Results from this study indicate that earlier timing of pubertal development at age 11 is associated with lower levels of physical activity at age 13. This relationship remained after controlling for body fatness, self-reported physical activity, and family SES at age 11. Consequently, the identified associations are not driven by preestablished levels of physical activity (ie, low-active girls maturing more quickly than high-active girls) or body fat (ie, girls who are more overweight and more sedentary going through puberty earlier than their leaner peers). These findings indicate that early-maturing girls are at an increased risk of physical inactivity during adolescence and that additional research on possible factors explaining this association is warranted.
Early pubertal timing combined with low levels of physical activity may place girls at particular risk of negative health outcomes Previous research indicates that early pubertal maturation is linked with negative mental and physical health outcomes such as poor body image,28
and increased breast cancer risk.30-32
Physical inactivity is also a risk factor for negative health outcomes such as obesity,33
and lower levels of social functioning.39
Drawing together these 2 bodies of research suggests that early-maturing girls who are inactive may experience compounded risk for negative health outcomes. The possibility of increased risk among early-maturing girls provides further justification for research on mechanisms linking early maturation and physical inactivity and ways to promote physical activity in this high-risk group.
Early pubertal maturation may lead to low physical activity for a variety of reasons including both intrapersonal factors (eg, body esteem, depression, and perceived skill) and interpersonal factors (eg, parent and peer support). With regard to intrapersonal factors, early-maturing girls have been found to have poorer body image than their later-maturing peers,40
which has been identified as a constraint to both participation in and enjoyment of leisure activities.41,42
Earlier-maturing girls may be reluctant to participate in physical activity in settings they believe draw attention to their bodies. Higher levels of depression exhibited by early-maturing girls37
may also decrease girls' motivation for engaging in physical activity. In addition to decreasing girls' motivation for physical activity, the physical changes of puberty may impact girls' ability to participate in physical activity. For example, breast development may directly reduce spontaneous physical activity because of the need for appropriate clothing. Furthermore, puberty-related changes put girls at a performance disadvantage in some sports.43
As a result, earlier-maturing girls may self-select out of sports because they are less skilled than their later-maturing peers.43
Early-maturing girls may also decrease their physical activity during adolescence as a result of changes in interpersonal factors such as interactions with parents and peers. Parent-daughter relationships change significantly during puberty. Parents, particularly fathers, may be uncomfortable with the changes in their daughter's body.44
Along similar lines, early-maturing girls report that adults expect them to behave more maturely.44
This combination of parental discomfort regarding their daughter's more mature body and their tendency to encourage more adult behaviors may result in parents providing less support for “childlike” activities such as playing outdoors and more encouragement for less physically strenuous activities that are perceived as more feminine. Although parental support is important throughout childhood and into adolescence,45
peers become increasingly influential during this developmental period.46
Research shows that earlier-maturing girls tend to associate with an older peer group.47
Given the general decline in physical activity with age in adolescence,48
earlier-maturing girls are likely to belong to a peer group that is less active than their age cohort. In sum, there is a broad range of factors that may explain the link between pubertal timing and physical activity, including intrapersonal and interpersonal factors that warrant future investigation.
This study has a number of strengths. The longitudinal design of the study allowed the examination of the effect of pubertal timing among young adolescent girls (at age 11) on their physical activity levels 2 years later (at age 13) controlling for physical activity levels at age 11. Additional strengths include the use of multiple measures of pubertal development to classify pubertal timing and the use of an objective measure of physical activity. There were also several limitations. Participants in the study were primarily white girls residing in central Pennsylvania. Therefore results may not generalize across geographic areas or ethnicities. It is possible that very different associations would be identified between pubertal timing and physical activity among other ethnic groups given ethnic differences in pubertal timing,49
ideal body shape,50
and baseline physical activity.1
An additional limitation is the use of a self-report measure of physical activity at age 11 (objective monitoring was not available at age 11) for which relatively little measurement work has been done. Differences in physical activity between earlier- and later-maturing girls may have existed at age 11, but the self-report physical activity measure may not have been sensitive enough to detect them. Finally, the measurement of pubertal development resulted in limitations. Because of the limited age span that was assessed, it was not possible to separate the effects of early pubertal timing from pubertal development per se. In addition, because 2 of the 3 variables used to measure pubertal status were not assessed at age 13, potential relationships between tempo of pubertal timing and physical activity could not be explored.
Although results from this study do not directly speak to the mechanisms that may lead early-maturing girls to disengage from physical activity, they highlight that early-maturing girls are at risk of low physical activity. Individuals interacting with adolescent girls such as doctors, teachers, parents, and coaches should be aware of this fact and seek ways to maintain girls' interest in physical activity as they transition through puberty.