Adolescent physical activity: the role of parental social support and the level of physical activity. Social Support and Physical Activity of Parents and Adolescents.

Background: Maximising the level of physical activity in adolescents has been a concern for many researchers given the benefits provided by physical activity. Aim: To verify the relationship between the level of moderate vigorous physical activity (MVPA) of parents or legal guardians and that of social support (SS) with the level of MVPA in adolescents. Methods: Cross-sectional study that selected 1390 (59.6% female) adolescents. The questionnaires IPAQ, QAFA and ASAFA were used. Results: In relation to boys, receiving incentives from parents who “assist always” (OR=1.96 – CI95%=1.16–3.32) and having parents/legal guardians who meet the MVPA recommendations (OR=2.78 – CI95%=1.76–4.38) was associated with meeting the MVPA recommendations. The probability increases when adjusted by socioeconomic status (OR=3.47 – CI95%=1.73–6.96) or education level (OR=4.20 – CI95%=1.96–9.02). Regarding girls, parents who “encourage sometimes” was associated negatively (OR=0.61 – CI95%=0.37–0.98) and meet the MVPA recommendations (OR=2.04 – CI95%=1.46–2.87) was associated positively with meeting the recommendations for adolescents. The likelihood raises when adjusted by socioeconomic status (OR=2.11 – CI95%=1.36– 3.29) or education level (OR=4.30 – CI95%=2.41–7.69). Conclusions: Having parents who meet with the physical activity recommendations demonstrated higher results in adolescents engaging 60 minutes of MVPA daily when compared to receiving social support, for both boys and girls.

case of adults, it is indicated to practise 150 minutes a week of moderate physical activity (MPA) or 75 minutes of vigorous physical activity (VPA) 6 .
In this sense, numerous national and international studies indicate that the level of social support (SS) in the family context, as well as in the peer group, is linked to higher levels of PA in adolescents [17][18][19] .
In addition, the fact that parents practise PA at the same time is a good model for children to get involved in PA [20][21][22][23] . A longitudinal study that included 13.000 students observed that PA engaged by parents showed an association with that engaged by their children 23 .
However, to date, the studies have presented the association of the PA level of parents or legal guardians and SS in isolation [20][21][22][23] . The present study seeks to investigate the chance that an adolescent has to comply with the MVPA recommendations if parents or legal guardians also comply with it and, in parallel, it investigates the SS received from parents or legal guardians to practise PA (encourage, practise together, transport, assist and comment on how well the adolescent is doing his/her PA). Once investigated, this gap can contribute to a better understanding of how to maximise the levels of MVPA in adolescents, with the support and example coming from parents (father, mother, caregiver).
Thus, the aim of this study was to verify the relationship between the level of MVPA of parents or legal guardians and that of SS with the level of MVPA in adolescents.

Methods
The study followed the standards of research involving human beings of the National Health Council (resolution number 466/2012), having been approved by the Research Ethics Committee of the Federal University of Paraná (CAAE: 98133218.8.0000.0102) and authorised by adolescents' the parents or legal guardians by means of a free and informed consent form. This is a cross-sectional study conducted in 2018 with a representative sample of adolescents aged 15 to 17 enrolled in a public high school.
For the preliminary sample calculation, an association of OR=1.49 was considered between SS and PA 24 , a prevalence of being insufficiently active of 50% 25 , a confidence level of 95% (α=0.05) with a power of 80% (β=0. 20), resulting in a minimum sample of 804 subjects. However, an increase of 30% was considered for possible losses and refusals, which estimated a minimum sample required for the study of 965 subjects. The sample was selected from the process of sampling by multiple stages, conglomerates, in three stages: 1st stage -all state schools were stratified according to each of the nine administrative regions of the city of Curitiba; 2nd stage -two schools were drawn in each regional; 3rd stage -a simple random selection of a class of each year was performed, according to the number of students, separated by sex, required for a given region. Finally, all students in each class were invited to participate in the study.
A total of 2506 adolescents were evaluated. Those who presented physical and/or cognitive limitations (informed by the school) (n=12) and were 18 years old (n=125) were exempt. We also excluded the adolescents who did not present the informed consent form (n=104), those who refused to participate in the study, or missed the day of collection (n=56), as well as those who answered the questionnaires incorrectly or did not answer about PA level (n=819). Thus, the analytical sample of the study was 1390 adolescents.
Statistical analyses carried out subsequently showed that this sample could identify statistically significant ratios above 1.36 and below 0.73, considering a power of 80% (β=20%), a confidence level of 95% (α=5%) and considering a prevalence of 34% of adolescents with low SS and who did not meet the minimum recommendations for PA.

