Whole-body vibration effect on muscle activations: which one is the most effective, low frequency or high frequency?

Purpose: Whole Body Vibration (WBV) is a practice that passively applies mechanical oscillations to an individual from a support surface. The tonic vibration reflex response depends on the vibration localization, frequency, amplitude, and initial length of the muscle, but there is no consensus on what the optimal frequency should be. This study was conducted to examine the activation differences of lower extremity muscles at low and high frequencies during squat exercise in WBV. Methods: This study involved 16 healthy individuals (Age = 23.66 ± 2.33 years, Body Mass Index = 22.59 ± 3.86 kg/m2). WBV application was performed on a vertical vibration platform (GLOBUS Physioplate®). Participants performed static half-squats on WBV for 20 seconds under vibration-free and vibrating (20 Hz and 60 Hz; 2-3 mm amplitude) conditions. An 8-channel Electromyography (EMG) Noraxon MiniDTS system was used to measure the activation of the Gluteus Medius (GMed), Gluteus Maximus (GMax), Vastus Lateralis (VL) And Vastus Medialis (VM) Muscles. Results: It was observed that there was a disparity between the two frequencies for the activation of the VM, VL, GMed, and GMax muscles (p = 0.002, 0.000, 0.001, 0.01, respectively). Vibration frequencies of GMax, GMed, VL, and VM muscle activities at high frequency were increased compared to low frequency. Conclusions: Physiotherapists and coaches should prefer high frequencies in WBV applications when they need to improve neuromuscular response.