The muscle-up is a rare beast – an upper-body exercise that requires both pulling and pushing power and phenomenal core strength to boot.
Those unfamiliar with the move say it's just a pull-up combined with a dip, but a muscle-up is much more than that. It's an unparalleled assault to the upper body, and you have to be strong just to do one.
It's a fact: the exercises that make you hate life the most also tend to deliver the best results. If you're in serious need of a hamstring overhaul, then this article is a great (although painful) place to start.