Why should you skip this popular gym machine? "Think about it, our leg muscles are designed to move our body during walking—sitting in a chair and moving the legs in and out does not work the muscles the way they are designed to move our skeletal structure and is a complete waste of precious training time," says Pete McCall, an exercise physiologist for the American Council On Exercise. Instead, train the muscles of the inner thigh, hamstrings, and glutes with single-leg Romanian deadlifts, McCall suggests. To do single-leg Romanian deadlifts (pictured), stand with feet together and knees slightly bent, holding a dumbbell with left hand. Engage abs, and balancing on right leg, hinge forward at hips, lifting left leg behind hip until chest is almost parallel to the floor. Keep spine naturally straight, abs engaged, and return to start.