Purpose: Excessive, chronic whole-body vibration (WBV) has a number of negative side effects on the human body, including disorders of the skeletal, digestive, reproductive, visual, and vestibular systems. Whole-body vibration training (WBVT) is intentional exposure to WBV to increase leg muscle strength, bone mineral density, health-related quality of life, and decrease back pain. The purpose of this study was to quantitatively evaluate vibration exposure and biodynamic responses during typical WBVT regimens.
Methods: Healthy men and women (N = 16) were recruited to perform slow, unloaded squats during WBVT (30 Hz; 4 mm p-p), during which knee flexion angle (KA), mechanical impedance, head acceleration (Harms), and estimated vibration dose value (eVDV) were measured. WBVT was repeated using two forms of vibration: 1) vertical forces to both feet simultaneously (VV), and 2) upward forces to only one foot at a time (RV).
Results: Mechanical impedance varied inversely with KA during RV (effect size, ηp2: 0.668, P < 0.01) and VV (ηp2: 0.533, P < 0.05). Harms varied with KA (ηp2: 0.686, P < 0.01) and is greater during VV than during RV at all KA (P < 0.01). The effect of KA on Harms is different for RV and VV (ηp2: 0.567, P < 0.05). The eVDV associated with typical RV and VV training regimens (30 Hz, 4 mm p-p, 10 min·d−1) exceeds the recommended daily vibration exposure as defined by ISO 2631-1 (P < 0.01).
Conclusions: ISO standards indicate that 10 min·d−1 WBVT is potentially harmful to the human body; the risk of adverse health effects may be lower during RV than VV and at half-squats rather than full-squats or upright stance. More research is needed toexplore the long-term health hazards of WBVT.
1Wyle Laboratories, Inc., Houston, TX; 2Human Performance Laboratory, University of Houston-Clear Lake, Houston, TX; 3Laboratory of Integrated Physiology, University of Houston, Houston, TX; 4Department of Physical Therapy, Hardin-Simmons University, Abilene, TX; and 5Human Adaptations and Countermeasures Division, National Aeronautics and Space Administration, Houston, TX
Address for correspondence: Andrew F. J. Abercromby, Ph.D, Wyle Laboratories, Inc., 1290 Hercules Drive, Houston, TX 77058; E-mail: firstname.lastname@example.org.
Submitted for publication October 2006.
Accepted for publication May 2007.