Association between intention for physical activity practice, social support and physical activity

– Intrapersonal and interpersonal aspects have been widely correlated to variations on the physical activity (PA) levels. The aim of this study was to examine the moderating effect of intention for PA practice on the association between social support and leisure PA levels in a sample of college students from Curitiba, Brazil. A questionnaire was administered in a sample of 349 college students from a Physical Education undergraduate program. The variables intention to PA practice, social support (family and friends) and leisure-time PA were obtained through interviews. Poisson regression was used to test the moderating effect of intention to PA practice on the association between social support and leisure-time PA levels. The intention for PA practice showed no moderating effects on leisure PA. Social support from friends was associated with achieving recommended PA levels (≥150min/week), regardless of intention for PA practice (PR: 1.45; 95% CI: 1.09-1.93). In this study, moderating effect of intention for PA practice on the association between social support and leisure-time PA has not been found.


INTRODUCTION
Physical activity (PA) is a complex behavior influenced by personal, social, environmental and community aspects 1,2 . Recently, there has been a growing interest in identifying variables that may explain adherence and maintenance of physical activity in order to promote more effective interventions that contemplate multiple levels of influence 1 . Thus, intrapersonal and interpersonal aspects have been widely analyzed and are those that best have explained variations in PA levels 1 .
The intention for physical activity practice (IPAP) shows how much individuals are willing to change their behavior and it is possible to identify both their readiness and transition to active behavior 3 . At the interpersonal level, social support (SS) is described as the action that helps the person to adopt and / or maintain a particular PA practice and may occur in different ways, such as: instrumental or direct, psychological or emotional, and instructional or informational support [4][5][6][7] .
In Brazil, the evidence on the relationship between IPAP 8 , SS 9 and PA has increased in recent years and its results have shown a positive association in adolescents, adults and the elderly [10][11][12] . In general, investigations have focused on specific groups and direct relations between SS, IPAP and PA 8,9 . However, the moderating role of intrapersonal and interpersonal aspects has been little explored.
The literature has shown investigations on the relationship between IPAP and SS in isolated Brazilian population groups [10][11][12] . This study intends to investigate these correlations together in order to find how much the combination between them explains the probability of practicing leisure PA at recommended levels. It is possible that SS indirectly acts on PA by increasing IPAP and this, in turn, directly acts on PA levels. This relationship may be important for the sample of this study, physical education undergraduate students, who may have chosen the course because they have an interest in the practice of PA, but according to literature, it has demonstrated low PA levels throughout the course 15 .
Thus, understanding the aspects that can explain the practice of PA at recommended levels can improve health promotion initiatives for university students, such as PA promotion programs at universities 1,16 . The aim of this study was to verify the moderating effect of IPAP on the association between SS and the moderate and vigorous leisure activity physical levels (MVPA) in university students from Curitiba, Paraná, Brazil.

Designing
This study is part of a project that monitors the lifestyle of university students in the city of Curitiba-PR conducted in 2013. The study was ap-

Sample
Participants were non-probabilistically selected for convenience. Students of the Physical Education undergraduate program (Bachelor's degree and Licentiate) were invited to compose the sample (n = 465). The sample power was calculated a posteriori using the GPower 3.1.1 software, allowed detecting associations of prevalence ratio of 1.44 with a power of 80% to alpha value of 5%.

Instruments
• PA practice PA practice was measured using the IPAQ -short version (International Physical Activity Questionnaire), where students reported "how many days a week" and "how much time per day" they practiced MVPA during a usual week during leisure time 17 . The weekly PA practice time was categorized according to current recommendations used in other studies 12 , with participants being classified as "≥150min / week" or "<150min / week".
• SS SS was considered as an independent variable and was evaluated through six questions related to the frequency with which in the last three months a friend or relative performed incentive actions (practiced, invited, encouraged) the PA practice 18 . Each question presented three response options (never, sometimes, always), which were summed to produce a score (0-6 points), for each SS source. Then, according to the authors' criteria, the score was categorized according to the median and the variable was classified into two SS levels (High versus Low) from both family and friends.
• IPAP IPAP was assessed by four questions. The participant was first questioned about his intention to practice PA on a regular basis in the next two weeks. The choices were "yes" or "no." The two subsequent questions asked about the chance of the individual to practice PA on a regular basis in the next two weeks and three months, respectively. For both there were four answer options: none, low, intermediate or high. In the last question, the participant should indicate the option that best represented his behavior in the PA practice 19 . Later, the scores and the variable categorized according to the median into "High Intention" and "Low Intention", were calculated.

