Development and validation of a questionnaire measuring factors associated with physical activity in adolescents

Psychosocial mediators and moderators of a school-based physical activity intervention among Brazilian adolescents

School-based interventions are needed due to the low levels of physical activity (PA) in adolescents. The aim is to examine the mediation effects of psychosocial factors (attitude, self-efficacy, social support from parents, friends, general teachers, and PE teachers, and environment school perception) and moderation by sex, school grade, and socioeconomic level of a school-based PA intervention on the PA practice among adolescents. The Movimente Programme is a randomised controlled trial at schools in southern Brazil (n = 921 adolescents). Strategies included teacher training, educational actions, and environmental changes. Adolescents self-reported their weekly PA. Potential psychosocial mediators and moderators were investigated through validated questionnaires in a Brazilian sample. The product of the coefficients with percentile bootstrapping 95% confidence interval was performed. The Movimente Programme was related to positive changes in adolescents' perception of the school environment and social support from general and physical education teachers. Most psychosocial variables (attitude, self-efficacy, social support from friends, and social support from teachers) were associated with PA, but none mediated the impact of the Movimente Programme on PA. Results varied according to sex and school grade. The Movimente Programme increased the adolescents' perception of the school environment and social support from teachers, but no mediators were confirmed.

[Reproducibility, validity and internal consistency of the environment scale for physical activity of adolescents]

The objective was to analyze the reproducibility, validity and internal consistency of the environment scale for the physical activity in adolescents. Reproducibility study with 171 adolescents (59.5% female); and validity and internal consistency with 1.353 adolescents (53.1% female). The scale contained 25 items in three domains: places of practice (PP - 14 items); urban security (US - six items) and; in transit (TS - five items). Kappa PABAK and Spearman correlation (rho) were used to assess reproducibility, exploratory factor analysis (EFA) and confirmatory (CFA) for validity, the combined reliability index (CRI) for internal consistency. The reproducibility of the scores was PP - rho = 0.76; US - rho = 0.78 and; TS - rho = 0.66. Three factors were identified in the EFA: PP (eight items, factorial loads from 0.36 to 0.67); US (four items, factorial loads from 0.60 to 0.78) e; TS (four items, factorial loads from 0.35 to 0.64). The CFA confirmed the model with three factors and with levels recommended for the fit quality indicators of the model. The internal consistency was satisfactory for PP (CRI = 0.85), US (CRI = 0.90) and TS (CRI = 0.79). The environment scale for the practice of physical activity showed adequate levels of reproducibility, construct validity and internal consistency.

Peer-led physical activity intervention for girls aged 13 to 14 years: PLAN-A cluster RCT

Background

Increasing physical activity among girls is a public health priority. Peers play a central role in influencing adolescent behaviour. Peer-led interventions may increase physical activity in adolescent girls, and a feasibility trial had shown that PLAN-A (Peer-led physical Activity iNtervention for Adolescent girls) had evidence of promise to increase physical activity in adolescent girls.

Objective

The objective was to test whether or not PLAN-A can increase adolescent girls’ physical activity, relative to usual practice, and be cost-effective.

Design

This was a two-arm, cluster-randomised controlled trial, including an economic evaluation and a process evaluation.

Participants

State-funded secondary schools in the UK with girls in Year 9 (aged 13–14 years) participated in the trial. All Year 9 girls in participating schools were eligible.

Randomisation

Schools were the unit of allocation. They were randomised by an independent statistician, who was blinded to school identities, to the control or intervention arm, stratified by region and the England Index of Multiple Deprivation score.

Intervention

The intervention comprised peer nomination (i.e. identification of influential girls), train the trainers (i.e. training the instructors who delivered the intervention), peer supporter training (i.e. training the peer-nominated girls in techniques and strategies underpinned by motivational theory to support peer physical activity increases) and a 10-week diffusion period.

Outcomes

The primary outcome was accelerometer-assessed mean weekday minutes of moderate to vigorous physical activity among Year 9 girls. The follow-up measures were conducted 5–6 months after the 10-week intervention, when the girls were in Year 10 (which was also 12 months after the baseline measures). Analysis used a multivariable, mixed-effects, linear regression model on an intention-to-treat basis. Secondary outcomes included weekend moderate to vigorous physical activity, and weekday and weekend sedentary time. Intervention delivery costs were calculated for the economic evaluation.

