INTRODUCTION

The human body is constantly adapting due to the evolutionary process of the species and the impositions of modern civilization’s lifestyle habits, and posture is the result of daily habits adopted throughout life. ¹ When postural changes do not cause immediate pain, they can be neglected and, in the long term, become responsible for muscular adaptations capable of more serious damage to body structures in adulthood. ²

From the age of seven, a child’s posture undergoes a major transformation to achieve a balance compatible with the new body proportions and to meet psychosocial demands . ³ It is in the period from 12 to 14 years for girls and from 14 to 16 years for boys, a phase known as the growth spurt , that there is an increase in height and body proportions, hormonal changes, balance adaptations, and ligament hypermobility. ⁴

Among schoolchildren, the most frequent static postural alterations in the sagittal plane are thoracic hyperkyphosis and lumbar hyperlordosis, characterized by increased curvatures ⁵ , and lumbar and thoracic rectification, characterized by reduced or absent physiological curvatures of the spine ^{6 .} Remaining in a sitting position for long periods with inadequate body positioning ^6,7 , high body mass index (BMI) ⁸ , backpacks carried inappropriately and with excess weight ⁹ , sedentary lifestyle ⁹ , sociocultural factors ¹⁰ , sleeping position ⁷ , emotional characteristics ¹¹ and hereditary burden ³ are associated factors that predispose to the development of postural alterations. Although the growth spurt

phase increases the risk factors for postural alterations, it is also considered an excellent phase for interventions to prevent the onset of postural alterations and diseases associated with these occurrences in adulthood ^7,12 . Identifying postural changes and relating them to their associated factors allows a complete approach to postural changes and their medium and long-term consequences ^7,13 . Given the above, the present study aimed to identify postural changes in the sagittal plane and their possible associated factors in state high school students from the city of Capão da Canoa – RS. METHODS

The school population consisted of 9,504 students from public and private primary and secondary schools, of which eleven were municipal, four were state schools and two were private schools located in the municipality of Capão da Canoa, RS. These data were collected at the 11th Regional Education Coordination Office and the Municipal Education Department of Capão da Canoa. This is a cross-sectional study developed from January to September 2015 and covered a sample of high school students from the state public school system in the municipality of Capão da Canoa, RS. In order to be representative of the municipality, a sample of 157 students was estimated using the G*Power software (version 3.1.9.2), based on a statistical power of 0.90 and a significance level of 5% ¹⁴ . Considering a loss to follow-up of 20%, a minimum sample size of 188 students was required.

Individuals aged between 14 and 19 years for girls and 16 and 19 years for boys who were able to answer the questionnaires were included. Individuals with systemic or neurological diseases, congenital orthopedic disorders, psychiatric disorders, those undergoing physical therapy or orthopedic treatment, and those enrolled in private state schools were excluded. It is important to note that the age range chosen for the study excluded the growth spurt phase for both sexes.

The project met the criteria of the current resolution of the National Health Council on ethics in research involving human beings (nº 466/12) and was approved by the Research Ethics Committee of the University of Santa Cruz do Sul (UNISC) under opinion nº 907.502 of 12/09/14. The informed consent form was signed by the legal guardian and the minor student consent form was signed by the student being evaluated, after providing detailed information about the research procedures. The self-administered Back Pain and Body Posture Evaluation Instrument (BackPEI) ²

questionnaire was used , which consists of 21 closed questions, with the following questions being used: ” Do you feel or have you felt back pain in the last 3 months ?”, ” How often does this back pain occur or occur ?”, ” Has this back pain prevented or prevented you from carrying out activities such as playing, studying and playing sports ?”. This instrument also allowed the anamnesis to be carried out, which was performed on the same day and shift as the other stages of the evaluation of the students. The intensity of back pain in the last 3 months was assessed using the Visual Analogue Scale. To assess individual lifestyle and well-being, a questionnaire adapted from “The Pentacle of Well-Being” ^{15 was used.}

, which consists of closed questions about lifestyle, nutrition, weight control, physical activity, sports activities, behavior, relationships, stress, cultural and leisure activities. The socioeconomic indicators of the adolescent’s family members were assessed through a survey by the Brazilian Association of Research Companies ¹⁶ , which consisted of questions about the family’s assets and the level of education of the head of the family.

