Doctoral Dissertation Research: Evolutionary mismatch and variation in physical activity and function

Harvard University, Cambridge MA

Investigators

Abstract

Humans evolved to be moderately physically active, walking longer distances daily than many are currently used to, often while carrying things, and engaging in many other subsistence-related tasks that involve bodily movement. Regular physical activity (PA) is such an important part of the human environment that its prolonged absence increases the risk for numerous diseases and conditions including lower back pain (LBP), the most common musculoskeletal condition in the world. Although many factors contribute, the strongest predictor of LBP is the endurance of trunk muscles. The endurance of trunk muscles and spine loading depend largely on how much and what types of PA a person routinely engages in. To better understand how PA affects the trunk and spine function, this Doctoral Dissertation Research project studies people engaging in high levels of PA such as walking long distances each day and consistently engaging in manual labor, often while carrying water, food, and infants, compared to people with more sedentary daily activity levels. The project provides research training and collaboration opportunities for local community members and researchers. The primary hypothesis tested by this project is that reduced PA generates low levels of trunk muscle activity and spinal loading which are associated with low trunk muscle endurance. To test this hypothesis, novel wearable sensors that measure bodily movement and back muscle activity are combined with computer-based musculoskeletal modeling to compare spinal loading and back muscle activation levels between rural (high-activity) and urban (low-activity) populations to assess whether differences in spinal loading and back muscle activation levels are associated with trunk muscle endurance. The project also uses wearable sensors to test how trunk muscle endurance affects two spine functions hypothesized to be associated with LBP: modulation of spine stiffness during walking and the distribution of compression and shear forces generated in the spine during walking. By making use of a research design where two populations with different PA profiles live in geographic proximity, this project addresses why and how engaging in PAs at different levels may help our bodies, and specifically our backs and spines, function better and stay LBP-free. Ultimately the results of this research can contribute to our understanding of how our modern activity levels may be a mismatch for the levels of activity experienced throughout human evolution. 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.