Years ago, when David Raichlen got back into distance running, he noticed a swift improvement in his mental health. “This doesn’t make sense,” he thought. “Why would purposefully engaging in energy output for no reason make me feel good?”
It’s not what most humans would have likely wondered after experiencing what’s colloquially known as runner’s high. But Raichlen is an evolutionary biologist and professor at the University of Southern California. He knows the intricacies of how the human body evolved to conserve energy, rather than waste it.
It would make more sense, he thought, if exercise left people feeling crummy. That way people would only move for crucial reasons, like securing nourishment. To the contrary, however, cardio seems to release a cocktail of brain molecules that lift moods, reduce anxiety, blunt pain and leave people feeling euphoric.
On top of that, we now know exercise improves overall brain health — enhancing the formation of new brain cells as well as the regeneration of myelin (the sheath that insulates nerves). For people with low to moderate depression, it has also proven to be as effective as antidepressants in numerous trials.
