I”m pretty sure endorphins may play a part. I do remember playing high school and trying out for college football..there was no pain during games or practice...just about 2 hours after the pain would start.
Just think athletes are experiencing the positives effects of those chemicals without the nasty central nervous or peripheral side effects of thc and opiates..and it makes you healthier and it is legal.
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>>it makes you healthier
Yep. Earning the reward response as nature intended provides the benefits of the associated physical activity. It’s not all that complicated.
But, OTOH, there’s Mr. Phelps - who figured out it could help him expand his limitations (which I still think is cheating).
Be interesting to see if related consequences arise for him down the road.