Bryce Harper doing squats while standing on an exercise ball shows how ridiculously fit professional athletes can be

Nick Wass/AP

It can be easy to forget how immensely, freakishly fit professional athletes are when you watch them perform stunning feats in a game.

Dunking from the free-throw line, bombing a 50-yard pass, throwing 90 mph, etc. - it can all be blurred, particularly when seeing it through a screen.

So, every now and then, the best reminder that these are all physically gifted humans can be through their behind-the-scenes preparation for those on-field feats.

Bryce Harper gave a look at that preparation on Friday by posting an Instagram video of himself doing squats while balancing on an exercise ball. On the surface, that doesn't sound otherworldly difficult, but video of the workout proves otherwise:

Doing anything on an exercise ball is difficult, let alone balancing on one. Note the difficulty with which Harper, one of the best baseball players in the world, is doing those squats. Normal humans can't do this.

So the next time Harper blasts one out of the park, remember that it is not easy to do, and that one can't achieve it without equally difficult off-field work.