Neck / shoulders pain and its relation to the use of tv / computer / videogame and physical activity in school students from Bauru

Objective: The objective was to determine the prevalence of musculoskeletal pain in the neck/shoulders of school children and its relationship with the level of physical activity and sedentary activities (time spent on TV and computer and/or video game). Materials and methods: We conducted a cross-sectional study with a sample of 524 5th to 8th grade students (278 boys and 246 girls), enrolled in all five urban elementary schools in the municipality of Bauru (SP), aged between 10 and 14 years old. Sociodemographic data, sedentary activities – time spent on TV and computer and/or videogame and level of physical activity was collected through a Physical Activity Questionnaire for Children (PAQ-C). Results: The results showed that the prevalence of localized pain in the neck/shoulders was of 30.1% for boys and girls. It was also found that 1 Support instituition: CNPq.


Introduction
The neck/shoulders pains are common among school students, with a yearly prevalence varying from 7% to 58% (1, 2).These symptoms have increased in recent decades and the knowledge on its causes is little.Some authors suggest that the main risk factors are biological, mechanical and cognitive, highlighting: sex, obesity, a decrease on the flexibility and mobility of muscles, hypermobility, depression, school level, competition sports, type and way of carrying and transporting weight, posture habits, domestic and occupational ergonomic factors, sedentary activities (time spent on TV and computer/ videogame), physical activity level and smoking (3,4).
Cross-sectional investigations have pointed that the time spent watching television and using the videogame is positively related to musculoskeletal pain (4,5,6).
Data on the association between the level of physical activity and musculoskeletal pain is contradictory.Some studies show a relation between a low level of physical activity and neck/shoulders pain (7,8,9), while others (10,11,12,13,14,15,16) do not report an association between physical activity and neck/ shoulders pain among school students.
The relevance of studies on the prevalence of musculoskeletal symptoms in the spine among school students lies in the fact that these pathologies generate economical and social consequences to both the State and the individuals.To the individual, it means a loss in quality of life and to the State, costs with treatment and rehabilitation (17).
Thus, taking into account 5th to 8th grade elementary school students from Bauru, this study aimed at verifying the prevalence of neck/shoulders musculoskeletal pain among school students and its relation to the level of physical activities and sedentary activities (time spent on TV and computer and/or videogame).

Materials and methods
This cross-sectional study was carried out in 2009 with a population of 5th to 8th grade school students Neck/shoulders pain and its relation to the use of tv/computer/videogame and physical activity in school students from Bauru 113 or videogame) were collected through the questionnaire (18,19), which consisted of the following questions: age (10, 11, 12, 13 and 14 years old); sex; "In a normal school week, do you watch TV?" (yes/no); "In a normal school week, how many times do you watch TV?" (once, twice, three times, four times, five times or more a week); "In a normal school day, how many hours do you watch TV for?" ( less than an hour, two hours, three hours, four hours, five hours or more a day); "In a normal school week, how many times do you use the computer or the videogame at home ?" (once, twice, three times, four times, five times or more a week); "In a normal school day, how many hours do you use the videogame at home for?" ( less than an hour, two hours, three hours, four hours, five hours or more a day).
The level of regular physical activity was evaluated by the Physical Activity Questionnaire for Children (PAQ-C), which was translated and adapted only in order to exclude the sports and physical activities not practiced in Brazil (20,21).Such instrument consists of nine questions on the practice of sports and games, physical activities at school and on leisure time, including the weekend.Each questionnaire item is scored on a 5-point scale and the final score is obtained by the mean of the questions, representing the interval from very sedentary (1) to very active (5).The scores 2, 3 and 4 indicate the categories sedentary, moderately active and active, respectively.So, it´s possible to classify the subjects as active or sedentary based on this score.The active are the ones with a score ≥ 3 while the sedentary are the ones with a score < 3.
The score mentioned above had to be changed for question 1, which is composed of a list of activities, by the division of the total score obtained in the question by the number of activities in the list, including also the activities that had been added in the section "others".
The same kind of procedure was necessary for question 13, which indicates the level of physical activity in each weekday.This question total score was divided by 7. The final score is obtained by the mean of the questions 1 to 7, 9 and 13.
The variables (sedentary activities -time spent on TV and computer and/or videogame and level of physical activity) were considered as independents.
The dependent variable -neck/shoulders painwas observed through the Nordic Questionnaire, which was adapted to the Brazilian culture by Barros (22).The pain was defined as pain or discomfort enrolled in all five municipal urban elementary schools of Bauru (SP), aged between 10 and 14 years old.
The sampling process was carried out through a multi-stage technique (18): first, a stratified sample proportional to the number of students of each school was performed, followed by a random sample inside each school.This sampling process allowed that each school student had an equal probability of being randomly chosen.
The sample size to evaluate the prevalence of neck/shoulders musculoskeletal symptoms was calculated from a population of 1505 students enrolled in the five elementary schools.This analysis adopted a prevalence of 50% (unknown prevalence), an acceptable error of four percentage points, a confidence level of 95% and a design effect of 1.5.A total of 524 students was estimated considering these points.
The criteria adopted in order to exclude some school student who was randomly chosen to take part in the study were: younger than 10 years old and older than 14 years old; failure to hand in the Informed Consent Form (ICF) signed by the parents/ responsible ones; and refusal to take part.

