it effectively turned sedentary 55-year-olds into 30-year-olds when viewed through heart activity monitoring equipment.
Being that heart disease is the leading cause of death for most people in the United States, and cardiac strength is inversely correlated with heart disease, it’s probably one of the most significant studies on exercise ever carried out.
Then your imagination is evidently limited.
To feel tired you need your body to exhaust itself, which makes you feel like shit. To exaggerate my point a little bit here for better understanding: It’s the very act of movement that causes it. It doesn’t matter how you do it, the body immediately tells you it’s shit once it has to ramp up everything to deal with the strain and will keep doing so making sure you only do things as much as necessary (like to catch a bus, ride a bicycle to your important destination etc).
Like I said before, the only way this makes any sense to me is that your brains, for some reason, react to this willful suffering with blasting out dopamin and stuff. Otherwise it doesn’t make any sense to me why and how so many people deal seem to hurt themselves without going nuts.
The body is clearly stressed by exercise, I hope we can agree on that as smallest common denominator?