Power absorbed by the standing human body during whole-body vibration training

Absorbed power (AP) is a biodynamic response that is directly related to the magnitude and duration of vibration. No work has previously investigated the power absorbed by the standing human body during the exposure to vibration training conditions or otherwise. This article reports the power absorbed by the standing human body under whole-body vibration (WBV) training conditions. In this work, the force and acceleration used to calculate the apparent mass by Nawayseh and Hamdan (2019, "Apparent Mass of the Standing Human Body When Using a Whole-Body Vibration Training Machine: Effect of Knee Angle and Input Frequency," J. Biomech., 82, pp. 291-298) were reanalyzed to obtain the AP. The reported acceleration was integrated to obtain the velocity needed to calculate the AP. The effects of bending the knees (knee angles of 180 deg, 165 deg, 150 deg, and 135 deg) and vibration frequency (17-42 Hz) on the power absorbed by 12 standing subjects were investigated. Due to the different vibration magnitudes at different frequencies, the AP was normalized by dividing it by the power spectral density (PSD) of the input acceleration to obtain the normalized AP (NAP). The results showed a dependency of the data on the input frequency as well as the knee angle. A peak in the data was observed between 20 and 24 Hz. Below and above the peak, the AP and NAP tend to increase with more bending of the knees indicating an increase in the damping of the system. This may indicate the need for an optimal knee angle during WBV training to prevent possible injuries especially with prolonged exposure to vibration at high vibration intensities.