The burpee. It's the humble, almost silly sounding exercise that, in reality, is one of the most effective and most efficient, but also the most feared moves, in all of fitness. A punishing full-body exercise that everyone from pro athletes and CrossFit addicts to elite military forces swear by. Here's why: the high-intensity combination involves strength training, endurance building and fat burning in one relatively simple maneuver. It fires up many large muscle groups throughout your whole body—from your glutes and quads to your abs, chest and shoulders. And they're all engaged in a very intense, very kinetic way simultaneously.

Best of all, it requires nothing but sheer will and determination. Invented in 1939 by physiologist Royal H. Burpee as a way of testing one's fitness levels, he used the exercise as his thesis for a doctorate from Columbia University. The military soon adopted it as part of its fitness test for men enlisting during World War II.

Over the past eight decades, the burpee has evolved into an intense multi-move exercise that delivers three times the benefits of standard moves like jumping jacks or push-ups. And since they require a lot of energy and increase your respiration, you enjoy the “afterburner effect” long after you're finished, which continues revving your metabolism and burning calories.

There's something else too. You not only feel physically strong when you do them, but mentally powerful as well. Perhaps it's because they work the whole body, or simply because they are somewhat difficult to do, but you feel accomplished and ready to tackle anything when you're done. Plus, you don't need to do that many to see some real benefits. To get you started, here's how to master the gold standard, along with four worthy variations to work into your routine.