# Acute Effects of Whole-Body Vibration on Gait Kinematics in Individuals with Parkinson's Disease
## 4 Discussion
However, since no significant differences were found between WBV and HS, it remains unclear whether WBV provides unique advantages in this regard or if the observed improvements are primarily due to the half-squat exercise itself. Additionally, increased muscle strength from isometric training reduces pelvic tilt and obliquity during gait, contributing to more energy-efficient movement patterns [40]. These results, although based on a different protocol [40] than ours, could explain why pelvic tilt significantly increased after the HS and WBV conditions compared to CC, although no significant difference was found between HS and WBV. Regarding the effects of vibration on pelvic tilt, [PERSON] et al. [41] investigated the effects of three different vibration frequencies and pelvic positions while participants stood quietly on a WBV platform. To assess the muscle activity of the participants, electromyography analysis was conducted, indicating that WBV positively influenced muscle activity (i.e., upper trapezius, erector spinae, rectus abdominis, external oblique, gluteus maximus, rectus femoris, semitendinosus, medial gastrocnemius), with effects varying with vibration frequency and pelvic positioning. The authors recommended using higher WBV frequencies (20 Hz) to improve muscle strength and incorporating a posterior pelvic tilt during WBV, as it is shown to be significantly more effective in strengthening and training muscles related to core stability. Although based on a different intervention, this study is consistent with our findings and may explain the positive effects of the vibration on this variable [41]. The results for cadence suggest that HS was superior to both WBV and CC, with no significant differences between WBV and CC. This finding suggests that while WBV may help maintain cadence, it does not necessarily enhance it beyond what can be achieved through conventional exercise. Maintaining a consistent walking rhythm is crucial for individuals with PD, as gait irregularities increase fall risk and reduce overall mobility [18; 36]. The superior performance of HS in this parameter may be attributed to the greater proprioceptive feedback and neuromuscular control facilitated by isometric movement without external vibratory stimuli [42]. Previous studies show that isometric exercises, particularly those targeting the trunk and lower limb muscles, lead to improvements in gait velocity and cadence. For instance, isometric trunk exercises significantly enhance gait speed and cadence by improving core stability and neuromuscular control, both of which are critical for maintaining rhythm and balance during walking [41; 43]. These results, although based on a different protocol, could explain why cadence significantly improved after the HS condition compared to WBV and CC. Moreover, the observed superior performance of the isometric half-squat (HS) condition in propulsion and cadence compared to whole-body vibration (WBV) suggests that sustained isometric contractions may induce neural adaptations that more effectively enhance motor output than acute WBV exposure. Isometric contractions are known to promote increased motor unit recruitment and firing rates, leading to enhanced corticospinal excitability and improved muscle activation patterns [44; 45]. In contrast, WBV primarily stimulates muscle spindles and Ia afferents, eliciting reflexive muscle contractions via the tonic vibration reflex, which may produce transient neuromuscular facilitation but less pronounced voluntary motor control adaptations in the short term [15; 46]. Neural adaptations to isometric training involve central nervous system plasticity, including increased cortical drive and improved synchronization of motor units [47; 48], which may translate into more efficient gait propulsion and cadence improvements [49]. Therefore, the acute WBV benefits might be overridden by the more robust neural activation elicited by sustained isometric contractions.