henry copeland: Evolution selects for atrophy to conserve calories, says Harvard's Daniel Lieberman. pllqt.it/UMzc8u
Why is exercise hard? | Harvard MagazineThis tension between activity and rest, he says, plays out in human physiological and anatomical systems that “evolved to require stimuli from physical activity to adjust capacity to demand.” Muscles become bigger and more powerful with use, for example. With disuse, they atrophy. Bone deposition and repair mechanisms likewise require the presence of mechanical stimulation, such as running. The absence of such stimuli can eventually lead to a risk of osteoporosis. “In the circulatory system,” Lieberman continues, “vigorous activity stimulates expansion of peripheral circulation,” improves the heart’s ability to pump blood, “and increases arterial elasticity.” Without exercise, arteries stiffen, the heart pumps less blood, and metabolism slows. All of this “downregulation” of biological systems evolved to conserve energy whenever possible.