Procedures
The city Education Department (Secretaria de Educação) issued a letter of authorization.The students' parents were informed on the ethical aspects and signed the informed consent form.The Project was approved by the Research Ethics Committee at Universidade Sagrado Coração (proc.10/07).
The data collection was carried out from February to May in 2009, with the collaboration of each class professor, who sent one student a time to answer the questionnaire.The study objectives were explained to each student, then, the researcher carried out the structured interview, question by question.Each individual approach lasted about thirty minutes.
The team in charge of data collection consisted of two researchers trained based on a standardized data collection protocol (theoretical and practical), which had been previously established to minimize possible errors intra-and inter-evaluators.The technical error of measurement was not determined by the collection team, but the sample of school students was measured in duplicate to control the quality of the questionnaires.
The variables (age, sex, school grade and sedentary activities -time spent on TV and computer and/ level of 5% and a confidence interval (CI) of 95% were considered with the calculation of adjusted odds ratios (18).

Results
From the 536 students evaluated, 12 (2.3%) were excluded as they didn´t have the appropriate age for the studied grades.So, the sample consisted of 524 students distributed in 278 boys (53.1%) and 246 (46.9%) girls.
It is possible to observe in Table 1 that, in both sexes, there was a greater prevalence of sedentary school students who watch TV and use the computer for more than three hours a day, with a frequency over three times a week for both.
The prevalence of pain located in the neck/shoulders was of 31.1% of the total of school students verified; the prevalence was of 30.2% in boys and 32.1% in girls.
Table 2 shows that the factors associated with the symptoms reported in the neck/shoulders, in boys, were the frequency and amount of hours a day watching TV and hours on the computer.
Regarding the girls, Table 3 shows that there was an association between the pains located in the neck/ shoulders and the frequency and amount of hours a day watching TV.
in the last twelve months, not related to trauma or menstrual pain.
The following question was asked to the school students in the moment of the interview: "Have you had neck/shoulders pain in the last year?".For a greater specificity on the pain location, besides the verbal questioning, an image of the neck/shoulders area in different colors was presented so that they could identify the areas.This kind of tool is valid and reliable to measure pain among school students, as it enables the students to be very specific about the pain location.

