# Acute Effects of Whole-Body Vibration on Gait Kinematics in Individuals with Parkinson's Disease
## 4 Discussion
The absence of significant differences in these metrics following whole-body vibration (WBV) intervention may be attributed to several factors, including the relatively short duration and specific parameters of the WBV protocol employed, which might have been insufficient to elicit measurable changes in these critical gait features. Furthermore, since gait abnormalities in PD are influenced by complex neurophysiological mechanisms and clinical heterogeneity, variable responses to WBV are likely, making it plausible that longer or more intensive WBV protocols could yield more pronounced effects on stride length and double-support time. Moreover, the literature presents conflicting evidence regarding the effects of WBV on gait and mobility in PD patients. [PERSON] et al. (2014) [50] reported mixed findings regarding the effects of whole-body vibration (WBV) on mobility and balance in patients with [PERSON]'s disease. While some studies demonstrated positive outcomes, there was no clear evidence of superiority over placebo or other active interventions. The authors identified variability in WBV parameters and intervention duration as key limitations across the included studies. Similarly, a recent meta-analysis including nine randomized controlled trials found that WBV significantly improved motor function and walking stability but did not produce statistically significant improvements in balance or activities of daily living [31]. The superior performance of HS in parameters like propulsion dx, propulsion sx, and cadence may be attributed to its ability to enhance muscle engagement, neuromuscular activation, and proprioceptive control. Unlike WBV, HS enables participants to focus more effectively on body mechanics and alignment without the potential interference of vibratory stimuli, which could mask proprioceptive feedback or induce fatigue [42; 51]. Although WBV improves gait parameters in [PERSON]'s disease, half squats, being low-cost and easy to perform, offer similar or greater acute benefits and may serve as a practical alternative or complement to WBV. Finally, the effectiveness of WBV may be influenced by factors such as vibration frequency and amplitude, which can either enhance muscle activation or lead to premature fatigue [52]. Although our protocol (1 min at 30 Hz) was shown to elicit the highest reflex response in the vastus lateralis muscle during whole-body vibrations in half-squat position [32], we did not observe any additional or greater effects compared to isometric contraction. This may also depend on the nature of the study itself as it involved only an acute administration, neglecting the effect of a chronic exposure. [PERSON] et al. [17] reported that WBV training at a frequency of 35 Hz and amplitude of 2 mm increased walking speed and quality of life in individuals with PD. Similarly, [PERSON] et al. [12] found that WBV (at 25 Hz and amplitude of 7-14 mm) combined with conventional physiotherapy improved balance and gait velocity in PD. However, these studies did not compare the effect of vibration stimuli versus isometric contraction. Moreover, the characteristics of vibratory stimulation (frequency and amplitude) largely varied among the studies, providing high heterogeneity of study protocols. Therefore, there is a need for standardized vibrational parameters (frequency, amplitude, duration) to optimize neuromuscular coordination in PD. Our findings suggest that WBV may positively influence gait speed and pelvic tilt, and its application is well tolerated by individuals with PD who may be more susceptible to neuromuscular fatigue [53]. This study has some limitations. In our study, we have considered only participants in stages 1-2 of the H-Y scale; therefore, we cannot determine the effectiveness of the propose experimental conditions in participants with more severe Parkinson's disease.