## 4 Discussion  
This investigation analyzed the effectiveness of a 5-week, nonpharmacological intervention (WBV) on lower-limb functionality and electromyographic activity during the 5 CST. Although the electromyographic profiles of the VL of both lower limbs did not change (\(p>0.05\)), 5 CST completion time improved after 5 weeks of WBVG. In the current study, subjects sat on an auxiliary chair with knees flexed and bare feet on the base of the VP, aiming to decrease the knee load impact. Previous research observed a decrease of pain level using the same position in patients with KOA [13], and this could justify the improvement in functionality of the lower limbs evaluated by the 5 CST, as shown in the current study. [PERSON] et al. [40] suggested that any type of short-term physical activity program carried out repeatedly and monitored can improve physical function and quality of life and reduce the pain related to KOA. Thus, the WBV can be considered a type of regular exercise capable of promoting the improvement of physical capacity in patients with KOA. Other studies present similar results concerning pain level and functional performance using the squat position on the VP. Prior research reported that a single bout of intermittent WBV (10 \(\times\) one minute of mechanical vibration with one minute rest) of 35 Hz and 4-6 mm significantly improved the time taken to complete the step test after 5 min of performed [41]. In longer-term investigations of WBVG, [PERSON] et al. [42] observed that KOA patients improved their functional test scores and Western Ontario and McMaster Universities OA Index (WOMAC) values. However, the improvements were not significantly different from the CG that performed squat training without WBVG. Another study involving 8 weeks of WBV training showed a significant increase in muscle strength and knee extension in women with KOA [43]. In a meta-analysis review [44], the authors concluded that 8 to 12 weeks of WBV training could be beneficial in rehabilitation programs, especially for KOA, leading to a decrease of the pain level and the enhancement of physical functions such as walking and balance, suggesting that the WBV is an effective and safe approach for this population. Despite the reduction in time taken to perform the 5 CST, which suggests an improvement of functionality, no significant differences were observed in sEMG RMS (\(\mu\)V) of the VL between pre- and postintervention for CON and WBVG. Similarly, other research found no significant difference in sEMG of KOA subjects that performed squats with or without WBV [45; 46]. In contrast, [PERSON] et al. [47] reported increased muscle activity in patients with KOA that were treated with localized muscle vibration, which is consistent with previous studies reporting that the vibratory stimulus increases neuromuscular activity [48; 49; 50]. Although no consensus is established, as the vibratory stimulus affects the neuromuscular system, it is suggested that the increase in sEMG activity is related to an excitatory response of the muscle spindles in consequence of the stretch reflex mechanism during WBV [48; 49; 50]. However, the current findings indicate that the excitatory responses of muscle fibers do not remain after the end of the protocol, since we observed a tendency of the amplitude of the sEMG to decrease in the group submitted to mechanical vibration. The strength of this study is related to the acquisition of information about the effect of WBV on functional responses evaluated by sEMG in a special protocol in which the individuals with KOA are seated in a comfortable position in an ancillary chair. This work has limitations that must be considered in the interpretation of the results. There are a myriad of different possibilities in selecting the biomechanical parameters, and to date there is still no optimal WBVG protocol. Moreover, the Ahlback grading, the osteoarthritis laterality, and the body mass index were not indicated as inclusion criteria.