Results

A total of 33 schools were approached; 20 schools and 1558 pupils consented. Pupils in the intervention arm had higher Index of Multiple Deprivation scores than pupils in the control arm. The numbers randomised were as follows: 10 schools (n = 758 pupils) were randomised to the intervention arm and 10 schools (n = 800 pupils) were randomised to the control arm. For analysis, a total of 1219 pupils provided valid weekday accelerometer data at both time points (intervention, n = 602; control, n = 617). The mean weekday moderate to vigorous physical activity was similar between groups at follow-up. The central estimate of time spent engaging in moderate to vigorous physical activity was 2.84 minutes lower in the intervention arm than in the control arm, after adjustment for baseline mean weekday moderate to vigorous physical activity, the number of valid days of data and the stratification variables; however, this difference was not statistically significant (95% confidence interval –5.94 to 0.25; p = 0.071). There were no between-arm differences in the secondary outcomes. The intervention costs ranged from £20.85 to £48.86 per pupil, with an average cost of £31.16.

Harms

None.

Limitations

The trial was limited to south-west England.

Conclusions

There was no evidence that PLAN-A increased physical activity in Year 9 girls compared with usual practice and, consequently, it was not cost-effective.

Future work

Future work should evaluate the utility of whole-school approaches to promote physical activity in schools.

Trial registration

This trial is registered as ISRCTN14539759.

Funding

This project was funded by the National Institute for Health Research (NIHR) Public Health Research programme and will be published in full in Public Health Research; Vol. 10, No. 6. See the NIHR Journals Library website for further project information. This trial was designed and delivered in collaboration with the Bristol Randomised Trials Collaboration (BRTC), a United Kingdom Clinical Research Commission (UKCRC)-registered Clinical Trials Unit that, as part of the Bristol Trials Centre, is in receipt of NIHR Clinical Trials Unit support funding. The sponsor of this trial was University of Bristol, Research and Enterprise Development www.bristol.ac.uk/red/. The costs of delivering the intervention were funded by Sport England.

[Does nutritional status moderate the association between social support, self-efficacy, and physical activity time of adolescents?]

The scope of this paper is to analyze the association between social support, self-efficacy and practice time of physical activity of different intensity (light, moderate, vigorous) and evaluate if these associations are moderated by the nutritional status of adolescents. It involved a cross-sectional study with 650 adolescents (10-14 years old, 52.9% female) from João Pessoa, State of Paraíba. Social support was measured by a scale with five items for each source of support (father, mother and friends) and self-efficacy, with a scale of four items. The physical activity time was measured by means of an accelerometer and the nutritional status was assessed by body mass index. The results of the multiple linear regression analysis showed that social support of friends was positively and significantly associated with moderate intensity physical activity time (β=2.67; CI95%: 0.28; 5.07). The nutritional status did not moderate the association of social support and self-efficacy with the duration of physical activity (p>0.05). The conclusion drawn is that adolescents who perceived that they are receiving more social support from friends tend to practice more moderate intensity physical activity, irrespective of their nutritional status.

Reliability, validity and internal consistency of social support and self-efficacy scales for physical activity in adolescents with 10 to 14 years of age

Objective:

To analyze the reliability, validity and internal consistency of the physical activity social support (SSS) and self-efficacy (SES) scales among adolescents aged 10–14 years.

Methods:

The reliability study included 171 adolescents (mean age=12.3±1.0 years, 59.6% female) and validity and consistency study with 1,107 (mean age=12.0±1.0 years, 52.7% female). The SSS had 15 items and the SES eight items. Reliability was determined by Spearman's correlation analysis (rho) and validity and internal consistency by factor analysis (exploratory — EFA and confirmatory — CFA) and the composite reliability (CR), respectively.

