The aim of the study was to evaluate the association between strength, flexibility, and musculoskeletal pain in university staff members over the course of two years. Our main findings show significant loss of strength and flexibility over time. As for pain, there was a variation of approximately 4%, being that 62.2% of individuals presented some pain in the follow-up, with a higher frequency in the back, neck, shoulders, arms and hands regions. When the strength of individuals was associated to the presence or absence of pain, the results showed that the individuals with less strength at baseline (Percentile<75) presented a 3.2 higher chance of pain 2 years later and for individuals with the worst classification of strength in the follow-up, the chance increased up to 5.6.
When compared to existing literature, our study shows higher strength loss percentages than other demographic groups (elderly and adults without sedentary professions) (Figure 4). Strength loss over the years is a natural process. People reach peak muscular mass near the age of 25 and from age 45 on, the decline becomes more evident [27]. Some studies showed lower strength loss values than the presented study [28–33]. However, the group of people from previous studies were composed by older adults, which limits comparisons. This can be explained by the sedentary nature of the work of the individuals. Spending many hours in sedentary behavior is inversely associated with muscular strength and percentage of lean mass [34], and is characterized by the disuse syndrome [18, 31]. Another possible factor that explains higher strength loss values than the studies with elderly populations, is that individuals with higher strength values at the baseline, when not perfoming physical exercise, present higher values of strength loss[31].
When the subjects were separated in groups by lumbar traction strength, the weakest presented 3.2 times more of a chance of presenting pain in the future and the value is 5.6 times higher when the analysis is transversal, if compared to the strongest participants. Weber et al. [35] found similar results of the present study, in transversal analysis, in which the lowest quartiles showed an exposure for musculoskeletal pain (OR: 3.47; 1.27 – 9.49). Also, the reported study showed the intensity of pain felt, noting a pattern in the sensitivity as the values are moderate for all spots. The extensor muscles of the lumbar spine are responsible for the stability of the spine and consequently to prevent injury, however the atrophy of these muscles can generate localized chronic pain [36, 37]. However, there is evidence that physical exercise programs that improve strength in people with musculoskeletal pain in the lumbar region, also result in a lower number of individuals with pain post-intervention [38].
When the pain location was evaluated, the regions that presented a higher increase in pain frequency were the neck, back, shoulder and hand regions. Scarabottolo et al. [39], found higher pain prevalence in the neck region in adolescents physically inactive and concluded that an occupational activity can be a factor of risk for pain. This fact is justified by the fact that sedentary activities and sitting positions increase the static contraction time of the regions that promote body stabilization (neck, shoulder, and back), causing an overload and increased muscle fatigue, resulting in musculoskeletal pain [14, 40]. The study demonstrates the presence of skeletal muscle pain in 62.3% of participants and an incidence of painful symptomatology of 4%. These results can be justified by the studies mentioned above and the fact that this group of people can last up to 12 hours in sedentary behavior [16].
Although the participants showed a decrease in flexibility values over the years, this study did not find significant associations between flexibility evaluated by sit-and-reach test and musculoskeletal pain, in neither transversal or longitudinal associations. Battie et al. [41], found that flexibility is not associated with lumbar pain in industrial workers, besides, the workers with lumbar pain history presented lower values of flexibility. Although, a possible explanation for the flexibility results without significant, is due to the characteristic of the sit-and-reach test, who didn’t assess flexibility in other regions; the test is good to measure hamstring and lumbar flexibility, but can’t be generalized [42]. Also, the spots with a higher prevalence of pain in follow-up (neck; shoulder; arms; hands; back) have not evaluated by flexibility with the sit-and-reach test.
The strength of this study can be related to the fact that the study has a longitudinal character. The study also increases in the explanation of associated factors of muscular pain, and it presents percentages of muscle strength loss for university workers, a population that development functions in hospitals, administration of public services, research, and security. However, the limitations of the study are due to high sample loss. Besides, the characteristic of the sample was kept, once the individuals that were lost were equal to the ones who followed, this fact was confirmed when compared the values of characterization (body mass; body mass index; strength and flexibility) of the individuals that didn’t remain in the research and their pairs. Also, a analysis without stratified for the genders, and the evaluation of flexibility in only one body region, were included as a limitation.
In accordance to the information presented above, it can be concluded that university staff members with a predominantly sedentary profession, present high rates of musculoskeletal pain, mainly in the trunk regions (lumbar, back, shoulders and neck). Thus, these workers have high rates of strength loss and flexibility. In addition, muscle strength can predict painful symptomology even after 2 years.