Whole-body vibration training improves flexibility, strength profile of knee flexors, and hamstrings-to-quadriceps strength ratio in females
Objectives: Short-term whole-body vibration training (WBVT) has emerged as an exercise method for improving neuromuscular performance and has been proposed for injury prevention and rehabilitation. This study investigated the effects of a short-term (<= 2 months) WBVT program using a side-to-side vibration on: (i) strength profile of knee extensors (ME) and flexors (KF), (ii) "functional" hamstrings-to-quadriceps ratio (ECCKF/CONKE), (iii) flexibility and (iv) vertical jumping performance (VJ). Furthermore, we explored the retention of performance gains 21 days following WBVT. Design: Randomized-controlled trial. Methods: Twenty-six moderately active females (20.40 +/- 0.27 years) were assigned to a vibration (VG) or a control group (CG). The short-term WBVT program consisted of sixteen-sessions on a side-to-side vibration platform (frequency: 25 Hz, amplitude: 6 mm, 2 sets x 5 min). Isokinetic and isometric peak torque of KE and KF, ECCKF/CONKE, flexibility, and VJ were measured pre, 2 days post, and 21 days following the cessation of WBVT. Results: Post-training values of flexibility, isokinetic and isometric peak torques of KF and ECCKF/CONKE ratio were higher than pre-training values in VG (p < 0.05); however, they remained unchanged in CG. Post-training values were greater in VG vs. CG (p < 0.05). Twenty-one days following WBVT, post-training values were no longer significantly different than pre-training values. The short-term WBVT program had no effect on strength profile of KE and on VJ. Conclusions: A short-term side-to-side WBVT program improved flexibility, the strength profile of knee flexors, and the "functional" hamstrings-to-quadriceps ratio in moderately active females. Coaches and clinical practitioners should consider this type of training as an effective exercise mode for improving the strength asymmetry of reciprocal muscles at the knee joint. (C) 2012 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.