Risky Exercise

No. 3: Upright Row

The problem: Pulling weights, a barbell, or a weighted cabled bar up under your chin can compress the nerves in the shoulder area, impinging the shoulder.

No. 4: Leg Press with Cramped Knees

From a reclining position, you push the plate up and bring it down in this common exercise to work the quadriceps, hamstrings, and glutes. The problem comes when you bend your legs too far -- past a 90-degree angle -- which can hurt your back and knees.