## 3 Results  
A total of 177 publications were identified through the database search (PubMed, Embase, Web of Science, and Scopus), and one article was included through other sources. Thirty-eight duplicate articles were excluded, leaving 140 articles for screening. During screening, 116 publications were excluded because they were not related to the subject of the current review, and 24 were considered for eligibility. After analysis, a further 19 articles were excluded. Finally, 5 articles were included in this systematic review. A flowchart according to PRISMA is presented to highlight the steps for selecting the full articles analyzed in the current systematic review (Figure 1). Table 1 presents the characteristics of each study related to the type of publication, demographics, aims, results, and level of evidence of the selected publications. Among the five studies included, there were two experimental studies [29; 30] with a III-2 level of evidence and three cross-sectional studies [2; 31; 32] with a III-3 level of evidence. The number of individuals in the included publications ranged from 7 to 760 participants of both sexes (men and women). The aims in the three studies [29; 31; 32] were focused on the prevalence of LBP, and two [2; 30] focused on the level of exposure to vibration. The results showed that four studies reported an association between vibration and LBP [2; 29; 30; 32] and one study did not report this association [31]. The variables evaluated in the studies were WBV, bus model, seat model, vibration measurement, and exposure time. The reported bus models varied between old buses, new buses, low-floor buses, and high-floor buses. The different models also varied according to  
Figure 1: PRISMA flow diagram of the literature selection process. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**Study** & **Study Design** & **Demographics** & **Aim** & **Results** & **LE** \\ \hline \hline  & & 234 drivers (male) & To analyze the prevalence of & The findings also indicated that among bus & & \\ [PERSON] et al., 1992 & Experimental study & Age: 41.2 years & Age: 41.2 years & severe types of LBP among & drivers, lumbar symptoms occurred at levels of & \\  & & 125 control workers & bus drivers employed in a & exposure to W8P below the health exposure & III-2 \\  & & Age: 44.5 years & municipal public transport & limits proposed by the International Standard & \\  & & Age: 44.5 years & company: & & \\ \hline  & & & To determine the prevalence & This study revealed no significant association & \\ [PERSON] et al., 2007 & Cross-section of a cohort study & 760 drivers (male) from 11 bus & of musculoskeletal disorders, including LBP and reveal the & between W8P exercise and LBP and & \\  & & & & & demonstrated that the risk factors for & III-3 \\  & & & physical and psychological & developing LBP or not depend on just one & \\  & & & risk factors. & & factor (physical and psychological). & \\ \hline  & & & & & \\  & & & & & \\ \multirow{4}{*}{[PERSON] et al., 2007} & \multirow{4}{*}{Cross-sectional study} & 61 drivers (58 men and 3 women), & To investigate the typical & & \\  & Age: 19 to 64 years & exposures of urban bus & or unsupported, perform occasional and light & \\  & & Body mass: between & drivers to the demands of & & \\  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \hline  & & Low floor: 15 drivers (13 men & & WB exposures were significantly different & \\  & & and 2 women) & & & & \\ \cline{1-1}  & & Mean age: 42.3; Mean body mass: & To determine if there are & between road types, both hip-floor and & \\  & & & 93.7 kg Menon height: 176.8m; & differences in performance & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & Mean BMI: 300 kg/m\({}^{2}\): High & road and the traffic & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}