Sedentary Behaviors in Children and Adolescents: What Is the Influence on Bone Strength?

Whether driving to work, sitting in the classroom or office, or watching TV, sedentary behavior is commonplace in modern society. This is especially true for children and adolescents who, behind older adults, spend the largest proportion of their day being sedentary. Evidence linking excess sedentary behavior to increased adiposity and cardiometabolic risk in youth has contributed to the adoption of guidelines advising the restriction of behaviors such as TV viewing in several countries. However, evidence is limited concerning the effects of sedentary behaviors on bone strength, especially during adolescent growth, the period of peak bone mineral accrual. A recent review concluded that a negative association exists between sedentary behavior and bone mineral accrual in the lower extremities. In contrast, longitudinal data in adolescents highlighted positive relationships between sedentary behaviors and some aspects of bone microarchitecture. Regardless of the direction of the relationship, findings appear to be independent of time spent in moderate-to-vigorous physical activity (MVPA). While it is premature to generate public health recommendations with respect to sedentary behaviors and bone, it is clear that MVPA remains the most influential activity-related behavior for optimal bone accrual. Future guidelines should continue to promote activity while examining its interaction with sedentary behaviors.