Results:

The reliability of SSS (father: rho=0.80; p<0.001 | mother: rho=0.76; p<0.001 | friends: rho=0.75; p<0.001) and SES (rho=0.72; p<0.001) were considered high. In the EFA, three factors were identified for the SSS (father, mother and friends — five items each) and one factor for SES (five items), confirmed in the CFA. Quality parameters of adjustment in the final models were satisfactory for SSS (chi-square=240.5 [p<0.001]; root mean square residual — RMR=0.05; root mean square error of approximation — RMSEA=0.04 [90%CI 0.04–0.05]; goodness of fit index — GFI=0.97; adjusted goodness of fit index — AGFI=0.96 and comparative fit index — CFI=0.97) and SES (chi-square=5.4 [p=0.07]; RMR=0.01; RMSEA=0.04 [90%CI 0.00–0.08]; GFI=0.99; AGFI=0.99 and CFI=0.97). Internal consistency was considered satisfactory for SSS (CR: father=0.79, mother=0.77, friends=0.78) and low for SES (CR=0.38).

Conclusions:

The scales showed satisfactory levels of reliability and of construct validity. However, only the SSS showed adequate levels of internal consistency.%

Daily activity limitations and physical activity encouragement influence adolescents seeking health care for neck and low back pain

BACKGROUND

Understanding the factors associated with care-seeking behaviour in adolescents with spinal pain will inform health care professionals and guide a better decision-making.

OBJECTIVE

To identify factors, including parents' habits and behaviour, related to care-seeking in adolescents with neck pain or low back pain (LBP).

STUDY DESIGN

A cross-sectional study.

METHODS

Adolescents between 10 and 17 years were randomly recruited from public schools. The proportion of adolescents with neck or LBP and those who had sought care for neck and LBP were assessed with the Nordic Musculoskeletal questionnaire. Daily activity limitation and the frequency of parents' habits and behaviour were collected using self-reported questions. Logistic regression analyses were performed to investigate if the following factors were associated with adolescents' care-seeking behaviour due to neck or LBP: daily activity limitations, physical activity (PA) domains, items of the social support scale.

RESULTS

The prevalence of adolescents reporting neck or LBP was 31.4% (318 out of 1011). Of these, 35.8% (n = 114) sought care for neck or low back pain. Activity limitations related to neck or LBP (OR: 5.83, 95% CI: 3.46 to 9.84), higher PA levels at school (OR: 1.67, 95% CI: 1.02 to 2.75), and PA encouragement (OR: 2.73, 95% CI: 1.27 to 5.85) were associated with care-seeking in adolescents with neck or LBP.

CONCLUSION

Adolescents with activity limitations due to neck or LBP, higher PA levels at school and encouraged by parents or friends to practice PA were more likely to seek care for their neck or LBP.

[Interaction of sociodemographic factors in the association between psychosocial factors and active commuting to school]

The study aimed to analyze the interaction of sociodemographic factors in the association between psychosocial factors and active commuting to school. This was a cross-sectional study in 2018 with a sample of 1,984 students. The target sociodemographic factors were sex, age, parents' schooling, and socioeconomic status. Social support and self-efficacy were measured with questionnaires. Active commuting to school was defined as walking, bicycling, or skateboarding to and from school. Binary logistic regression was used to verify the association between psychosocial factors and active commuting to school. Then, interaction terms with the sociodemographic variables (age, father's schooling, mother's schooling, socioeconomic status) were included in the relationship between psychosocial factors and active commuting to school. The sample consisted of 1,984 adolescents (55.9% females). Of these, 748 (37.7% of the sample) reported active commuting to school during a normal week. Analyses of interaction showed that high levels of schooling and high socioeconomic status were negatively associated with active commuting to school. Low socioeconomic status and low schooling were positively associated with such commuting. The peer social support scale showed more significant variables than the other scales. The results indicate that sociodemographic factors (parents' schooling and socioeconomic status) moderate the association between psychosocial factors and active commuting to school.

Protocol paper for the Movimente school-based program: A cluster-randomized controlled trial targeting physical activity and sedentary behavior among Brazilian adolescents

BACKGROUND

A better understanding of how multicomponent school-based interventions work and their effects on health and education outcomes are needed. This paper described the methods of the Movimente Program, a school-based intervention that aims to increase physical activity (PA) and decrease sedentary behavior (SB) among Brazilian students.

