Active Growth, Active Life: Eliminating Biomechanical Barriers to Physical Activity through Growth-Period Exercise

PROJECT SUMMARY Physical inactivity is a grave public health concern as a primary contributor to disease and mortality that also imposes a massive burden in terms of health costs. Addressing these problems requires the removal of barriers to physical activity, including biomechanical barriers originating within our own bodies. Humans and non-human animals alike are more active in adulthood when they have had a more active childhood, but the reasons for this are not well understood. We propose that physical activity during childhood promotes healthy development of musculoskeletal structure that reduces the effort associated with movement, thus predisposing adults to physical activity throughout their lifetimes. Previous work, including our own recent studies using an avian animal model, supports this idea: The structure of muscles and bones has been shown to adapt to loading that accompanies activity, and this plastic adaptation is especially pronounced during the growth period. Further, there is evidence that animals with limited early-life activity have altered muscle mechanical advantage and exhibit less spontaneous activity as adults. The purpose of the work proposed in this R01 application is to explore these connections between structure, function, and behavior using a rigorous multi- level experimental approach that spans tissue-level analysis, locomotor analysis, and behavior analysis in avian (guinea fowl) and mammalian (mouse) animal models, each of which offers distinct advantages. Specifically, we will: (1) investigate the dose of early-life exercise necessary to produce lasting changes in musculoskeletal structure, locomotor function, and adult behavior; (2) study the effects of the timing of exercise onset in childhood on these outcomes; and (3) examine whether there are special benefits for early-life physical activity in relation to adult-onset exercise. If successful, this work will change our understanding of the factors influencing physical activity behavior, directly informing new interventions that improve activity-related health throughout the lifespan.