"During low- to moderate-level exercise, the body harnesses energy from a molecule called adenosine triphosphate, or ATP, which uses oxygen in the body to keep you moving. Staying at this intensity level allows you to work out while also effectively recovering afterward.
When your regimen is too strenuous, however, the demand for ATP is higher, and it can leave your energy reserves depleted and may leave you with extreme fatigue after working out."
"too strenuous" they call it.
i call it home.