Early Pubertal Maturation Among Adolescent Girls Is Associated with Lower Subsequent Physical Activity

Abstract

PURPOSE: To examine the relationship between pubertal timing and physical activity in adolescent girls. METHODS: Data were collected from a longitudinal sample of 186 girls at ages 11 and 13 years. Independent variables assessed at age 11 included pubertal development, Body Mass Index (BMI) z-score, and self-reported physical activity. Dependent variables assessed at age 13 included self reported and objectively measured physical activity. Direct observation of breast development using Tanner staging was used to assess level of pubertal development. Scores of 3 or higher were classified as early pubertal maturation (EM; 30% of sample) and scores of 1 or 2 were classified as non-early maturation (NEM). Measured height and weight were used to calculate age and sex adjusted Body Mass Index z-score using the CDC 2000 growth charts. Self-reported physical activity was assessed using the Children's Physical Activity scale and a questionnaire assessing sport participation. At age 13, average daily minutes of vigorous physical activity (VPA) and moderate to vigorous physical activity (MVPA) were objectively measured using the ActiGraph accelerometer. RESULTS: Results from t-test analysis showed that, relative to NEM girls, EM girls had significantly lower self-reported physical activity (NEM mean =2.84 ± .41; EM mean=2.67 ± .38; t = 2.39, df = 153, p=.02) and marginally lower objectively measured VPA (NEM mean = 5.48 ± 4.43; EM mean= 3.48 ± 3.73; t= 1.86, df= 57, p= .07) at age 13. RESULTS: from multiple regression analyses, controlling for self-reported physical activity and BMI z-score at age 11, showed that EM girls had significantly lower self-reported physical activity at age 13 than NEM girls (β = −.21, p<.01). For the girls completing accelerometry (n=59), EM status was inversely associated with objectively measured MVPA (β= −. 13, p =.34) and VPA (β= −.20, p=.15); however, due to the smaller sample size, these effects were not statistically significant. CONCLUSION: Early maturation is associated lower subsequent levels of physical activity in girls. Lower levels of physical activity among EM girls may help to explain the negative physical and mental health outcomes associated with EM status among girls. Supported by NIH Grant RO1 HD046567 and RO1 HD32973 and MO1 RR10732