Teun Remmers

Relationship between PA enjoyment and PA in children | 35 Introduction Effects of interventions that attempt to increase children’s physical activity (PA) are often limited to short-term improvements. A child compensating intense PA with more sedentary behavior is a major paradox in these studies (1). In contrast, determinants of long-term, self-sustained, habitual PA behavior may give insight in how long-term increases of self-sustained PA are most likely to be achieved. Enjoyment of the activity itself, instead of external pressure or rewards, is a key prerequisite of intrinsic motivation, which is in turn related to habit formation and self-sustainment (2). Therefore, PA enjoyment may be an important determinant of long-term habitual, self-sustained PA behavior in children. Increments in this type of PA may provide beneficial effects to cardio respiratory, musculoskeletal, and morphological aspects of children’s physical fitness. Studies that examine the relationship between PA enjoyment and PA behavior can reinforce theoretical frameworks of future observational studies and PA interventions. Few studies previously investigated relationships between PA enjoyment and children’s PA behavior (3-8). Subjective measurements of PA (e.g. parental reports) are prone to significant measurement errors in children (9), as children’s PA behavior is considered less structured (e.g. short bouts of intense PA) and shows considerable daily variation compared to adults (10). We identified only two studies that examined PA enjoyment in relation with objectively assessed PA behavior (i.e. accelerometers) (3,5), and their results are contradictory. While Wenthe et al. (2009) found that PA enjoyment was related with PA behavior in adolescent girls, Lawman (2011) found no such association in 11 year-old underserved boys and girls. The ecological perspective of heath behaviors and several social-environmental models purpose that the influences of social environmental factors depend on personal characteristics (e.g. age, gender) and physical environmental factors (e.g. accessibility) (11,12). Thus, for a better understanding of the influence and implications of PA enjoyment on PA behavior, personal characteristics that may moderate the relationship between PA enjoyment and PA behavior are of interest. First, gender differences may be important, as objective measurements showed that girls are generally less active (13,14) and girls display a considerable decline in activity energy expenditure before puberty (10). One study found that gender differences in determinants of PA (e.g. family support, physical access, crime) were indeed related with gender differences in objectively measured PA (3). In addition, boys have different PA preferences than girls, with boys preferring more high intensity activities (15), potentially leading to differences in participation of especially high intensity PA. However, it is unknown whether these gender differences may also exist in PA enjoyment because PA is assessed across various exercise and PA modalities. Second, several studies reported patterns of decreased PA while children get older (14,16). These age -related PA declines are especially worrisome if maintained over longer periods of time and a sustainable determinant of PA (i.e. PA enjoyment) may predict this long-term development of child PA (17). Age may attenuate the association between PA enjoyment and PA behavior in a way that older children may