Bone strength and physical activity over the lifecourse

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

There are a number of genetic, behavioral and life history factors associated with bone mass in the modern human skeleton. Previous research in animal models, and in human clinical and archaeological samples, has shown a positive relationship between physical activity and bone mass. However, few data are available for population-representative samples from modern human groups with very high activity levels and pathogen loads. This project will study bone mass in such a population, in order to advance our understanding of the complex relationships among bone mass, population history, energetics, and physical activity across the lifespan. The proposed research will advance our understanding of modern human skeletal evolution and adaptation, as well as the skeletal impacts of the sedentary lifestyle found in many industrialized societies including the U.S. This project will provide training opportunities for graduate and undergraduate students, support international research collaborations and public science outreach activities, and contribute bone-related data to a larger ethnographic and biological database for a non-industrialized population. Physical inactivity, relative to past populations, is thought to contribute to modern human skeletal gracility, based on the idea that impact forces from load bearing and muscle contraction trigger bone deposition, a process called "bone functional adaptation." According to this idea, which is well supported by studies of athletes and exercise interventions, bone adapts to the demands of physical activity both by adding bone tissue and altering its cross-sectional distribution in the direction of the highest bending strains. However, anthropological studies of bone functional adaptation have not fully explored the potentially interactive and/or confounding effects of activity profiles, diet, infectious burden and body composition (e.g. muscle mass) on bone. This project will test whether higher physical activity levels, including in childhood, lead to greater bone strength, and whether greater bone strength mitigates age-related bone loss and fracture risk. The project will also examine the extent to which bone growth in response to habitual, physically-intensive subsistence activities is constrained by energetic limitations and high pathogen burden. To address these questions, the research team will 1) image arm and leg bone structure using quantitative computed tomography (pQCT) of the tibia, femur, radius and humerus; 2) measure physical activity levels to examine effects of mechanical loading on bone structure; 3) examine how degree of industrialization, family history of fractures, and socio-economic factors impact the relationship between physical activity levels and bone strength; and 4) document prevalence and structural correlates of low bone mass. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.