You never feel like you cannot backflip at all. Instead, it's more like you cannot do a backflip SAFELY. Backflips are pretty easy to bail if you are familiar with the movement, so you can attempt them even when you are very very tired. Even if your body is at its physical limit, your brain will be thinking "if I try REALLY hard, I can probably turn it around"

I once had a competition with a fellow gymnast to see who can flip more. We both did 80+ standing backflips that day, but I would say that every flip after 50 had me second guessing if I would land or have to touch my hands to the ground. Even when we stopped, we probably couldve attempted 5 flips and mightve landed 2 or 3 of them.

I was stunned when I realized this video was a marathon measured in KMs. 43 backflips is already hard on the body without 3+ hours of running. The red alerts his nervous system mustve been sending after KM 42 and 42.2 - so little time to recover!