Collaborative Research: The Evolutionary Biology and Health Consequences of Human Inactivity

Cuny Hunter College, New York NY

Investigators

Abstract

Recent research has associated sedentary living, and specifically, long periods of Western-style chair-sitting, with high levels of cardiovascular disease (CVD), suggesting that such behavior may be an important component of elevated rates of CVD-related morbidity and mortality in Western society. This increased risk has been attributed to a sitting-induced reduction in lower limb muscle activity, with concurrent decrease in the production of enzymes that siphon fat from the blood stream. Individuals in other cultures also are often inactive for long periods of time, yet do not seem to develop the same risk of CVD. It therefore is possible that styles of resting are more important than time spent sitting, and that people in other societies rest in ways that maintain muscle activity and thereby reduce cardiovascular disease risk. For example, it may be that squatting, potentially requiring levels of muscle activity similar to standing, is a prominent form of resting posture in non-Western societies which can be related to enhanced cardiovascular health. And as such resting behavior may have similarly characterized early human ancestors, the health costs associated with alteration in forms of resting posture also may have an evolutionary basis. This research tests the hypothesis that the style of sitting in non-Western societies increases muscle activity and improves blood lipid profiles compared to Western-style sitting, thereby promoting beneficial health effects. Initial testing of this hypothesis will entail a field study of contemporary human hunter-gatherers (the Hadza people of Tanzania) in order to examine styles of rest and inactivity in traditionally-living humans. Second, focusing on a population of subjects experienced in squatting, a randomized crossover experimental design will be employed to measure muscle activity and changes in blood lipids following prolonged periods of squatting versus chair-sitting. Using these methods, the research will explore the evolutionary and contemporary human biology of resting postures in the context of health and well-being. As the first study to explicitly examine human inactivity from a cross-cultural and evolutionary perspective, this project will transform our current understanding of how more sedentary lifestyles impacted functionality of modern human physiology. And in the assessment of the impact of such behavior on human biology relevant to disease and mortality rates in the US, this work also could find translation into behavioral interventions which improve public health in Western societies, as well as application in societies undergoing transitions to more Western-style inactivity patterns.