Self-generated optic flow from activities like walking, biking, or swimming is beneficial for the visual system, mood, and neuromodulator systems.

“When you move through space, whether or not it's through walking, biking, even swimming, if it's self-generated optic flow, so probably not driving or motorcycling, but yes, bicycling or I don't know, unicycling. ... As long as it's self-generated optic flow, meaning you're generating motion of your body and the visual images around you are passing by on your eyes, that is very good for the visual system. And it's very good for the mood systems and the neuromodulator systems of the brain and body that regulate mood.”