Physical activity engagement has proven important in the primary and secondary prevention of several chronic conditions (Warburton et al., 2006). However, the process of ingraining long-term lifestyle physical activity patterns has proven to be a difficult enterprise (Muller-Riemenschneider et al., 2008). An individual's lifestyle is the sum of cumulative day to day choices. These choices are made in response to stimuli on a background palate of intrinsic and extrinsic factors that have led to ingrained habitual patterns (Telama et al., 2005). Evidence has shown that lifestyle patterns developed during childhood and adolescence have a tendency to carry over into adulthood (Hallal et al., 2006; Telama et al., 2013).
In addition to the long-term benefits of regular physical activity, increases in physical activity among youth have proven to be associated with a number of important factors; including nutritional intake (Storey et al., 2009), academic performance (Rasberry et al., 2011; Trudeau and Shephard, 2010), depressive symptoms (Aman et al., 2009; Rothon et al., 2010; Motl et al., 2004), stress (Twisk, 2001), risk-taking behaviours (Geckil and Dundar, 2011), self-esteem (Ekeland et al., 2005a; 2005b; Twisk, 2001) and wellness (Rachele et al., 2014). In order to better understand the context of youth physical activity engagement, it is important to establish its associated predictors. The knowledge of such predictors may influence the planning and structure of physical activity and health promotion interventions aimed at youth.
Autonomy is one of three basic 'psychological needs' that individuals need to satisfy, along with competence and relatedness, that comprise self-determination theory. Autonomy has been defined as the ability to do what one does independently, without being forced to do so by some outside power, and is in essence self-determination (Boden, 2008). It is fostered by a context that provides autonomy support in the form of acknowledging the behavior's perspective, opportunity for initiative, and the provision of choice (Deci et al., 1994; Ryan, 1982). A recent systematic review on exercise, physical activity, and self-determination theory showed consistent support for a positive relationship between more autonomous forms of motivation and exercise, with a trend towards identified regulation predicting initial/short-term adoption more strongly than intrinsic motivation, and being more predictive of long-term exercise adherence (Teixeira et al., 2012). Among children aged 8-12 years, the provision of autonomy supportive environments has proven to increase rates of play and physical activity (Roemmich et al., 2012); .
While there appears to be a positive relationship between autonomy and physical activity, comparable relationships are yet to be established among adolescent populations. Understanding this relationship may aid in the design of interventions facilitating physical activity engagement among young people. Specifically, the opportunities given to participants to independently make decisions about their physical activity. The purpose of this investigation was to examine the association between adolescents' self-reported physical activity (whether or not they met minimum recommended physical activity guidelines (Department of Health and Ageing, 2004)) and their autonomy. It was anticipated, based on existing literature (Hagger et al., 2003; 2005; Lim and Wang, 2009), that a positive association would be found between meeting minimum physical activity guidelines and autonomy.
This investigation included a total of 384 adolescents (95 males and 177 females) aged between 12 and 15 years. Participants were recruited from six secondary schools in metropolitan Brisbane, Australia. Schools were categorized as either from low, medium, or high socioeconomic status (SES) backgrounds. School SES background was determined by the Australian Curriculum, Assessment and Reporting Authority's Index of Community Socio-Education Advantage (ICSEA). Details on the ICSEA scale used in this study have been published elsewhere (Rachele et al., 2013, Australian Curriculum Assessment and Reporting Authority, 2012). Participants were recruited from two non-denominational same-sex private schools classified as high SES; one same-sex and one coed private school classified as mid SES, both with religious affiliations, and one non-denominational public school; and one non-denominational public school classified as low SES.
International Physical Activity Questionnaire for Adolescents: The International Physical Activity Questionnaire for Adolescents (IPAQ-A), adapted from the International Physical Activity Questionnaire Long Version, was developed for use in adolescents (Hagstromer et al., 2008; Rachele et al., 2012). This adapted version also measures physical activity over the previous seven days, and covers four domains of physical activity being school-related physical activity, including activity during physical education classes and breaks, transportation, housework, and leisure time. In each of the four domains, the numbers of days per week and time periods per day spent walking, in moderate activity and in vigorous activity are recorded. Variations from the adult version include questions about physical activity at work being replaced by physical activity at school, and including only one question about physical activity in the garden or at home (versus 3 in the standard IPAQ) (Hagstromer et al., 2008). Since its establishment, the IPAQ-A has been used in used in several empirical studies (De Bourdeaudhuij et al., 2010; Hagstromer et al., 2008; Rachele et al., 2014), and significant associations have been found for moderate-to-vigorous physical activity among adolescents aged 12 to 15 years when compared to accelerometers (r = 0.20, p
Total time spent per week engaging in moderate-to-vigorous physical activity can be summed across each of the four domains, and computed to establish if participants are meeting physical activity recommendations (World Health Organization, 2010, Department of Health and Ageing, 2004). The IPAQ-A was used in this way for this investigation to identify those participants who were (and were not) meeting the minimum physical activity levels recommended for obtaining health benefits.
Self-Determination Scale: Autonomy was assessed using Sheldon and Deci's (Sheldon and Deci, 1996) 10item Self-Determination Scale. This 10-item scale has two factors; awareness of self and perceived choice. For each item, participants were asked to indicate which of two statements is more true for them (e.g., "A. I sometimes feel that it's not really me choosing the things I do" and "B. I always feel like I choose the things I...