Analysis of results
Data was inserted in a database and the analysis was carried out stratified by sex using the statistical software SPPP, version 10.0 (SPSS Inc., Chicago, United States).The analysis was carried out following a descriptive approach and another analytical one.
In the descriptive approach, the distribution of absolute and relative frequencies was made for the categorical variables.In the analytical approach, a bivariate analysis was carried out through the Pearson test and, then, a multivariate binary logistic regression was carried out following a hierarchical model.The method adopted for introducing the variables in the models was the backward stepwise.A significance

Discussion
The results of this study show that the prevalence of pain in the neck/shoulders (31.1%) is, in general, similar to the rates recorded in the literature, which vary from 13% to 34.5%, as it can be demonstrated in the percentages found in some studies on neck/ shoulders pain: 11.5% of the Dutch students reported such pain (2), 21% of the Finnish (4) and 28.5% of the Western Australia residents (23).
These variations in the symptoms reports may be related to the definition of cervical/neck pain, the differences between populations, the exposure time factor and psychological factors (19).
In this study, the multivariate analysis showed that there was an association between the use of computer and television and the neck/shoulders pain in both sexes.In a study with Finnish adolescents (9), the risk of pain was of 1.30 among the school students who stay in front of TV and computer for over two hours, while among the Spanish (24) and the Nigerian (25) students, the risk was of 1.5 and 2.0, respectively, for the ones who used the computer for more than two hours.Another study did not find any association between these variables (2).This association can be motivated due to the extended time sitting and/or to an incorrect posture, inappropriate and poorly organized furniture.The sitting posture generates many alterations in the musculoskeletal structures of several body segments: it increases by 35 %, approximately, the internal pressure in the nucleus of the intervertebral disc , it stretches all the spine structures (ligaments, nerves and small joints), it decreases the return circulation of inferior limbs and causes the development of inflammatory processes in the osteomuscular structures with associated painful symptoms (26).
No association between the level of physical activity and pain was found in this study, confirming the results of other investigations (27,28).Other researches also didn´t find any association between the neck / shoulders pain and physical activity (10,11,12,13).
The limitations must also be considered.The measurements were based on self reports and collected in a short period of time.Due to confidentiality, data relating to symptoms, practice of sports, frequency and hours spent on TV/computer which were answered by the students was not researched with the family members.In some cases, it might have happened, mainly regarding the symptoms, a difficulty for the teenagers to remember the presence or absence of the same after twelve months.However, the Nordic Musculoskeletical Questionnaire agrees with a clinic evaluation (27) and the self-reported data on physical activity are similar to this variable objective measures (29).
Taking into account its cross-sectional design, it is not possible to infer any causality in this study, only an association.Consequently, this study does not allow us to judge if any characteristic of an activity is mediated by a neck/shoulders pain experience.It is possible that adolescents who have pain avoid activities that can propagate it, which eliminates any association in a cross-sectional analysis.Therefore, a prospective study will be important to investigate the association between pains and physical activity and use of TV/computer and take into account other factors that mediate such associations in order to determine with certainty such risks regarding the pains.Prospective data suggests that the natural course of the neck/shoulders pain varies throughout life, but the same kept on for a small subgroup of adolescents.A detailed exam in this subgroup or in another one without any particular comorbidities may contribute to elucidating the association between the pains and the studied variables (30).

Conclusion
The results showed that there is a predominance in the manifestation of symptoms reported in the neck/shoulders, in boys, regarding the frequency and amount of hours a day watching TV and amount of hours on the computer while, among the girls, the association was with the frequency and amount of hours a day watching TV.A highly favorable point of this study was the use of validated questionnaires for the Brazilian population (Nordic Questionnaire and PAQ-C), as well as the data having been collected from adolescents with the same socioeconomic level and the analysis having been carried out stratified by sex.A significant contribution is that this kind of data, and others resulting from it, may improve the understanding of the relations between the variables and offer useful elements to the implementation of measures aiming at the maintenance, improvement and promotion of the students' psychological and physical well-being (19).

Table 1 -
Distribution of absolute and relative frequencies of sedentary activities and level of physical activity according to sex, Bauru -2009 /shoulders pain and its relation to the use of tv/computer/videogame and physical activity in school students from Bauru 115 Source: Research data.Neck

Table 2 -
Result of the multivariate binary logistic regression, final model for independent associations with pain in the neck/shoulders among male school students,Bauru -2009

Table 3 -
Result of the logistic regression multivariate analysis, final model for independent associations with pain in the neck/shoulders among female school students,Bauru -2009