## 4 Discussion  
The underlying etiology of MetS is multifactorial, however, they are not well known, but sedentary lifestyles and unhealthy dietary habits favor the appearance of MetS [45]. Considering the high prevalence and strong and undesirable complications, early identifying and controlling the modified risk factors are key prevention methods to counter the development of MetS and its progression to CVD. It is relevant to point out that, to our knowledge, this is the first work that was performed to evaluate the effect of WBV exercise in sleep quality of MetS individuals. As it was hypothesized that the WBV exercise would be able to improve the sleep quality of MetS individuals, the quality of sleep was improved (PSQI) and a reduction of daytime sleepiness (ESS) in the MetS was found due to a protocol with variable frequencies (5-16 Hz) of WBV. A protocol with fixed frequency (5 Hz) also improved the quality of sleep (PSQI). It was shown (Table 1) that the 6-week intervention with WBV exercise with variable frequencies (from 5 up to 16 Hz) (VF group) did not alter significantly the BMI, NC, SBP, and DBP. The same finding was verified in the individuals with fixed frequency (5 Hz). These findings agree with other studies. [PERSON] et al. [46], in a study of six months, have shown that aerobic exercise training is enough to elicit improvements in vascular structure and function in African Americans, even without alterations on BP measurements (SBP and DBP) in African Americans. Moreover, [PERSON] et al. [31] have reported that, in individuals with MetS exposed to acute WBV exercise, the SBP and DBP were not altered. [PERSON] et al. [21] have reported that the BMI of overweight/obese women was not modified after 6 weeks of WBV exercises. Considering the HR (Table 1), an increase was verified in FFG (only 5 Hz) and VFG (variable 5-16 Hz), and this is in agreement with [PERSON] et al. [47] that have also observed an increase of the HR  
Figure 6: Scores of the ESS of the individuals of the group exposed to the intervention with WBV exercises (VFG). in response to exercise. Moreover, [PERSON] et al. [48] have described an association between resting HR and cardiorespiratory fitness with an elevated resting HR. The findings presented in Table 1 indicated no alterations on SBP and DBP due to WBVE (a possible stressor), however, [PERSON] et al. [6] reported that individuals with poor habitual sleep efficiency during the week before stress induction (Trier Social Stress Test) responded with higher stress-related elevations of blood pressure and cortisol levels as compared to subjects with high sleep efficiency. In the current study, no alterations on the NC were found. However, a decrease on the WC was found (Table 1). [PERSON] et al. [49] have compared some anthropometric parameters in trained and sedentary healthy young students. It was found that in moderately aerobic trained students, the BMI and BP were not significantly different between the two groups. However, a significantly lower NC was found in the trained students. Considering the WC, in agreement with our results, [PERSON] et al. [50] have verified that a 12-week supervised aerobic exercise intervention has reduced significantly the WC of overweight/obese men and women. But, [PERSON] et al. [49], have not found alteration in the WC due to exercise. WBV exercise is an intervention with several improvements in populations with various diseases [23; 24; 25; 31]. In this current study, it was verified that WBV exercise has improved the quality of the sleep in MetS when we used the PSQI (Figures 3 and 4) and ESS (Figure 6). This finding is partially in agreement with [PERSON] et al. [51] who have evaluated, in a population of 16 individuals with OSA, the effectiveness of inspiratory muscle training (IMT) on sleep and functional capacity to exercise. It was a significant improvement in sleep quality was seen with PSQI values, but no significant changes were seen in daytime sleepiness (ESS) after the intervention. Furthermore, [PERSON] et al.