International Journal of Physiotherapy and Rehabilitation, October 2010, Vol. 1, Issue 1, 30-40 / J. Hong, K. Kipp, S.T. Johnson, M.A.Hoffman / ˝2010, International Journal of Physiotherapy and Rehabilitation

Effects of 4 weeks whole body vibration on electromechanical delay, rate of force development, and presynaptic inhibition.

1) Department of Exercise Science, Willamette University, 900 State Street, Salem, OR 9730; 2) Department of Physical Medicine and Rehabilitation University of Michigan, 325 E. Eisenhower Ste. 100 Ann Arbor, MI 48109; 3) Department Nutrition and Exercise Science, Oregon State University 3, Corvallis OR 97331 / Email: jhong@willamette.edu

Abstract

Objective: Long-term functional changes after whole-body vibration (WBV) training have been attributed to adaptations in the neuromuscular system. The present study examined the effect of four weeks of WBV training on muscle function outcome variables [(rate of force development (RFD), electromechanical delay (EMD)], and spinal control mechanisms (pre-synaptic inhibition).

Method: Forty young individuals with no history of lower leg injuries were randomly assigned to an experimental or control group. The experimental group received WBV training (three bouts of two minutes, three times a week) for four weeks. During each of the training sessions, the subjects stood on the vibration platform with the knees slightly flexed. The control group performed periods of standing in the same position as the experimental subjects.

Results: After four weeks of WBV training, the experimental (WBV) group demonstrated a significant improvement in electromechanical delay (EMD). The results also showed a significant group Å~ test interaction for RFD and intrinsic pre-synaptic inhibition (IPI) over the course of the study.

Conclusion: Enhanced neuromuscular activation (EMD and RFD) and increased spinal reflex gain followed by 4 weeks of WBV training indicate that WBV training might be used not only for athletes engaged in sports that require explosive type of muscular activation, but also for the elderly individual who need to exert a rapid rise in muscle force in injury related situations.

Keywords: whole body vibration, neurological adaptation, rate of force development, electromechanical delay, pre-synaptic inhibition, H-reflex