You probably know where I am going with this, but look at that picture for a minute. Now imagine that this was one of your staples - a staple which you HAVE to tackle, simply to eat. Now imagine yourself going out on the hunt, to kill on of these animals......!
Given the scenario above and the physical prowess of the woolly rhino, what kind of physical skills do you think you would want to possess prior to going in to battle with one? Obviously you'd want speed and agility to get close to it, but also to keep out of its way. You'd want great strength to throw spears or rocks into it. Your movements would involve multidirectional bursts of speed, changing angles quickly as the 'battle' dictated.
What of the 'crash'? Perhaps you might need to quickly scale rocks or a tree if the wider herd were in pursuit. For sure, you would probably choose not to 'jog' away in a steady state.
Perhaps you would be called upon to rescue an injured comrade?
Even after kill, you might be called on to protect your kill from other scavengers. The meat would have to be quickly butchered and carried back to camp. The load would be heavy.
Modern Gym Rats
Think about your local gym. Can you imagine a bodybuilder or even a power lifter expressing the necessary qualities to engage in those activities above?
More importantly, does YOUR workout?