New Frontiers in Endurance Exercise Biology
Give every individual the right amount of exercise, not too little and not too much.1
Physical activity has long been tied to good health. Hippocrates was guided by his theory of balanced humors to advocate that absolutely everyone, young or old, needs exercise, but not too much. A landmark 1953 study noted that drivers of public trolleys in London had twice as many acute coronary syndromes as did conductors of the same trolleys, the only notable difference being that conductors walked as they collected tickets and drivers sat.2,3 In the decades since this seminal epidemiological observation, nearly every aspect of human physiology has been demonstrated to benefit from exercise, ranging from lung and cardiac function to cognition and aging (Figure 1). The same decades, however, have witnessed a dramatic sedentarization of the US population (despite the newfound popularity of recreational exercise). Today, the consequences of sedentary lifestyles, synergizing with dramatic increases in caloric intake, are ubiquitous and devastating.
Exercise is a fundamental component of the human condition. Humans are the only primates capable of sustained long-distance running, and this behavior likely significantly shaped the evolutionary departure of humans from other primates.4 For example, the need for heat dissipation during prolonged physical activity likely favored loss of body hair and the proliferation of sweat glands, thereby considerably altering the human form.5,6 Endurance exercise thus not only is good for us but in fact is part of what defines us. Not surprisingly, the study of exercise, including its mechanics, physiology, and health benefits, has long garnered fascination. Over the last decade, new molecular techniques have ushered in a new era of exercise research, focused on understanding fundamental mechanisms. The wealth of new information is staggering. …