Functional quality assessment of whole-body vibration training devices based on instantaneous amplitude and frequency of photogrammetric vibration measurements.

The practical use of whole-body vibration training (WBVT) and such research may be negatively influenced by generated vibrations with amplitudes, frequencies, and/or patterns that deviate from preset adjustments on WBVT devices. This study examined whether prolonged regular use can generate respective deviations. Four WBVT devices, used for 19 months in a research project on the effects of WBVT, were analyzed using photogrammetry before start of the research project and after 19 months. Divergences between preset and measured amplitudes and frequencies were calculated for all measurements. To quantify how well the output of devices correlates with the target setting, the vibration characteristics were calculated. In particular, exact long-term measurements related to the vibration amplitude is conducted and analyzed for the first time, which has been found as an important measure of the device functional quality. One device had a significantly (p<0.01) larger machine run time than the other three. This one showed the most pronounced signs of functional impairments concerning instantaneous amplitudes, frequencies and the mode of vibration after prolonged use. These results based on photometric measurements underline again that prolonged use can result in divergences between preset and actual applied amplitudes, frequencies, mode of vibration and other accuracy measurement metrics.

Deviations in frequency and mode of vibration in whole-body vibration training devices with long-term and regular use.

Research regarding whole body vibration training (WBVT) and its practical use may be hindered by the fact that WBVT devices generate frequencies and/or modes of vibration different from their preset adjustments. This research aimed to clarify whether prolonged regular use can generate such deviations in frequency and mode of vibration. Three WBVT devices, each used for approximately 13 months in two research projects, were tested with an accelerometer before start of the 1st study, after four months, and after 13 months (the completion of the 2nd study). Divergences between the preset and measured frequencies were calculated for all measurements. Furthermore, the total harmonic distortion (THD), an index for signal deviations from a perfect sine wave, and the sum signal-to-modulation-noise-ratio (SMNR), an indicator of fidelity, were recorded. One device had a significantly larger machine run time than the other two, and it displayed the most pronounced signs of impaired function concerning frequency, mode of vibration, and random variability (SMNR) after prolonged use. These results indicate that prolonged use will result in divergences between the preset and actual applied frequencies as well as in the mode of vibration and other accuracy measurements.