To verify body mass, a calibrated portable digital scale (model W801, Wiso Tecnologia Esportiva ^® , Brazil) with a capacity of 180 kg and a graduation of 100 g was used. The height of the sample was assessed using a measuring tape (Wiso Tecnologia Esportiva ^® , Brazil), fixed to the wall and adjusted with a bubble level device to a height of 2.20 m. The individuals were asked to remain barefoot and wear comfortable clothing. The BMI was calculated and classified using the percentile curves recommended by the Center for Disease Control and Prevention according to sex and age ¹⁷ . The weight of the backpacks was measured using a portable digital scale with a properly calibrated capacity of 40 kg (WeiHeng ^® , China), and a backpack weight of up to 10% of the body mass of the student being evaluated was considered adequate.

The postural assessment was performed with the adolescent in an orthostatic position and facing the researcher, with feet parallel, knees extended and 90º of elbow and shoulder flexion. The spinous processes of the C7, T1, T12, L1, L5 and S1 vertebrae were marked and subsequently molded with the Flexicurva (Trident ^® , Brazil), which is a flexible metal ruler measuring 80 cm in length. The Biomec-Flex ^®18 software was used to calculate the angles of the thoracic and lumbar sagittal curvatures. These methods are valid and reproducible for the adult population ¹⁹ and for children and adolescents ²⁰ . The points corresponding to the spinous processes were marked on the flexible ruler, and the outline of the ruler was transcribed onto graph paper containing a Cartesian plane in which x represents the craniocaudal axis and y the anteroposterior axis. In addition to the points corresponding to the spinous processes of the selected vertebrae, six other random markings were made in the spaces of the thoracic and lumbar curvature. These markings generated 18 ordered pairs, which when transcribed into the Software

Biomec-Flex® generated the thoracic and lumbar curvature angles. Subsequently, the values ​​were classified according to the Cobb angle for children and adolescents. Regarding the classification of spinal curvatures in the sagittal plane, normal curvature was considered in the thoracic region as angles of 20º to 50º ²¹ and in the lumbar spine, angles of 31º to 49.5º ²² . Values ​​above 50º in the thoracic region and above 49.5º in the lumbar region represent an increase in physiological curvatures, characterizing thoracic hyperkyphosis and lumbar hyperlordosis, respectively. Values ​​below 20º in the thoracic region and below 31º in the lumbar region represent a reduction in physiological curvatures and characterize thoracic and lumbar rectification ⁷ .

It is important to emphasize that all data collection was performed by a single evaluator, who was an experienced physiotherapist, trained and qualified at the Exercise Research Laboratory of the School of Physical Education, Physiotherapy and Dance of the Federal University of Rio Grande do Sul (ESEFID-UFRGS). The study was blinded only for the measurement of the data obtained. Statistical analysis was performed using SPSS software (Version 22.0, USA), and data normality was assessed using the Kolmogorov Smirnov test and the data expressed as mean, standard deviation and frequency. The association between postural habits, lifestyle, health and well-being and socioeconomic level with postural changes was performed using the Chi-Square and Fisher’s Exact tests (p<0.05). The association between the independent variables and the outcome (presence of postural change) was tested by Poisson Regression, using the prevalence ratio (PR) and 95% confidence interval (CI) values.

RESULTS

The sample consisted of 600 students from the state public school system, of which 363 individuals expressed the desire not to participate in the study and 52 were excluded for missing the research stages. The final sample consisted of 185 eligible students according to the study inclusion criteria (Figure 1). Table 1 presents the anthropometric and sociodemographic characteristics of the sample evaluated.

It was observed that 75 (40.5%) adolescents evaluated presented postural alterations in the sagittal plane and of these, five (2.7%) presented thoracic deviation and 70 (37.9%) lumbar deviation. Regarding thoracic curvature, four (5.3%) presented hyperkyphosis and one (1.3%) presented rectification. Regarding the lumbar spine, two (2.6%) presented hyperlordosis and 68 (90.6%) presented lumbar rectification, and two (5.6%) adolescents presented more than one postural alteration in the sagittal plane.

Tables 2 and 3 show the prevalence of thoracic and lumbar diagnoses stratified by sex, backpack weight and percentile classification, as well as the postural and behavioral habits of the students evaluated. Among the total sample evaluated, 177 (96.2%) had backpacks with adequate weight, with the weight of the backpacks representing 5.89% of the adolescents’ body mass. In the present study, it was possible to identify the prevalence of back pain in 125 schoolchildren (67.60%) (Table 3).

There was an association between the habit of sleeping in the supine position and the presence of lumbar rectification (p=0.014). Regarding socioeconomic class, class C showed a significant association (p=0.048) regarding the tendency to present lumbar rectification, while class B showed a tendency towards postural normality (p=0.019). Of the adolescents belonging to class B, 34.4% presented postural alteration, while among those in class C, 47.16% presented such occurrence (Table 4).

