Whole Body Vibration Induced Muscle Activity and Effect of the Changes in Length of Soleus Muscle and Angle of Ankle

Overview

Previous studies reported that myoelectrical activity increased during whole body vibration (WBV). The investigators hypothesized that the change in soleus muscle length does not affect the whole body vibration induced soleus reflex muscle activity but the change in ankle angle affects the whole body induced soleus reflex muscle activity. The purpose of this study is to test this hypothesis.

Eighteen healthy young adult men are planned to include in this study. Surface electrodes will be placed on the right soleus muscle's belly. The electrodes (10-mm in diameter, inter-electrode distance of 20 mm) were arranged in the direction of the muscle fibers. The skin overlying the muscle was shaved, light abrasion was applied, and the skin was cleaned using 70% alcohol. A piezo-electric accelerometer (LIS344ALH full-scale of ±6 g linear accelerometer, ECOPACK) will be placed on the achilles tendon and a force sensor (FC2331-0000-2000L Compression Load Sensor, France) will be placed under the right heel. All data will be recorded by PowerLab (data acquisition system, ADInstruments, Australia) device. The data were processed offline with a computer. All surface electromyography (SEMG) analyses were conducted using a software (LABCHART7 ver. 7.3.3; POWERLAB System, ADInstruments). All SEMG recordings were 80-500 Hz band-pass filtered. Root-mean-square values (RMS) were calculated from the filtered SEMG signal. WBV (PowerPlate Pro5) with high amplitude at 35 Hz will be applied. Participants were barefooted, and no sponge or foam was placed between the vibration platform and their feet. Participants will stand in different position with their knees locked during WBV. Their hips and knees were in a neutral position. Positions: Position-1: Upright standing on zero sloping vibration platform Position-2: Standing with 10 degrees ankle dorsiflexion on zero sloping vibration platform Position-3: Standing with 20 degrees ankle plantarflexion on zero sloping vibration platform Position-4: Upright standing on twenty degrees forward inclined vibration platform (angle angle will be 20 degrees ankle plantarflexion) Position-5: Leaning forward while standing on twenty degrees forward inclined vibration platform (angle angle will be neutral) Position-6: Upright standing on 10 degrees backward inclined vibration platform (angle angle will be 20 degrees ankle dorsiflexion) Position-7: Leaning backward while standing on 10 degrees backward inclined vibration platform (angle angle will be neutral) Sequence of the position will be random. Maximal voluntary contraction (MVC) was determined for each subject at the beginning of each position using magnitude of force between heel and vibration platform the when the subject attempted to activate the soleus muscle maximally. Then vibration exposure will be 30 seconds. The participants were instructed to relax their muscles throughout the recordings during WBV and were trained using electromyographic feedback to this end. WBV may impair the sense of balance and muscles may be activated to restore balance. To overcome this problem, the participants were familiarized with WBV with a 15 s trial session on the WBV device and they were asked to use the handles of the device to secure their balance.

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Interventions

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