Objective: This study aimed to investigate how whole-body vibration (WBV) and exercise and their interactions influenced leg muscle activity in elderly adults.
Study design: An experimental study with repeated measures design that involved a group of ambulatory, community-dwelling elderly adults (n=30; 23 women; mean age=61.4±5.3years).
Main outcome measures: Muscle activity of the vastus lateralis (VL), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius (GS) was measured by surface electromyography (EMG), while participants were performing seven different exercises during 4 WBV conditions (condition 1: frequency=30Hz, amplitude=0.6mm, intensity=2.25 units of Earth's gravity (g); condition 2: 30Hz, 0.9mm, 3.40g; condition 3: 40Hz, 0.6mm, 3.65g; condition 4: 40Hz, 0.9mm, 5.50g) and a no-WBV condition in a single experimental session.
Results: Significantly greater muscle activity was recorded in VL (3%-148%), BF (16%-202%), and GS (19% -164%) when WBV was added to the exercises, compared with the same exercises without WBV (p≤0.015). The effect of vibration intensity on EMG amplitude was exercise-dependent in VL (p=0.002), and this effect was marginally significant in GS (p=0.052). The EMG activity induced by the four WBV intensities was largely similar, and was the most pronounced during static erect standing and static single-leg standing.
Conclusions: The EMG amplitude of majority of leg muscles tested was significantly greater during WBV exposure compared with the no-WBV condition. Low-intensity WBV can induce muscle activity as effectively as higher-intensity protocols, and may be the preferred choice for frail elderly adults.
Keywords: Muscle activity; Older adults; Whole body vibration.
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