Physical Activity -Parents / Legal Guardians and Adolescents
The moderate vigorous physical activity (MVPA) level of parents or legal guardians was measured through the IPAQ questionnaire -short version (International Physical Activity Questionnaire), in which parents or legal guardians reported "how many days a week" and "how long a day" they practised displacement) per week was categorised according to the current recommendations of MVPA practice ("it meets the recommendations" ≥150 minutes per week of MVPA practice and "it does not meet" (<150 minutes per week of MVPA practice) 6 .
The PA level of adolescents was evaluated by the Physical Activity Questionnaire for Adolescents (QAFA) 27 . This questionnaire was first developed in the checklist format by Sallis et al, 1996 28 27 . To analyse the MVPA level, it was classified as "it meets the recommendations" (≥60 minutes per day of MVPA practice) and "it does not meet" (<60 minutes per day of MVPA practice), to consider the recommendation by the WHO is that adolescents (13 to 18 years old) perform at least 60 minutes/day of MVPA to obtain health benefits 6 .
Social Support received from parents or legal guardians for the practice of Physical Activity.
The social support (SS) of the adolescents' parents or legal guardians to practise PA (physical activity) was measured by the scale of 5 items Social Support for Physical Activity Practice for Adolescents (ASAFA), which has satisfactory consistency (SS of parents α ≥ 0.77 and IFC ≥ 0.83) 29 . Adolescents reported the frequency (never=1, rarely=2, frequently=3, always=4) with which parents offered some type of SS for the practice of PA (encourage, practise, transport, assist, comment) during a typical or normal week 29 , through the questions: "How often do your parents encourage you to practise PA? Do they practise PA with you? Do they transport you or provide transportation so that you can go to the place where you practise PA? Do they assist you in PA? Do they comment that you are doing your PA well?" For purposes of analysis, and with the aim of ensuring comparability with similar studies 30 , the response options "rarely" and "frequently" were grouped and classified as "sometimes". Thus, the weekly frequency categories of SS were classified as never, sometimes and always.

Sociodemographic Information and Health
Sex was self-reported ("male", "female") and age was calculated from the date of birth (informed by the adolescent) subtracted from the date of data collection and divided by 365, resulting in: "15 years", "16 years", "17 years".
The nutritional status was calculated by the Body Mass Index (BMI), from the measured data of body mass and height (kg/height). The evaluation of the body mass was carried out by a trained researcher using a portable digital anthropometric scale (W721, Wiso, Brazil) with resolution of 100 grams and capacity of 150 kilograms (Kg). The adolescents were barefoot, wearing only light clothing and were guided to maintain their anatomical position, to position themselves with their backs to the scale and to distribute their body mass equally between both feet. A portable stadiometer (W721, Wiso, Brazil) was used to measure the total height of the participants. The participants were in the anatomical position with the head positioned in the Frankfurt Plan and, at the time of measurement, they performed an inspiratory apnea. Two measurements were performed and in case of divergences of more than 0.1 centimetres (cm) between measurements the procedure was performed again 31 . The technical error of measurement was obtained by carrying out a number of repeated measurements on the same subject, either by the same observer, taking the differences and entering them into an appropriate equation. For intra-observer TEM of the two measurements taken it was used the following equation: , where "D" is the difference between measurements and "N" is the number of individuals measured 32 . Likewise, intraclass correlation coefficient (ICC) was calculated to verify the reliability of the measurements, giving a result of 0.96.
The identification of nutritional status was carried out through the classifications of BMI Z scores for each sex and age proposed by the WHO, being: Low weight = <-2 SD (standard deviation), Eutrophic = ≥-2SD and <+1DP, Overweight = ≥+1 SD and <+2DP and Obesity = ≥+2 SD, classified as "not overweight" and "overweight" 33 . The education level of the main family breadwinner and his/her socioeconomic status (SES) were evaluated with a standardised questionnaire 34 . The Education level was classified as: Elementary School, Secondary School or higher Education levels. SES was classified into three categories: "low" (class C+D), "medium" (class B1+B2) and "high" (class A1+A2) (ABEP, 2016) 34 .

