The current study tested the basic factor of increasing choice on youth physical activity. Given that past research has demonstrated the importance of motivation for children to engage in physical activity [32, 38], the current study relied on SDT as a framework to understand how choice can increase intrinsic motivation to engage in physical activity. According to SDT, setting the environment so that it provides opportunities to make choices allows the individual to experience autonomy, which enhances intrinsic motivation to engage in a behaviour at that time and in the future [4, 5]. Providing autonomy through an increased choice of active toys in a child's environment increased the duration and intensity of physical activity, especially of girls. When presented with no choice, girls were neither as active as long nor as intense as boys. This is not surprising as girls are typically less active than boys [39, 40], but by simply providing girls with a greater choice of active toys they can be motivated to engage in physical activity equal to boys.
There are few controlled laboratory studies of the effect of choice on children's physical activity participation. We manipulated access to the number of resistance training machines . This model allowed choice to be studied while controlling for exercise mode. Children performed greater repetitions and lifted more total weight when provided access to 7 resistance training machines than when provided access to only 1 machine.
More recently, we (unpublished results) provided children access to no choice (1 toy) or two different levels of choice (3 toys or 5 toys) of traditional physically active games such as indoor basketball, hockey, and jumping games. Consistent with the current results, boys engaged in 130% longer active play and 150% greater activity intensity than the girls in the no choice (1-toy) group. However, providing a choice of 3 or 5 active toys increased physical activity time (42% versus 190%) and intensity (8% versus 180%) more for girls than boys. The consistency of these results with those of the current study argues for a gender difference in children's responsiveness to choice. Qualitative research agrees with these quantitative results in that twice as many girls than boys identify having a choice of activities as a motivational factor for physical activity .
Yet, SDT would suggest that the need for autonomy to promote motivation is an equally relevant and important need for both genders . SDT has been applied to both boys and girls in physical activity and physical education settings [6–8]. However, there is growing evidence that boys and girls can differ in their interpretations of, and behavioral responses to, the same motivational events and autonomy supportive environments [8, 43]. Despite participating in the same physical education lessons designed to provide autonomy-supportive strategies, girls reported receiving more optimal levels of challenge, autonomy-support and enjoyment; while boys reported greater perceived competence .
Such gender differences in motivational experiences and physical activity responses to autonomy-supportive environmental manipulations may be due to underlying gender differences in usual physical activity participation and previous experiences that have influenced attitudes towards physical activity and decisions to engage in physical activity when encountering such environments. One reason for this gender difference may be baseline physical activity levels. Boys' physical activity under a no choice condition is 30% to 200% greater than girls. Likewise, during periods of unorganized free-play on playgrounds, girls engage in less total and moderate-to-vigorous physical activity than boys [39, 40]. The law of initial values would argue that the greater baseline physical activity of boys would reduce the tendency for their physical activity to increase when provided greater autonomy.
In our previous research (in press, D.M. Feda et al., Journal of Science and Medicine in Sport), when increasing choice from 1 toy to 3 or 5 active toys, boys played with more toys and increased their total physical activity time, yet decreased time playing with their favourite active toy by only 39%. Providing boys with one highly liked active toy is enough to motivate their physically active play. Boys' consistent time of play with their favourite toy effectively dampens the effect of choice on increasing active play time. In contrast, girls' reduced their play time with their most liked active toy 180% when given the choice to play with other active toys, so that choice becomes a salient factor increasing their active play. While the physical activity of many boys is below recommendations, the consistently greater physical activity of boys than girls across environments that vary in autonomy may limit the ability of some boys to increase their activity in environments specifically designed to increase autonomy. As such, autonomy-supportive environments may be less important for motivating boys' than girls' physical activity.
The girls in the present study reported lower enjoyment of physical activity and their enjoyment was positively correlated with their total activity during free-play of traditional active indoor games. Children experience enjoyment when they perform an activity that they are intrinsically motivated to engage in . We did not specifically measure enjoyment of the choice and no-choice conditions, but providing autonomy through choice increased the motivation of the girls to be physically active as measured by an increase in physical activity and consequentially may have made the physical activity experience more enjoyable. If so, such repeated increases in situational motivation could promote increases in contextual motivation , which would encourage future decisions of girls to engage in active indoor play rather than being sedentary when at home.
We hypothesized that the mastery aspects designed into exergames would result in greater physical activity time when no choice was available. Indeed, children played exergames about twice as long as traditional games when only 1 game was available (Figure 1, bottom panel), suggesting that mastery motivated exergame play in the absence of an autonomy-supportive environment. Also, as predicted (Figure 1, bottom panel), an environment that provided both autonomy and mastery was most efficacious at increasing physical activity time. These results are consistent with those of Standage and colleagues  who found that both an autonomy-supportive environment and perceptions of a mastery climate were independent constructs positively associated with mediators (e.g., autonomy, competence, relatedness) of self-determined motivation. Self-determined motivation was then found to positively predict leisure-time physical activity intentions. Likewise, a mastery climate and satisfaction of the need for autonomy, competence, and relatedness were found to independently predict adolescent soccer players vitality for soccer .
Though mastery appears to help motivate children to play exergames twice as long as traditional games, given the differences in movement required to play exergames and traditional games, the energy expenditure of an exergame session may not be greater than traditional games. The current research extends the body of evidence regarding the energy expenditure of exergames by testing differences in the energy expenditure of exergames and traditional home indoor versions of the same games. Previous research has compared the cost of exergames to sedentary games or ergometer-type exercise such as treadmill walking or riding a cycle ergometer [20–28, 46]. It is important to know the physical activity time and energy expenditure associated with exergames relative to traditional active toys in order to determine the implications of their use as an alternative to traditional active play. Though children in the current study played exergames twice as long as traditional games, this was off-set by the energy expenditure during play of exergames being approximately one-half that of traditional games. Thus, children must play exergames twice as long to match the energy they would have expended during traditional indoor play. Most of the exergames tested produced only small increases in energy expenditure above rest. Many exergames can be played using one arm and with little movement of the lower limbs. Exergame play requires movement of both upper limbs and the lower limbs to effectively increase energy expenditure [47, 48]. An area for future study is to determine which types of activities exergame play replaces. If exergames replace traditional active play, that could result in a reduction in MVPA given that children participated in 142% greater MVPA when playing with traditional active toys than exergames. On the other hand, if exergame play displaces what would otherwise be sedentary videogame play or other sedentary behaviours, then even the light intensity physical activity of exergames would increase energy expenditure.
The basic laboratory data reported here add to the development of future intervention studies. The results suggest that incorporating aspects of both autonomy and mastery into a physical activity program may be best at increasing childrens' intrinsic motivation to participate in physical activity. Such a program may be most efficacious for girls, in particular, and may do so by making the exercise sessions more enjoyable.
This study is not without limitations. The children were tested alone. Typically play is a social behaviour, and children may have felt the isolated play environment was artificial. Children may have changed their total minutes of play, intensity of play or toy choices if they had been given more space or had a friend to play with. However, the traditional and exergames used to promote physical activity in the indoor laboratory setting were designed for indoor use and to be played either alone or with a peer or parent. Still, these are interesting questions for future research. The study was not powered to detect interaction effects of the energy expenditure data. Such results should be interpreted with some caution. Moreover, the small subsample size used to test differences in energy expenditure of exergames and traditional versions of the same games may limit generalizability.