METHODS

This is a cluster randomized controlled trial with adolescents from 7th to 9th grade in public schools from Florianopolis, Southern Brazil. After agreement, 6 schools were randomly selected to intervention or control groups (3 schools each), and all eligible students were invited to the study. The Movimente intervention program was performed during a school year and included 3 main components: Teacher training (including face-to-face meeting, social media platform, and handbook with lesson plans); improvements in the PA environment in school; and educational strategies. Control schools continued with their traditional schedule. Baseline (March/April 2017), postintervention (November/December 2017), and maintenance (June/July 2018) evaluations included PA and SB as primary outcomes (assessed by self-report and accelerometry). Secondary outcomes included psychosocial factors related to PA and SB (e.g., social support and self-efficacy), as well as health (e.g., quality of life and nutritional status) and education (e.g., academic achievement) outcomes. A program evaluation was performed based on the RE-AIM framework. Participants, intervention staffs, and evaluators were not blinded to group assignment, but a standardized evaluation protocol was applied independently of the trial allocation.

RESULTS

Statistical analyses will include a multilevel approach for repeated measurements and mediation analysis. Any side effects of the intervention will be recorded. The sample size close to that expected (n = 1090) was reached (n = 999). The results of this trial will involve valuable information about the effect and the evaluation of a multicomponent intervention carried out in a middle-income country.

CONCLUSION

By creating opportunities for adolescents to be active at school using multicomponent strategies, the Movimente program has the potential to enhance students health and academic performance which may encourage the school community (e.g., teachers, principals) to adopt the program. Also, this trial will provide evidence for practitioners, policy makers, and researchers on how multicomponent program may be implemented in a school setting.

TRIAL REGISTRATION

The trial is registered at the Clinical Trial Registry (Trial ID: NCT02944318; date of registration: 18 October 2016).

Nível insuficiente de atividade física e elevado tempo de tela em adolescentes: impacto de fatores associados

Resumo Verificar o impacto de fatores associados ao nível insuficiente de atividade física e elevado tempo de tela em adolescentes. Estudo transversal, representativo, com 899 alunos de ensino médio da rede pública de São José dos Pinhais, Paraná, Brasil. Foram mensurados o nível de atividade física e o tempo de tela e classificados respectivamente de acordo com as recomendações da Organização Mundial da Saúde e da American Academy of Pediatrics. Os fatores associados para o nível insuficiente de atividade física e tempo de tela foram: sexo, maturação sexual, apoio social e autoeficacia para a prática de atividade física. As associações foram testadas com a regressão de Poisson. E o impacto dos fatores associados ao nível insuficiente de atividade física e do elevado tempo de tela foram calculadas pela fração atribuível populacional (FAP) e a redução relativa do risco (RRR). Na presença combinada do nível insuficiente de atividades físicas com o elevado tempo de tela, o sexo feminino apresentou uma FAP = 13,04, o estágio pós-púbere FAP = 9,91 e o apoio social apresentou uma RRR = 31,00. Os achados sugerem sexo feminino e estar no estágio pós-púbere como fatores de risco, e apoio social como fator protetor a presença combinada do nível insuficiente de atividade física e do elevado tempo de tela.

CORRELATES OF PHYSICAL ACTIVITY IN ADOLESCENTS OF PUBLIC SCHOOLS IN CURITIBA, PARANÁ, BRAZIL

Objective:

To verify the association of nutritional status, biological maturation, social support and self-efficacy with the physical activity level of 2,347 students of both sexes, aged between 11 and 15 years old, enrolled in state schools in the city of Curitiba, Paraná, Brazil.

Methods:

Anthropometric measurements of body mass, height and sitting height were collected. The assessment of biological maturation was based on the analysis of the age at peak height and sexual maturity. The physical activity level, social support from parents and friends and self-efficacy were evaluated by self-reported questionnaires. Sex/age-specific body mass index (BMI) cutoff points identified the nutritional status. Gross and adjusted binary logistic regression were used to obtain odds (OR) ratios with 95% confidence intervals (95%CI), adopting p≤0.05 as significant.

