Developing a muscular imbalance isn't the worst thing that can happen from ignorant training. (Blowing your intestines out your butt during a squat, for instance, would be much worse.) But over-developing one muscle group while neglecting another does result in problems. For example, guys who have severe discrepancies between quad strength and glute strength are more prone to injury and are limited in how much they can lift. Use this test from Cameron McGarr, C.S.C.S., a trainer in Santa Clarita, Calif., to check and balance your lower body.

Stand three feet in front of a bench that's about knee height. Rest the top of your left foot behind you on the bench [1]. Keeping your torso upright, take five seconds to lower your body until your left knee nearly touches the floor [2]. Now take another five seconds to straighten your right leg, standing back up. That's one rep. Do five reps, then switch legs and repeat.

If your right knee turned inward at any point (moving toward your big toe), it means your glutes are weak. Strengthen them by doing more hip-extension exercises,such as dead lifts, single-leg hip extensions, and step ups. If at any point your knee moves toward the outside of your foot, your quads are the weak link. You need to do exercises that stress them more directly, such as front squats and split squats. If one leg is more imbalanced than the other, use primarily single-leg exercises for either your hips or quads to bring it in line with the other leg.