range of frequencies and magnitudes measured were approximately 5 to 39 Hz and 1 to 60 m/s2 r.m.s. There was a positive correlation between mean subjective rating of intensity and magnitude of vibration. Subjective ratings of intensity per magnitude of vibration were greatest at 5 Hz and an increase in 1 m/s2 r.m.s.weighted was equivalent to approximately 8 units on the CR100 scale. At comparable magnitude and frequency there was no significant difference in subjective response between the platforms. No correlation between age or Body Mass Index (BMI) and subjective rating of intensity were observed.