Results:

More than half (52.3%; n=1,227) of students were active, with boys in a higher proportion (64.1%; p≤0.01). The correlates of physical activity were: nutritional status (OR 1.25; 95%CI 1.01-1.56), early somatic maturation (OR 0.71; 95%CI 0.54-0.93), moderate (OR 1.85; 95%CI 1.50-2.30) and high social support from parents (OR 2.70; 95%CI 2.11-3.42) and high social support from friends (OR 1.78; 95%CI 1.42-2.24).

Conclusions:

Nutritional status, early somatic maturation, social support of parents and friends were correlates of physical activity. Overweight girls with moderate and high parental support and boys with greater social support from parents and friends were more active. Girls with early somatic maturation were less active.

Is the association between sociodemographic variables and physical activity levels in adolescents mediated by social support and self-efficacy?

OBJECTIVE

Analyze whether the association between sociodemographic variables and physical activity levels is mediated by psychosocial factors.

METHODS

This is a cross-sectional epidemiological study of public and private high school students in João Pessoa, Paraíba state, Brazil. A total of 2540 adolescents (57.0% female) were analyzed (16.4±1.2 years). Physical activity was estimated using a questionnaire, self-efficacy, and parents' and friends' social support by scales, all previously validated.

RESULTS

The association between sex and the physical activity level of adolescents was partially mediated by the social support of parents (β=0.79; p<0.001) and friends (β=2.96; p<0.001), and the association between age and physical activity level was partially mediated by parents' social support (β=0.78; p<0.001). The associations between sex and age and physical activity levels of adolescents were mediated by the social support of parents and friends.

CONCLUSIONS

Differences in physical activity levels between adolescent females and males and between younger and older adolescents may be partially explained by differences in social support provided by parents and friends. Implementation strategies to increase the social support of parents and friends may help reduce the differences in physical activity levels between these subgroups of adolescents.

A peer-led physical activity intervention in schools for adolescent girls: a feasibility RCT

Background

Girls are less active than boys and few adolescent girls meet physical activity (PA) guidelines. Peers are an important influence on the views and behaviours of adolescent girls, yet many PA interventions involving peers use formal approaches that may not harness the power of peer groups. More informal peer-led PA interventions, which work within proximal peer groups, may hold promise for increasing girls’ PA.

Objectives

To examine the feasibility, evidence of promise and cost of the Peer-Led physical Activity iNtervention for Adolescent girls (PLAN-A), a peer-led PA intervention.

Design

Phase 1 comprised formative work and a pilot study conducted in one secondary school. Phase 2 was a feasibility study comprising a pilot randomised controlled trial in six secondary schools, including process and economic evaluations.

Setting

Six secondary schools in South Gloucestershire and Wiltshire, recruited from schools above the median local Pupil Premium (i.e. more deprived).

Participants

Year 8 girls (aged 12–13 years).

Intervention

Year 8 girls nominated other girls in their year who are likely to be influential (e.g. who they look up to, are good listeners); the 18% most nominated were invited to be peer supporters (PSs). PSs attended 2 consecutive days of training (plus a top-up day 5 weeks later) outside the school site, led by pairs of PS trainers, to increase their knowledge about PA and their capabilities and confidence to promote PA in their friendship group.

Main outcome measures

Measures focused on establishing evidence for feasibility and promise: recruitment and retention of Year 8 girls and PSs, data provision rates [accelerometer and questionnaire collected pre randomisation/beginning of Year 8 (T0), end of Year 8 (T1) and beginning of Year 9 (T2)], intervention acceptability, PS training attendance, intervention cost, and the between-arm difference in weekday minutes of moderate to vigorous PA (MVPA). A process evaluation was conducted.