An association was observed between adolescents who carried their backpacks symmetrically (on both shoulders) and the presence of lumbar rectification (p=0.031), highlighting that, of all adolescents with postural changes and who used backpacks with two straps, 128 (69.7%) carried them symmetrically. Males showed a positive association with the presence of lumbar rectification (p<0.001) and thoracic hyperkyphosis (p=0.014). However, the habit of sitting improperly to write and of assuming a sitting position on a bench to talk to friends, to use the computer and to pick up objects from the floor was not associated with the presence of postural changes. Of the students who reported sitting correctly at school, 38.5% presented postural changes, while of those who sat improperly, 39.2% presented postural changes. No association was evidenced between the practice of physical activity and the presence of postural changes (Table 4).

The following positions presented higher prevalence of postural alterations: supine position, inadequate posture for sitting on a bench and for picking up objects from the floor. Inadequate posture and female gender presented lower prevalence when compared to the other categories (Table 5).

DISCUSSION

This study identified postural changes in the sagittal plane and their possible associated factors in high school students from the city of Capão da Canoa – RS. The main results showed a prevalence of 40.5% of postural changes in the sagittal plane, 2.7% in the thoracic spine and 37.9% in the lumbar spine, as well as an association of such changes with lower socioeconomic status, male gender, sleeping in the supine position and symmetrical use of backpacks. A similar prevalence was evidenced by Kunzler et al. ¹³ who identified 20% of thoracic deviations and 37.0% of lumbar deviations after identifying the prevalence of static changes in the sagittal plane and postural habits of 75 students aged 14 to 17 years from the city of Lajeado – RS, using the BackPEI questionnaire and an arcometer to assess spinal curvature. These results differ from those found by Martelli and Traebert ⁵ who found, through individual postural assessment in 344 students aged 10 to 16 years from the city of Tangará – SC, a prevalence of postural alteration of 28.2%, with 11% in the thoracic spine and 20.3% in the lumbar spine.

In the present study, the alteration that presented the highest prevalence was lumbar rectification, which was present in 68 (36.8%) adolescents. In contrast, some authors describe hyperlordosis as the most prevalent alteration, such as Bueno and Rech ²³ , who reported 27.9% of lumbar hyperlordosis and 3.6% of rectification in a sample of 864 students. Similarly, Lemos et al. ²⁴ , in a study with 467 students aged 10 to 16 years from Porto Alegre – RS, found 78.20% of occurrence of lumbar hyperlordosis evidenced by postural assessment with symmetrograph.

There was a higher prevalence of postural alterations among males, with 60% of occurrence, in addition to the association observed between boys and lumbar rectification and thoracic hyperkyphosis. The results obtained by Sedrez et al. ⁷ , when evaluating 59 children and adolescents aged 7 to 18 years from the city of Porto Alegre – RS by means of photogrammetry, evidenced an association between thoracic kyphosis and the female sex. The differences found in the studies cited may be associated with the different age groups studied, which made an adequate comparative analysis between the studies difficult.

Kasten et al. ⁶conducted a systematic review with meta-analysis to identify the prevalence of postural changes in the spine of school-age children and adolescents in Brazil. Although they considered a robust sample size in the analyses of each type of postural change, it was not possible to establish a consensus on the prevalence of anteroposterior and lateral postural changes in the spine. This result may have occurred due to the great heterogeneity of the studies, since they differ greatly in terms of the methods used for postural assessment, sample size, and variability of reference values ​​for the classification of spinal curvatures.

Few studies address socioeconomic aspects and postural changes; however, in our study it was possible to demonstrate a significant association between the presence of postural changes and lower socioeconomic classes (C2). Detsch et al. ²⁵ also found a higher prevalence of postural changes in students from public schools when compared to students from private schools, as well as in students whose parents studied up to elementary school compared to those whose parents studied up to higher education and postgraduate studies. It is suggested that a higher level of education among parents predisposes them to take greater care with their children’s lifestyle habits and posture.

