If the Terminator movies have taught us anything, it’s that machines can’t be trusted. This is especially true when discussing the exercise machines in your gym, which aren’t designed to accommodate individual differences in body types, such as limb length and joint structure. As a result, training with machines, unlike with free weights, can fail to stimulate your muscles optimally and put you at risk for injury. The following are three of the worst offenders, per John Rusin, D.P.T., a physical therapist and strength coach to pro athletes (drjohnrusin.com), and our picks for more effective alternatives.
THE PROBLEM: The free-weight bench version of the preacher curl has its drawbacks, but the machine version is “orthopedically evil,” says Rusin, because you can’t reposition your body to use it safely. It forces your shoulders into a protracted position, “and in some cases even internally rotates and elevates them, putting unwanted stress on the shoulder complex.” It can also lead to an extreme stretch on the lower part of the biceps, where it inserts into the elbow, which can result in a biceps tear.
THE UPGRADE: The prone incline dumbbell curl. Set a bench to 45 degrees and lie on it chest down with a dumbbell in each hand; curl with palms facing up, bringing your elbows forward slightly as the weights rise.
“This movement allows the shoulders to remain in a neutral position,” Rusin says, “while also taking advantage of the more natural movement paths that dumbbells offer.”
Seated Ab Rotation
THE PROBLEM: This is the Chubby Checker–inspired ab machine you sit in to do a twistlike dance move. “Combining flexion, rotation, and side bending simultaneously at the lumbar spine is a terrible triad,” says Rusin. Not only do the position and added weight put your back at risk, but the element of increasing speed (the machine allows you to swing your legs violently side to side) and sudden direction changes prompt Rusin to call the ab rotation “the most debilitating machine in the gym.”
THE UPGRADE: The Pallof press. Attach a band to a sturdy object at chest height and grasp it with both hands. Stand perpendicular to the machine and press the band out to arms’ length in front of you. Don’t let it twist your body. Resisting rotation, rather than training it directly, integrates the shoulders and hips to strengthen the core.
Seated Leg Curl
THE PROBLEM: Sitting down tilts your pelvis backward, which flattens out the arch in your lumbar spine. An unnatural position to work the hamstrings in, it actually increases the compressive forces on the hams where they insert into the back of the knees. “The heavier you go, the more likely the compensation at the pelvis,” says Rusin—and that could cause a knee injury.
THE UPGRADE: The Swiss ball leg curl. It’s one of the few hamstring exercises that train the muscles’ two functions simultaneously—extending the hips and bending the knees. Lie on your back on the floor and extend your legs so that your heels rest on a Swiss ball. Brace your abs and drive through your heels to bridge your hips up. Now bend your knees and roll the ball in toward your butt. Extend your knees again and begin your next rep.