Is it bad to be completely winded after digging a 4 inch deep, 2 ft by 8 ft hole?

Decided to try gardening as an activity I can do from my wheel chair. Haven't exercised much and no rototiller so have to dig my first bed up by hand. Going to be a multi day process, a few inches at a time. These first few days are going to be the roughest, punching through all the roots. Don't help that I waited for it to be 90 degrees out to get started.

Assuming my poor heart doesn't explode, I suppose it'll be good exercise at least