The weight of backpacks and the way they are carried have been a topic of interest and discussion, as this is a risk factor for postural changes. Corroborating this study, Sedrez et al. ²⁶ found that 70.8% of the students evaluated used their backpacks symmetrically. Bueno and Rech ²³ identified that 75.9% of the students evaluated had adequate backpack weights and 80.7% used them symmetrically. In their study, Candotti et al. ²⁷ observed that 80% of the students had backpacks without overloading and 75.9% used them symmetrically. Corroborating the results of the present study regarding the average weight of backpacks of 5.89% of the adolescents’ body mass, Ritter and Souza ²⁸ found backpacks with a percentage of 5.46% of the body mass of elementary school students in Porto Alegre – RS.

As in the present study, the studies cited did not find a significant association between the weight, type or form of carrying of backpacks and the presence of postural changes. On the other hand, Sedrez et al. ⁷ found a significant association between the way the backpack was carried and thoracic and lumbar postural changes, and Nery et al. ²⁹demonstrated a significant association between the weight of backpacks and the presence of scoliosis. In the present study, a significant association was observed between the use of backpacks symmetrically and the presence of lumbar rectification, evidence that contradicts the initial hypothesis that carrying asymmetrically would be related to postural changes. However, Candotti et al. ²⁷ suggest that the lack of adjustment of backpack straps may justify this association, but it is worth noting that this variable was not analyzed in the present study.

Despite the observation of the high prevalence of inadequate postural habits, we did not observe a significant association with the postural changes observed, diverging from the initial hypothesis that daily habits would be related to the presence of postural changes. These data are in line with the study by Sedrez et al. ²⁶ who demonstrated a significant association between the act of picking up objects inappropriately and the presence of thoracic kyphosis, changes in the lumbar region, and the presence of back pain.

The analysis of the position during sleep identified a significant association between the supine position and the presence of lumbar rectification, a finding corroborated by Vasconcelos et al. ³⁰ , who found a higher prevalence of postural changes in those students who reported sleeping in the supine and prone positions, and by Sedrez et al. ²⁶ who found a significant association between posture and the presence of scoliosis. According to Vasconcelos et al. ³⁰ , postural changes may result from the adoption of repeated asymmetrical positions that cause muscular compensations and imbalances. It was not possible to establish the cause for these associations, since the adoption of the supine position is considered adequate, and therefore it is appropriate to suggest further investigations on the type of mattress and pillow used by these adolescents in an attempt to identify the causes of these associations.

In the present study, it was possible to identify a high prevalence of back pain (67.6%), a finding corroborated by several authors ^7,8 . Vasconcelos et al. ³⁰ found a significant association between pain and thoracic hyperkyphosis, however, Sedrez et al. ²⁶demonstrated an association between pain and changes in lumbar lordosis. It is important to emphasize that the finding of different prevalence rates of postural changes among adolescents in school age among the studies evaluated is justified by the methodological differences and age groups evaluated in the various studies, in addition to the local and regional characteristics that impose habits and lifestyles characteristic of each location, making it impossible to compare groups from different cities. In this sense, Kasten et al. ⁶ recommended that macro and microregional differences between states and the country be investigated.

A moderate prevalence of postural changes in the sagittal plane was evidenced, with lumbar rectification being the most prevalent change. It was also found that boys tend to present more postural changes in the sagittal plane, as well as being associated with the presence of lumbar rectification and thoracic hyperkyphosis. An association was found between the presence of postural alteration in the sagittal plane and the use of a backpack symmetrically with lower socioeconomic classes, as well as between the supine sleeping position and lumbar rectification. In this sense, there was a high prevalence of inadequate postural habits adopted daily and back pain.

The present study had limitations that should be highlighted, such as the fact that there is a shortage of studies that used the Flexicurve method in adolescents, which limited the discussion of the data obtained. The adjustments of the backpack straps of the students evaluated were not measured, and this fact may have influenced the association between the use of backpacks with symmetrical straps and the presence of lumbar rectification. The risk of selection bias due to the number of sample losses should be highlighted, in which this fact may have overestimated the prevalence of postural deviation and pain, and the results should be interpreted with caution.

In our study, we found a high prevalence of back pain in the schoolchildren evaluated and a moderate prevalence of postural changes in the sagittal plane, with lumbar rectification being the most prevalent change. It was found that boys tend to present more postural changes in the sagittal plane, as well as being associated with the presence of lumbar rectification and thoracic hyperkyphosis. There was a high prevalence of inadequate postural habits adopted in daily life and back pain, which can be indicated as the associated factors responsible for the postural changes evidenced. These findings can support guidance for health and education professionals regarding possible factors associated with postural changes in school-age adolescents, aiming at the implementation of actions that seek to promote the health of adolescents in order to facilitate the adoption of adequate postural habits and the consequent improvement in quality of life.