## 5 Discussion
[52] did not present significant differences in the pain level and physical function of individuals with KOA after an 8-week protocol with a vertical VP(squat training position, 20 Hz, and 2 mm). In addition, [PERSON] et al. [53] reported in an umbrella review that WBV exercises achieved moderate evidence for the improvement of KOA symptoms, but as a complementary intervention. [PERSON] et al. [25] and [PERSON] et al. [26], in metabolic syndrome individuals, also observed that a session of WBV exercises (frequency 5 Hz, with the same peak to peak displacement and position) decreased the level of pain, ATF, and the subjective perception of effort. [PERSON] et al. [54], in a different protocol, observed that vibratory training plus squat training (12 weeks, vertical platform, frequency from 35 to 40 Hz, 4 mm, and from 2.78 to 3.26 g) improved balance (static and dynamic), gait, and self-perception of pain in the elderly with KOA. However, [PERSON] et al. [55] observed that a WBV session on a triplanar (vertical) VP, with 35 Hz and the same peak-to-peak displacements, in a standing position with the knees slightly bent, did not improve the TUG test and did not affect the knee pain levels of individuals with KOA; two participants did not finish the protocol due to knee pain. To our knowledge, this is the first work that has investigated the effects of WBVE on pain levels, functionality, and perception of effort. Thus, the pain reduction and improvement in functionality, without changing the perception of the effort of individuals with KOA, need to be confirmed in well-designed longitudinal randomized controlled trials. Considering the evaluation of acute effects, in this current study, the tests before and after WBVEs were performed in a 10-min time window. It would also be interesting to analyze, in future studies, how long the acute effects are maintained, which was not possible in the present study. The strengths of the current work are the outcomes (pain level, functionality (TUG test), and flexibility), which are meaningful for the studied population, the rating of perceived exertion of KOA individuals, and the protocol with low frequency (5 Hz; with the individual in a sitting position in an ancillary chair to reduce the impact of the mechanical vibration overloading the knee joint). This position, in addition to offering the participant the possibility of comfortable and safe exercise, promotes better adherence to the proposed protocol since pain limits these individuals from the practice of regular physical activity. On the other hand, individuals with KOA have a higher risk of falls [10], which may compromise the participant's safety during the protocol in other positions. The results of this investigation are promising and can be considered of clinical importance in the treatment of KOA individuals. The limitations of this study are related to (i) the use of only one frequency in the intervention, (ii) the sole use of [PERSON]'s classification to evaluate the degree of KOA, (iii) the use of the LFI questionnaire considering both knees (not considering right and left knees separately), (iv) not using nuclear magnetic resonance imaging to evaluate the bone structure, (v) the vibration given to each patient, which was at the same level for every age, body mass, and intervention time (these conditions could be considered as bias), and (vi) the duration of the results, which was not investigated in a follow-up session. However, important findings were obtained.