I've heard it all now.
Maybe Sprints is how Ondra has been getting so strong - no one would have guessed, sneaky!
This is the mother of all generalizations.
First of all, Ondra isn't strong. And even if he were, he surely became so by climbing full on, full time, from the age of 6 or so.
This doesn't mean that we, mere mortals, can't benefit from some extra work to be added to the deadhangs, system, bouldering and PE that we already do.
If I had time, I'd also lift heavy, but while a gym session needs at least a couple of hours, with sprints I was done in 30 minutes, warm up included.