• Covariables
Variables age, body mass index (BMI), socioeconomic status (SES), gender and marital status (without partner/with partner) were included as covariables. Age group was evaluated by means of an age-related question and was later classified into categories: <18, from 18-24 and ≥ 25 full years. BMI was calculated based on height and body mass measurements using a digital scale and stadiometer (Wiso model W721). In order to classify BMI, the parameters of the World Health Organization (WHO) 20 were used, namely: BMI of 18.5-24.9 kg/m2, classified as normal; BMI of 25-29.9 kg/ m2 as overweight; BMI≥30 kg/m2 as obesity. Students aged <18 years were classified according to Cole et al 21 . SES was classified according to criteria established by the ABEP (Brazilian Association of Research Companies) 22 . For purposes of analysis, university students were grouped into three levels: High (A1 and A2), Intermediate (B1, B2, C1 and C2) And Low (D, E).

Data collection
Self-administered questionnaires with the guidance of two interviewers with average application time of 45 minutes per class were used. Days and times of collection were established by the university, respecting the class schedules. To identify possible doubts about the questionnaires and their application, a pilot study was carried out, with university students that were not included in the sample.

Data analysis
Data were analyzed with descriptive statistics by frequency distribution (absolute and relative) and chi-square test. Poisson regression for the estimation of Prevalence Ratios (PR), with confidence intervals (95% CI) was used to test the association between individual, interpersonal and PA variables. IPAP was tested regarding a possible moderating effect on the relationship between SS (family and friends) and PA. In the multivariate model (forced entry), only variable sex was selected because it was the only one presenting p value <0.20. Analyses were performed using the SPSS 20 and STATA 12.0 software and significance level was maintained at 5%.
In the adjusted analysis (Figure 1), high SS from friends for those with low IPAP presented a marginal and positive association with PA recommendations (PR: 1.59, 95% CI: 0.96-2.65 p = 0.071). The association between SS from friends and compliance with ≥150min / week of PA, regardless of IPAP, was maintained in the adjusted model (PR: 1.45; 95% CI: 1.09-1.93 p = 0.010).