Results

Six schools were recruited: four PLAN-A (n = 269) and two control (n = 158). In total, 94.7% of Year 8 girls participated. A total of 55 (17–24% of Year 8 girls) PSs were trained (attendance rate 91–100%). Five girls were trained as PS trainers. Questionnaire data provision exceeded 92% at all time points. Accelerometer return rates were > 85% and wear-time criteria were met by 83%, 71% and 62% of participants at T0, T1 and T2, respectively. Mean weekday MVPA did not differ between intervention arms at T1 (1.1 minutes, 95% CI –4.3 to 6.5 minutes) but did at T2 (6.1 minutes, 95% CI 1.4 to 10.8 minutes), favouring PLAN-A. The mean cost of intervention delivery was £2685 per school or £37 per Year 8 girl. Process evaluation identified good fidelity, engagement and enjoyment of the PS training and peer-support strategies. PSs needed more guidance on how to start conversations.

Limitations

Accelerometer data provision was lowest at T2, suggesting a need for strategies to increase compliance.

Conclusions

Informal peer-led intervention approaches, such as PLAN-A, hold promise as a means of promoting PA to adolescent girls.

Future work

A definitive randomised controlled trial of PLAN-A is warranted.

Trial registration

Current Controlled Trials ISRCTN12543546.

Funding

This project was funded by the National Institute for Health Research (NIHR) Public Health Research programme and will be published in full in Public Health Research; Vol. 7, No. 16. See the NIHR Journals Library website for further project information. The work was undertaken with the support of the Centre for the Development and Evaluation of Complex Interventions for Public Health Improvement (DECIPHer), a UK Clinical Research Collaboration (UKCRC) Public Health Research Centre of Excellence. Joint funding (MR/KO232331/1) from the British Heart Foundation, Cancer Research UK, Economic and Social Research Council, Medical Research Council, the Welsh Government and the Wellcome Trust, under the auspices of the UKCRC, is gratefully acknowledged. This study was designed and delivered in collaboration with the Bristol Randomised Trials Collaboration (BRTC), a UK CRC-registered clinical trials unit in receipt of NIHR clinical trials unit support funding. The intervention costs were jointly funded by South Gloucestershire Council and Wiltshire Council.

Predictors of dropout in the school-based multi-component intervention, 'Mexa-se'

To identify the predictors of dropout in the 'Mexa-se' intervention according to the body mass index (BMI) category. This was a controlled, non-randomized study. The intervention included: (i) increase in the intensity of physical activities (PA) in physical education (PE) classes; (ii) active recess; (iii) educational sessions on PA, nutrition and body image; and (iv) educational materials. Dropout was considered when students dropped out of intervention, or did not reach 75% attendance in PE classes. The independent variables were gender, age, study period, socioeconomic status, BMI, PA, screen time, food consumption, health perception, attitudes toward PA, self-efficacy for PA, perception of the school environment, body image and self-esteem. Binary logistic regression analysis was used. The dropout rate was 26.8%. In the total sample and among students with an adequate BMI, there was a greater probability of dropout with an increase in age. For overweight students, increased age and socioeconomic status, and studying in the afternoon period were predictors of dropout from the intervention. Socio-demographic factors were predictors of dropout from the 'Mexa-se' intervention; the associated factors differed based on the BMI category.

Perceived neighborhood environment and physical activity among high school students from Curitiba, Brazil

OBJECTIVE

To analyze the association between perceived neighborhood environment and physical activity (PA) in high school students from Curitiba (PR), Brazil.

METHODS

A sample of 1,611 high school students from public schools was surveyed. The PA was assessed through questions, engaged for at least 20 minutes or 60 minutes. Perceptions on neighborhood environment were assessed through ten questions about neighborhood characteristics. Gender, age and number of cars in the household were self-reported and used as confounding variables. Absolute and relative frequencies were used in the sample, and associations were tested through adjusted logistic regressions for the confounding variables and stratified by gender (p < 0.05).

RESULTS

The adjusted analyses showed that the variables "interesting things" among girls (OR = 1.77; 95%CI 1.05 - 2.96) and "there are places I like" (OR = 2.18; 95%CI 1.33 - 3.58) and "I see people my age", among boys, were associated with PA of at least 20 minutes/day once a week. Additionally, among boys, "I see people my age" was associated with 60-minute (OR = 1.68; 95%CI 1.15 - 2.45). Perceiving the neighborhood environment as "very good" was associated with higher chances of taking up PA among girls (OR = 1.92; 95%CI 1.15 - 3.22) and boys (OR = 3.13; 95%CI 1.97 - 4.97).

