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Background: This study investigated associations between different types of sedentary behavior (SB) and physical activity (PA) in parent and their child, including the moderating effects of parent and child sex. Methods: In total, 1231 adolescents, 1202 mothers, and 871 fathers were evaluated. The SB (TV viewing + computer + video game); different types of PA (leisure-time PA, occupational PA, and total PA); and the socioeconomic level were evaluated by questionnaire. The relationship between adolescents’ SB and PA with parental characteristics was estimated by linear regression. Results: The SB of male adolescents was correlated to the father’s SB (β = 0.26; 95% confidence interval [CI], 0.13–0.39) and mother’s SB (β = 0.18; 95% CI, 0.06–0.31). A similar relationship was observed between SB of female adolescents and the father’s SB (β = 0.31; 95% CI, 0.19–0.42) and mother’s SB (β = 0.29; 95% CI, 0.20–0.38]). The SB of girls was inversely related to mother’s occupational PA (β = −2.62; 95% CI, −3.66 to −0.53]). The PA of the boys and girls was correlated with their fathers and mothers PA. All the results were adjusted for age and parent’s socioeconomic level. Conclusions: SB and PA of parents were associated with SB and PA of their children, regardless of gender. Strategies for health promotion should consider the family environment to increase PA and reduce SB.

Training load had a negative relationship on bone density of swimmers of both sexes, independently of the positive effect of lean soft tissue on bone density.

The objective of the present study was to investigate the effects of different sports on stress fractures among adolescents during a 9-month follow-up period. The sample was composed of 184 adolescents divided into three groups (impact sports [n = 102]; swimming [n = 35]; non-sports [n = 47]). The occurrence of stress fracture was reported by participants and coaches. As potential confounders we considered age, sex, resistance training, body composition variables and age at peak of height velocity. There were 13 adolescents who reported fractures during the 9-month period. Bone mineral density values were higher in adolescents engaged in impact sports (P-value = 0.002). Independently of confounders, the risk of stress fracture was lower in adolescents engaged in impact sports than in non-active adolescents (hazard ratio [HR] = 0.23 [95% confidence interval (CI) = 0.05 to 0.98]), while swimming practice was not associated to lower risk of fracture (HR = 0.49 [95% CI = 0.09 to 2.55]). In conclusion, the findings from this study indicate the importance of sports participation among adolescents in the reduction of stress fracture risk, especially with impact sports. More importantly, these results could be relevant for recognising adolescents in danger of not reaching their potential for peak bone mass and later an increased risk of fractures.