Collecting data
Parents and/or legal guardians received the questionnaire at home to answer it. The parents'/legal guardians' questionnaire was sent out by the adolescents together with the terms of consent for the adolescents to agree to. Adolescents who had parental permission to participate in the survey answered the questionnaire at school during physical education classes with the help of the researchers who applied the questionnaire.

Data Analysis
After having identified the data distribution by the Kolmogorov-Smirnov test, descriptive statistics were used to distribute absolute and relative frequencies. The chi-square test (χ 2 ) was used to verify differences in proportions in relation to sex and recommended levels of MVPA in adolescents.
Pearson's chi-square test was used to compare proportions between genders, then a post hoc test was used to demonstrate which categories showed the greatest difference.
Binary logistic regression was used to test the relationship among the study variables (between the level of MVPA of parents or legal guardians and that of SS with the level of MVPA in adolescents). By the enter criterion, the value of p ≤0.20 for the entry of the variable in the adjusted model was adopted. Afterwards, the interaction for age, nutritional status, main breadwinner's education level and socioeconomic status (SES) logistic regression analysis models were introduced (multiplication of the possible moderating variable with the independent variable -example: age * SS: practice). In all, 20 interactions were tested (age, nutritional status, main breadwinner's education level and SES with the SS scale and MVPA parentes -significant values were presented in tables 2 and 3) To avoid bias related to the complex sample selection process (cluster stratification), the association analyses were corrected by the complex design using the SPSS software version 23.0 "complex sample" command. This procedure was used to ensure that the estimates reflect the population data of the elementary units in the sample.

Results
The sample was composed by 1390 adolescents (59.6% female) and their respective parents/ legal guardians. Table 1 show the variables of the study stratified by sex, where: nutritional status (p=0.001), SES (p=0.015) and the level of MVPA of parents (p=0.021) showed significant differences (Table 1).

Discussion
Numerous studies indicate that the level of SS in the family context, as well as recommended levels of PA (physical activity) from parents or legal guardians are linked to higher levels of PA in adolescents [16][17][18][19][20][21][22][23]35 . However, scientific literature has analysed these variables independently. Aiming at this, the present study sought to investigate the variables in the same sample of adolescents, in order to analyse how much the fact of having parents or legal guardians physically active and receiving their support for the practice of PA could contribute to achieve the recommendations of Moderate Vigorous Physical Activity (MVPA) in adolescents.

Boys
In the present study, for boys, the support of parents related to assist and the fact of having parents who meet the MVPA recommendations were associated with meeting recommended MVPA levels. A systematic review 35  Parental SS for adolescents to engage PA is a crucial factor, however, the scientific literature has reported a greater emphasis on social support from friends than that provided from families, for older adolescents, according to a systematic review performed by Mendonça and colleagues (2014) 38 .
Nevertheless, having active parents (i.e., parents who comply with PA recommendations) as role models, seems to have a positive influence even with older adolescents, as indicate the results of our study. Thus, in this age phase, adolescents may not give as much relevance to the SS of parents, but they may give as much importance to the example they offer about PA practice 38 .
In a systematic review 39 of studies that examined both children's and parents' PA, conducted in countries with high development index (United States, United Kingdom, Australia, Canada, France and Portugal) all with cross-sectional design, it was showed that fathers' MVPA was associated with that MVPA of children, as well as the participation in vigorous activities of children was associated with the practice of VPA (vigorous physical activity) of parents 39 . For mothers, the practice of MPA (moderate physical activity) was associated with the practice of MPA that of children 39 . Both associations were confirmed for weekdays and weekends 39 .
The physical activities reported by parents in their childhood and adolescence were also associated with higher levels of PA among adolescents 40 . Adolescents with physically active parents in the past and currently, were six times (OR=6.670 -CI 95% =1.940-2.790) more likely to be physically active compared to adolescents whose parents/legal guardians were not physically active in the past 40 .
Therefore, it seems necessary to understand these parental constructions that measured PA since childhood 39,40 .

