Selection shaped us to be endurance athletes…AND couch potatoes!

“Is Exercise Really Medicine? An Evolutionary Perspective:”
By Daniel E. Lieberman
Current Sports Medicine Reports 14, no. 4 (2015): 313–19.
Click here for the open access pdf

This superb short evolutionary analysis of the role of exercise in human health should be required reading for everyone interested in exercise and health…that is, all health professionals, and most of the rest of us us.  Lieberman shows that we were shaped to be endurance athletes by the benefits of chasing big game animals until they could go no further. But our ancestors also faced intermittent calorie shortages that shaped mechanisms to minimize unnecessary exercise, and to shrink unneeded tissues. Extensive daily exercise was so intrinsic to human life that the health benefits of exercise were never a selection force.

Several quotes offer eloquent summaries:

“The many mechanisms by which physical inactivity increases the risk of chronic, noninfectious diseases do not occur because physical activity evolved as an adaptation to prevent ill health, but instead, they evolved as adaptations to prevent excess capacity in individuals who were already active but energy limited.”  For instance, muscle loss conserves calories. (p. 317)

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 “While exercise is an effective prescription to promote health, there is no minimum dose, no optimal dose, and no dose without risks or negative consequences.” (p. 313)

‘While physical activity is unquestionably a potent medicine, it never evolved for that role. Instead, humans’ evolutionary legacy as physically active endurance athletes on the margin of energy balance has resulted in a myriad of adaptive dose-response relationships in which the body uses stimuli from physical activity to adjust capacity to demand in order to maximize reproductive success. In addition, a chronic absence of moderate physical activity was so rare until recently that, from an evolutionary perspective, such levels of inactivity are not only abnormal but also cause pathology”  (p. 317)

In short, selection shaped us to be couch potatoes whenever possible, which now is almost always. And, the pathways from sedentary life to ill health are mostly adaptations that were useful for our ancestors, but often fatal today. Buy cymbalta 20mg

Abstract

An evolutionary perspective helps evaluate the extent to which exercise is medicine and to explain the exercise paradox: why people tend to avoid exercise despite its benefits. Many lines of evidence indicate that humans evolved to be adapted for regular, moderate amounts of endurance physical activity into late age. However, because energy from food was limited, humans also were selected to avoid unnecessary exertion, and most anatomical and physiological systems evolved to require stimuli from physical activity to adjust capacity to demand. Consequently, selection never operated to cope with the long-term effects of chronic inactivity. However, because all adaptations involve trade-offs, there is no evolutionary-determined dose or type of physical activity that will optimize health. Furthermore, because humans evolved to be active for play or necessity, efforts to promote exercise will require altering environments in ways that nudge or even compel people to be active and to make exercise fun. zovirax 400mg