Postural alteration, low back pain, and trunk muscle resistance in university students

Introduction: Low back pain, the most prevalent musculoskeletal disorder, is common in individuals with postural changes and has a high incidence in university students. Trunk muscle instability and weakness can contribute to the presence of low back pain. However, no research has investigated the relationship between low back pain in conjunction with postural changes and the resistance of the trunk stabilizing muscles. Objective: To analyze the correlation between postural alterations and muscular resistance of the trunk of women with and without low back pain. Methods: Forty university women were recruited and divided into a group with low back pain (n = 20; 20.85 ± 1.69 years) and a group without low back pain (n = 20; 20.05 ± 2.54 years). On the first day, the postural assessment was carried out by photogrammetry with Kinovea software. On the second day, the resistance tests of the trunk flexor and extensor muscles, lateral and ventral plank, bridge, and lumbar traction were performed through the traction dynamometer. Pearson's correlation test was applied to verify the relationship between the analyzed variables, Student's T test was used for comparison between groups, and a significance level of p < 0.05 was adopted. Results: There was no correlation between the variables related to postural changes and muscle resistance tests (p > 0.05). There was a difference between the groups only for the bridge exercise test (p = 0.04) and vertical alignment of the head, left lateral view (p = 0.041), and right lateral view (p = 0.034). Conclusion: This study did not show a direct and significant relationship between postural changes in young university students with and without complaints of low back pain and resistance of the trunk-stabilizing muscles.


Introduction
Low back pain is considered the most prevalent musculoskeletal disorder. 1 Approximately 80% of people experience lower back pain at least once during their lifetime. 2 Although the main causes of low back pain are mechanopostural or degenerative, 3 such as inflammatory or specific diseases, studies suggest an association between the disorder and the performance of the lumbar musculature, specifically in relation to the resistance of the trunk stabilizing muscles. 4,5 The inability of these muscles to maintain prolonged levels of muscle contraction can have a negative effect on segment stabilization. 6,7 Instability of the posterior column delays nerve conduction, leading to reduced strength of the trunk muscles, which, in turn, can cause pain in the lumbar spine. 8 In university students, studies point to a sedentary lifestyle, 9,10 psychosocial changes, 11,12 trauma 13 and the presence of postural changes [14][15][16] as factors associated with the onset of low back pain episodes. Postural alterations are a consequence of the relative misalignment of different segments of the body; 17, 18 however, body structures tend to seek homeostasis. [19][20][21] Some authors have suggested that when identifying shortened or weak muscles, postural changes can be treated by strengthening and stretching the lumbar muscles. 22,23 Studies have reported a high incidence of postural alterations in university students. Santos et al. 24  Postural changes in university students are associated with class routines, physical inactivity, 25 and sitting postures that are maintained for extended periods, which, as well as compensation and postural changes, generate an overload on the muscles, muscle fatigue and, consequently, compression of blood vessels and nerve endings, culminating in pain mainly in the spine. 18,24,25 Studies have identified, through photogrammetry, postural changes, 14,24,25 related low back pain, [14][15][16] as well as those that could suggest stabilization exercises for patients with low back pain. 22,23 However, no studies have determined the relationship between low back pain and postural changes and resistance of the trunk-stabilizing muscles. Therefore, the objective of this study was to analyze whether there is a relationship between postural changes in young university students with and without complaints of low back pain and resistance of the trunk stabilizing muscles. Therefore, it is hypothesized that women with low back pain will show lower performance in the test of resistance of the stabilizing muscles of the spine and a higher incidence of postural alterations in relation to women without complaints of low back pain and that there will be a correlation between muscular resistance and postural alteration.    Sadler et al. 32 reported that reduced transverse plane control of the hip due to gluteus medius weakness tends to increase femoral internal adduction, rotation, and knee valgus, causing anterior rotation of the ipsilateral pelvis, which alters the load on the lumbar spine and increases the risk of low back pain. In the present study, as no differences were found in performance in the resistance tests of the trunk stabilizer muscles between young people with and without low back pain, it may also justify the absence of significant differences in postural changes.

Discussion
The objective of this study was to identify whether there is a relationship between postural changes in young university students with and without complaints of low back pain and performance of the trunk stabilizing muscles. According to the results, the initial hypothesis of the study was refuted given that in most muscle tests there was no difference between the groups.
Furthermore, no correlation was found between test results and postural changes.

Statistical analysis
Statistical analysis was performed using PASW

Results
The characteristics of the samples are presented in   The data obtained in the present study are important and contribute to greater scientific knowledge about low back pain and postural changes in young people.
However, the eligibility criteria for the low back pain group can be considered a limitation. The occurrence of at least two episodes of nonspecific low back pain in the last three months seemed to be a broad criterion, in which many volunteers fit in even without identifying low back pain as something that impairs functional capacity, allowing them to remain in the tests for longer.
The inclusion of questionnaires that assess the impact of low back pain on daily activities, such as the Roland Morris or Oswestry Disability Index, could contribute to a better characterization of the groups, as well as establish the chronicity of low back pain as a criterion. Another suggestion for future research on the same topic is to include more specific strength and endurance tests for the gluteus medius muscle, given its importance in pelvic stability. 32 Despite continuous investigations and the development of new interventions, musculoskeletal pain in the spine remains a clinical challenge because of its multifactorial nature and high incidence. 38

Conclusion
The data of the present study, under the methodological conditions used, did not show the existence of a direct and significant relationship between postural changes in young university students with and without complaints of low back pain and resistance of the trunk stabilizing muscles. These findings suggest that other musculoskeletal conditions may be involved in differentiating between women with and without low back pain.

Acknowledgment
The present study was financed by the Fundação de

Authors´ contributions
RAF and DHS were responsible for writing the manuscript and, together with MTN, for designing, analyzing, and interpreting the data. All authors approved the final version of the manuscript.