Transmissibility of whole-body vibration to lower limb joints and its immediate impact on the center of pressure sway in elderly women

Objective Whole-body vibration (WBV) is a promising alternative for obtaining therapeutic benefits in the musculoskeletal system for elderly people. The study aimed to compare the transmissibility at the ankle, knee, and hip regions during WBV at different frequencies (20 and 40 Hz) and amplitudes (2 and 4 mm). Additionally, the immediate effects of WBV on the center of pressure (CoP) sway were also assessed. Methods In this single-group repeated-measures study, twenty elderly women were exposed to different combinations of frequencies (20 and 40 Hz) and amplitudes (2 and 4 mm) of WBV. The CoP sway was assessed immediately after the different modes of WBV. Results The results showed the transmissibility at the lower limb joints was higher at a frequency of 20 Hz compared to 40 Hz (P < 0.05). Increasing the WBV amplitude at the frequency of 20 Hz caused a significant decrease in transmissibility and did not cause a significant difference at the frequency of 40 Hz. Additionally, immediately after WBV with frequencies of 20 and 40 Hz and amplitude of 4 mm, there was an increase in the path, velocity, and amplitude of CoP sway in the anterior-posterior (A-P) direction (P < 0.05). Conclusion The findings indicate that using higher frequencies and amplitudes of WBV does not guarantee effective transmission of vibration to the lower limb. The ankle, knee, and hip joints exhibited the highest level of transmissibility when subjected to WBV at a frequency of 20 Hz and an amplitude of 2 mm. Additionally, WBV may lead to temporary instability in the anterior-posterior (A-P) direction, which should be considered in high-risk individuals, to prevent any immediate negative effects.