Shredders, Up-Downs, Squat-Thrusts, Mother-F—ers…; there are lots of names for them, but in CrossFit we call them Burpees. And no matter what you call them they are simultaneously among the most reviled yet most effective exercises for building metabolic conditioning. They might not look like much but remember you are moving your body’s center of mass three feet with each rep. That’s no joke. Put them in your routine TODAY! Here’s how to do them properly.