CONCLUSION

A positive perception of the environment was associated to PA practice among boys and girls in this sample. The results suggest that some environmental characteristics which make neighborhoods more attractive could be related to PA among adolescents.

Rationale and methods of a cluster-randomized controlled trial to promote active and healthy lifestyles among Brazilian students: the "Fortaleça sua Saúde" program

Background

Interventions on adolescents’ lifestyle are important, but the main mechanisms that explain the changes (mediating variables) on lifestyle are unclear. This paper presents the rationale and methods of an intervention program focused on promoting active and healthy lifestyles (especially physical activity [PA] practice and reducing screen time) among Brazilian students-the Fortaleça sua Saúde program (Portuguese for “strengthen your health”).

Methods/Design

This is a school-based cluster-randomized controlled trial. Three intervention and three control (no intervention) full-time public schools were randomly selected in Fortaleza, northeastern Brazil. Students (n = 1,272) from classes in Grades 7–9 were eligible, and 1,085 (548 in the intervention and 537 in control schools) completed the baseline and follow-up measures. The program duration was approximately four months and took place in 2014. Intervention strategies focused on teacher training, activities on health in the curriculum, active opportunities in the school environment (the availability of equipment for PA), and health education (health materials for students and parents). Data collection was undertaken before and immediately after the intervention. The primary variables included the practice of PA (weekly PA volume, PA behavior change stage and preference for PA during leisure-time) and screen time (TV and computer/video games). Potential intrapersonal, interpersonal and environmental mediators of PA and screen time were evaluated by a standardized questionnaire. Other lifestyle components (e.g., eating habits, substance use), psychological (e.g., self-rated health, body satisfaction) and biological (general and abdominal obesity) aspects, as well as academic performance were also evaluated in the total sample. Depressive symptoms, eating disorders, sleep quality, objectively-measured PA, and sedentary time were evaluated in obese students.

Discussion

If effective, this program will contribute to the development of public policies for the promotion of active and healthy lifestyles in youth, especially those from low- and middle-income countries. The main intrapersonal, interpersonal and/or environmental mediators of PA and screen time may also be indicated. Finally, we anticipate that the proposed strategies may be adaptable to public schools and may even be extended to the entire school system.

Trial registration

ClinicalTrials.Gov: NCT02439827. Registration date: May 3, 2015.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-015-2543-2) contains supplementary material, which is available to authorized users.

Physical activity and social support in adolescents: analysis of different types and sources of social support

Little is known about the influence of different types and sources of social support on physical activity in adolescents. The aim of this study was to analyse the association between physical activity and different types and sources of social support in adolescents. The sample consisted of 2,859 adolescents between 14-19 years of age in the city of João Pessoa, in Northeastern Brazil. Physical activity was measured with a questionnaire and social support from parents and friends using a 10-item scale five for each group (type of support: encouragement, joint participation, watching, inviting, positive comments and transportation). Multivariable analysis showed that the types of support provided by parents associated with physical activity in adolescents were encouragement for females (P < 0.001) and adolescents between 14-16 years of age (P = 0.003), and transportation (P = 0.014) and comments (P = 0.037) for males. The types of social support provided by friends were: joint participation in male adolescents (P < 0.001) and in these 17-19-year-olds (P < 0.001), and comments in both genders (males: P = 0.009; females: P < 0.001) and 14-16-year-olds (P < 0.001). We conclude that the type of social support associated with physical activity varies according to its source, as well as the gender and age of the adolescents.

Physical activity, psychosocial and perceived environmental factors in adolescents from Northeast Brazil

The aim of this study was to evaluate the association between levels of physical activity, psychosocial and perceived environmental factors in adolescents from Northeastern Brazil. A cross-sectional epidemiologic study was conducted with 2,859 adolescents enrolled in secondary schools (57.8% females; mean = 16.5 years; SD = 1.2) in the city of João Pessoa, Paraíba State, Brazil. The following physical activity correlates were measured: attitude, self-efficacy, social support from friends and parents, and perceived environmental characteristics. Physical activity was measured using a questionnaire. Multivariable ordinal logistic regression with proportional odds model analysis showed that the following factors are positively related to physical activity levels in adolescents: attitude, self-efficacy, as well as social support from parents and friends. Physical activity intervention programs should increase self-efficacy and social support from parents and friends, as well as a positive attitude toward physical activity.