Girls
In the case of girls, the fact of receiving incentives from parents (encourage) and having parents/legal guardians who comply with the MVPA recommendations was associated with complying the MVPA recommendations, encourage was associated negatively and comply with the MVPA recommendations positively. Piola et al 36 , in the city of Curitiba (Brazil), in a study of adolescents found that the fact that parents "always" commented positively on the activities was absolutely associated with the practice of PA in post-pubertal adolescents (girls and boys) (OR=2.60 -CI 95% =1.01-6.71). Variations in associations between different types and sources of SS can also be observed according to the age and sex of adolescents 19,38,41 . As in the study of Prado et al 30 , where having parents who "practise" PA together with their daughters was positively associated with the practice of PA (five or more days in the week of 60 minutes of MVPA) for girls. Some studies show that SS from friends seems to be more associated with meeting the PA recommendation in older adolescents 38 . In this sense, encouraging girls to practise PA could be an important tool, coming from parents and family members, to maximise levels of PA. This is due to the fact that an increased SS contributes to raise the level of PA in adolescents 19 .
Complying with the MVPA recommendations established for parents contributes to increasing the chance of adolescent girls complying with the MVPA recommendation by almost twice as much.
Bound together, these findings demonstrate that the regular practice of parents' PA, combined with the support they provide to their children for, this purpose, are important factors not only for adolescents in PA, but also for the practice of MVPA. When close people are present and value their behaviour, adolescents' self-esteem tends to rise; thus, it increases their perception of self-efficacy 21 ; what can contribute, inexorably, to higher levels of PA 21 . Parental or legal guardian encouragement can have a direct influence on the active participation of adolescents, since it can lead adolescents to participate in a more automatic process, establishing routines.
The results confirm the importance of the family environment for adolescent's PA 19,22,35,38,39 . It indicates that the influence of the family environment (receiving support from parents or legal guardians and having active parents or legal guardians) in the dynamic behaviour of adolescents, operates, in a way, through the attitudes they receive from parents or legal guardians, such as support and especially the example of being physically active 23,41 . In the present study, having Notwithstanding, on the basis of the results of Global Matrix report, a significant low negative correlation was observed between the overall PA and some sociodemographic indicators (e. g. Human Development Index and the growth national income per capita) 42 . For this reason, developing effective strategies to offer PA opportunities for all should be a national public health prime concern in all countries despite the SES.

Limitations
Some points should be considered when interpreting the results of this study. One of them is reverse causality, a common characteristic in studies with a cross-sectional design, which does not allow investigating a cause and effect relationship or determining the direction of the relationships.
However, this design has been used in several studies like this. The study was developed in a single Brazilian city and has typical characteristics of well-developed urban centres, which does not allow extrapolating the findings to rural centres and other cities in the country.
The sample only consisted of adolescent students from public schools making it impossible to extrapolate the results to higher classes. However, the representative sample and statistical analyses ensure an interpretation of the data for large populations of public schools, an important point in the field of interventions related to public and preventive health.
The use of reported measures depends on the accuracy and recall power of the respondent's responses. In an attempt to minimise this bias, researchers were trained to assist adolescents in answering questionnaires. The instrument used to measure physical activity does not allow the identification of all domains and contexts in which the activities were practised. For this reason, obtaining a more accurate measure would contribute to reducing type 1 error. However, as it is a large study, with a representative sample, the use of questionnaires proved to be the best alternative.
In the present study, having parents who meet with the PA recommendations demonstrated higher results in adolescents engaging 60 minutes of MVPA daily when compared to receiving SS, for both boys and girls. In particular, regarding girls and aiming that one of the big problems related to physical inactivity is to make girls more physically active, the results of this study contribute to warn about the importance of having parents who meet with the recommendation of PA. The repeated encouragement and forms of support from parents/legal guardians, in addition to the example of being physically active, can initiate and build confidence so that the perceived behavioural control is  Tables   Table 1. Sociodemographic information and health, social support and data on physical activity stratified by sex (n=1390).