DISCUSSION
High SS from friends for those with low IPAP presented marginal and positive association with practice of ≥150min / week of PA (PR: 1.59; 95% CI: 0.96-2.65 p = 0.071), that is, although IPAP is low, there is a tendency for SS from friends to increase the likelihood of practicing PA at recommended levels. A meta-analysis on SS has identified that individuals who receive higher SS present a more positive health status and health promotion behavior, that is, a greater chance of engaging in regular practice of PA 23 . Given the harm of physical inactivity, the present study presents intervention proposals to promote the practice of PA. Interventions aimed at encouraging habitual practice of PA have been considered a public health priority 24 . Thus, interventions that include activities based on SS from family and friends and operational strategies presented by the transtheoretical model of behavior change -TTM, which investigates the individual's intention to start a PA program can increase the acquisition of an active behavior 25 . It was identified that 45.3% of university students do not meet the minimum recommendation of PA, a result similar to a study carried out with Physical Education undergraduate students of Sergipe 26 , but lower than that found among students from three major areas (Humanities, Exact and Health Sciences) of Curitiba-PR (54.5%), reinforcing that low PA levels are prevalent in university students 15 . The results suggest that students in this area are more active when compared to those of other areas, which can be explained both by amount of PA performed in the course classes, since the national curricular guideline for the Physical Education course defines that the acquisition of skills must occur from theory-practice interaction 27 , as well as by the greater involvement and knowledge about PA.
The study confirmed the literature findings that individuals who frequently perform PA together or are invited by friends to participate in physical activities are more likely to comply with minimum PA recommendation. In the sample investigated, there was a positive association between high PA levels and high friends SS (p <0.001) and high IPAP in leisure (p <0.001). The finding is corroborated by another study conducted in the city of Curitiba, in which SS from family (OR = 2.77, 95% CI = 2.08-3.69) and friends (OR = 2.89, 95% CI = 2.18-3.85) increased by almost three times the likelihood of an individual achieving ≥150min / week of PA. This study also found that high IPAP increases by 2.5 times the likelihood of an individual to have active behavior (OR = 2.51, 95% CI = 1.80-3.51) 12 .
Regarding the characteristics related to IPAP, men (p <0.001) and university students with high SS from friends (p <0.001) presented high intention. No evidence was found of the association of SS from family with IPAP, but the fact that individuals are enrolled in a university and involved in a wide and complex network of social, cultural and environmental factors end up by affecting their behavior. Souza et al 8 verified the IPAP of university students in the health area through stages of behavior change, and found a significant difference in the proportion of students in the Physical Education course in the maintenance stage (performed physical activity for more than 6 months) compared to other areas (physical education 82.1%, nursing 33.3%, pharmacy 48.1% physiotherapy 31.3% and nutrition 28.6%), which demonstrates that knowing the benefits of PA can arouse interest in engaging its practice. When the preparation and action stages of physical education students were verified, 10.4% and 7.5%, respectively, they showed an intention to change their behavior in the near future or to maintain the physical activity that they began to change their behavior in the coming months 8 .
Females presented a marginal and inverse association with compliance with ≥150min / week of PA (PR: 0.74; 95% CI: 0.54-1.00 p = 0.054). In their study with college students, Gasparotto et al 15 found that males were more likely to meet PA recommendations. In general, women have lower leisure PA levels when compared to men, a characteristic observed in adolescence 10 and in adulthood 12 , which is related to social and cultural aspects, including the lack of incentive of family members for the practice of PA. Therefore, the participation of the family has great importance for the involvement of the adolescent in the practice of PA 29 . Educational actions with parents and family on the importance of the practice of PA and its benefits throughout life are suggested. Practical actions could also be carried out based on the interest and mobilization of parents in relation to the practice through the invitation and/or encouragement and/or practicing together, since there is a greater chance of this behavior being maintained in adult life 29 . As for the university's role in promoting PA, it is expected to serve as a driving force behind these initiatives beyond the experiences that physical education classes provide. It is suggested that PA should be developed on the back shift, improve physical abilities, encourage corporal practice and participation in university competitions.
A study carried out in the city of Pelotas, RS, showed that higher SS from family or friends increases by two times the probability of performing PA. However, as the individual grows, participation in PA with the family decreases, while participation with friends increases 29 . Results from the present study point in this direction, since no association of SS from family with the meeting of PA recommendations was found, while high SS from friends increased by 45% (PR: 1.45; CI 95% : 1.09-1.93 p=0.010) the chance of achieving recommended PA levels. Educational actions should be encouraged in all levels of university coexistence (university, friends, community). Active mobility campaigns can positively contribute to university students' PA levels 30 .
The study presents characteristics that should be considered when interpreting the results. The cross-sectional design prevents larger cause and effect conclusions among variables. The study sample consisted of a group of university students particularly involved in PA practices, which may have attenuated the effect of SS and IPAP, as participants are exposed to a more favorable social environment and possibly more motivated to intrinsic practice. In addition, participants come from a single institution. These characteristics affect the extrapolation of results to university students from other areas of knowledge and locations. The use of self-reported PA measures can affect the classification of PA levels, but allowed the establishment of specific domains and contexts of PA, SS and IPAP.

CONCLUSIONS
SS from friends and IPAP are associated with compliance ≥150min/week of PA, when analyzed in isolation. SS from friends increases the likelihood of university students to fulfill ≥150min/week of PA. There is a tendency that high SS from friends contributes to increase IPAP. Interventions to increase university students' PA practice should provide involvement of friends. Future studies should explore multiple levels of influence that explain PA adherence and maintenance in a more specific way.