Lying on your back and thrusting your pelvis in the air is generally reserved for... things covered by other magazines. So you're not alone if you feel a little awkward doing glute bridges with an audience.
Why you should do it: Thanks in part to the position of our eyes, exercises that slim and tone the front of the body (hello, abs!) get a lot of attention. But for optimal health and fitness (and to look and feel amazing in your skinniest jeans) your posterior need just as much love. This exercise targets your hamstrings and glutes and also requires you to activate your abdominal and lower-back muscles in order to keep your body stable.
How to do it: Lie faceup on the floor with your knees bent, feet flat on the floor, and arms by your sides. Raise your hips so your body forms a straight line from your shoulders to your knees, squeezing your glutes and pressing slightly out with your knees the entire time. Hold for 10 to 30 seconds in the up position, then lower back down.