Reliability and validity of a physical activity social support assessment scale in adolescents--ASAFA Scale

OBJECTIVE

To analyze the reliability and validity of a scale used to measure social support for physical activity in adolescents - ASAFA Scale.

METHODS

This study included 2,755 adolescents (57.6% girls, 16.5 ± 1.2 years of age), from Joao Pessoa, Paraiba, Brazil. Initially, the scale was consisted of 12 items (6 for social support from parents and 6 from friends). The reliability of the scale was estimated by Cronbach's alpha coefficient (α), by the Composite Reliability (CR), and by the model with two factors and factorial invariance by Confirmatory Factor Analysis (CFA) adequacy.

RESULTS

The CFA results confirmed that the social support scale contained two factors (factor 1: social support from parents; factor 2: social support from friends) with five items each (one item was excluded from each scale), all with high factor loadings (> 0.65) and acceptable adjustment indexes (RMR = 0.050; RMSEA = 0.063; 90%CI: 0.060 - 0.067); AGFI = 0.903; GFI = 0.940; CFI = 0.934, NNFI = 0.932). The internal consistency was satisfactory (parents: α ≥ 0.77 and CR ≥ 0.83; friends: α ≥ 0.87 and CR ≥ 0.91). The scale's factorial invariance was confirmed (p > 0.05; Δχ2 and ΔCFI ≤ 0.01) across all subgroups analyzed (gender, age, economic class). The construct validity was evidenced by the significant association (p < 0.05) between the adolescents physical activity level and the social support score of parents (rho = 0.29) and friends (rho = 0.39).

CONCLUSIONS

The scale showed reliability, factorial invariance and satisfactory validity, so it can be used in studies with adolescents.

Perceived environmental characteristics and psychosocial factors associated with physical activity levels in adolescents from Northeast Brazil: structural equation modelling analysis

This study aimed to investigate the direct and indirect associations between perceived environmental characteristics and psychosocial factors and physical activity levels in adolescents from Northeast Brazil. The sample was composed of 2,361 adolescents aged 14-19 years (56.6% female). Physical activity was measured using a questionnaire and environmental (perceived environmental characteristics) and psychosocial (self-efficacy, social support from parents and friends for physical activity) factors with previously validated scales. Perceived environmental characteristics were not directly associated with the levels of physical activity, but exhibited significant indirect associations, mediated by self-efficacy in males. Self-efficacy and social support were positively and directly associated with physical activity levels, and part of the associations between social support and physical activity was mediated by self-efficacy. Perception of self-efficacy and social support, important factors associated with physical activity levels in adolescents, should be the target of interventions aimed at increasing physical activity. Favorable environments for physical activity also need to be considered, since they have a positive influence on the self-efficacy of adolescents.

Physical activity in adolescents: analysis of the social influence of parents and friends

OBJECTIVE

To analyze the association between physical activity and social support from parents and friends on the physical activity level among adolescents.

METHODS

Data from 2,361 adolescents (56.6% females; mean age 16.4; SD = 1.2), from public and private high schools were analyzed. The physical activity level of the adolescents, parents, and friends were measured through a questionnaire. Parents' and friends' support and self-efficacy were measured using two previously tested scales. Data analysis was performed using the structural equation modeling in IBM® SPSS® Amos™ 20.0.

RESULTS

Physical activity of friends was directly associated with physical activity level of adolescents. Physical activity of the father was associated with that of their sons, and the physical activity of mother was associated with that of their daughters. An indirect association was identified between the physical activity of parents and friends with physical activity level of the adolescents, mediated by social support. Social support was directly associated with physical activity in adolescents of both genders and indirectly mediated by self-efficacy.

CONCLUSIONS

Parents and friends have a social influence on adolescents' level of physical activity through the mechanism of behavior modeling or through social support, mediated by self-efficacy.