Optimal Vibrational Frequency And Displacement To Elicit Maximal Skeletal Muscle Activation

Abstract

Whole body vibration (WBV) has been shown to increase neuromuscular activity; however, there are limited data examining the training protocol that elicits the highest muscular activity during WBV. PURPOSE: This study analyzed the electrical activities of the vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) during differing WBV protocols. METHODS: 30 women, 15 athletes (ATH) and 15 non-athletes (NATH), ages 18–35 years, participated in this study. EMG activity was examined during an isometric squat on a WBV platform. The squat was performed at a knee angle of 2.10 rad with the subject either flat footed (SQF) or standing on her toes (SQT). Two displacements (2mm, 5mm) and 4 frequencies (30, 35,40 and 50 Hz) of WBV were tested. Test bouts lasted 10 seconds. A 2 (stance) × 2 (displacement) × 4 (frequency) repeated measures ANOVA was used to examine differences among conditions. A minimum of 2 minutes rest was allotted to reduce the potential for residual fatigue. All test conditions were randomized and administered on the same day. RESULTS: When comparing the SQF baseline to all testing conditions the most consistent significant differences were seen during high displacement at 30 Hz SQF and 30 and 35 Hz SQT. Significant differences were also observed between the SQT baseline and SQF high displacement at 30, 35 and 40 Hz. Additionally significant differences were detected between the SQT baseline and SQT high displacement at 35 and 40 Hz and low displacement at 40Hz. CONCLUSION: Our data indicate that the most effective condition for WBV during SQF was a high displacement at 30 Hz, while the SQT condition that elicited the most muscular activity was high displacement at 35 Hz.