[alexpw]

+1 "mobility you probably do not have"

Poor posture, tight hamstrings, weak ankles, knee joints, tendons, etc. You can't take those things for granted.

The more complex the movement, the more likely you are to involve a part of the body that is not capable of handling it. Other parts will compensate, but if you go to failure or use imperfect form, you'll quickly discover a weak link.

Complex movements are the best for maximizing strength gains, but even without weights, they can more easily break you.