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Rest too long after an injury and your system powers down, preparing you for a peaceful exit. Fight your way back to your feet, however, and you trigger that magical ON switch that speeds healing hormones to everything you need to get stronger: your bones, brain, organs, ligaments, immune system, even the digestive bacteria in your belly, all get a molecular upgrade from exercise. For that, you can thank your hunter-gatherer ancestors, who evolved to stay alive by staying on the move. Today, movement-as-medicine is a biological truth for survivors of cancer, surgery, strokes, heart attacks, diabetes, brain injuries, depression, you name it.
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Christopher McDougall (Running with Sherman: How a Rescue Donkey Inspired a Rag-tag Gang of Runners to Enter the Craziest Race in America)