When you move in unison with other people, particularly when it's to music, there are a couple of hormones and neurotransmitters that increase. Endorphins [are] the big one, and endorphins are part of what make you feel so good. But endorphins are also a bonding hormone ... It also increases oxytocin, which is a hormone that helps us feel close to other people and form these social bonds. And oxytocin also has the side effect of dampening down fear and anxiety. So, we start to feel braver, and we start to feel more optimistic.

There are all sorts of other explanations for why someone who struggles with addiction might benefit from things like running or ultra-endurance training ... These endurance training activities—running, swimming, hiking, biking—they seem to work like an antidepressant. And they seem to also reverse some of the brain changes you see after addiction; they restore the brain to be better able to resist impulses and cravings and also experience pleasure.

"If you're someone who doesn't run and you start a running program, one of the ways that the brain changes is it actually increases the binding opportunities for endocannabinoids and dopamine—these two chemicals in your brain that make you feel optimistic, that make you feel happy, that make you feel like everything is right in the world.

As people age, in general, they seem to lose 13% of their dopamine receptors ... That may explain why a lot of people, as they age, they seem to enjoy life less. And there also is an increased risk of depression...

I wanted to understand why people who exercise regularly are happier in every way. And beyond just they're in a good mood when they exercise, but it's things like: they have more meaning in life, and they're less lonely; they feel more gratitude.

...You will get so much more out of whatever movement form you're doing if you can separate it from the desire to make yourself look a certain way.