The Acute Effects of Different Intensity Whole-Body Vibration Exposure on Muscle Tone and Strength of the Lower Legs, and Hamstring Flexibility: A Pilot Study

Abstract

Context: The research on the change in properties of the lower leg muscles by different intensity sinusoidal vertical whole-body vibration (SV-WBV) exposures has not yet been investigated. Objective: The purpose of this study was to determine effect of a 20-minute different intensity SV-WBV application to the ankle plantar flexor and dorsiflexor muscles properties and hamstring flexibility. Design: Prospective preintervention–postintervention design. Setting: Physiotherapy department. Participants: A total of 50 recreationally active college-aged individuals with no history of a lower leg injury volunteered. Interventions: The SV-WBV was applied throughout the session with an amplitude of 2 to 4 mm and a frequency of 25 Hz in moderate-intensity vibration group and 40 Hz in a vigorous-intensity vibration group. Main Outcome Measures: The gastrocnemius and tibialis anterior muscle tone was assessed with MyotonPRO, and the strength evaluation was made on the same lower leg muscles using hand-held dynamometer. The sit and reach test was used for the lower leg flexibility evaluation. Results: The gastrocnemius muscle tone decreased on the right side (d = 0.643, P = .01) and increased on the left (d = 0.593, P = .04) when vigorous-intensity vibration was applied. Bilateral gastrocnemius muscle strength did not change in both groups (P > .05). Without differences between groups, bilateral tibialis anterior muscle strength increased in both groups (P < .01). Bilateral gastrocnemius and tibialis anterior muscle tone did not change in the moderate-intensity vibration group (P > .05). Flexibility increased in both groups (P < .01); however, there was no statistically significant difference between the groups (d = 0.169, P = .55). Conclusions: According to study results, if SV-WBV is to be used in hamstring flexibility or ankle dorsiflexor muscle strengthening, both vibration exposures should be preferred. Different vibration programs could be proposed to increase ankle plantar flexor muscle strength in the acute results. Vigorous-intensity vibration exposure is effective in altering ankle plantar flexor muscle tone, but it is important to be aware of the differences between the lower legs.