The hip abduction and adduction machines feel incredible: You can use a lot of weight, so you feel strong, and both exercises leave you with a serious burn. But they're dangerous, says Nick Tumminello, owner of Performance University in Baltimore, because your body isn't designed for those movements.
"There's nothing remotely like these movements in life," he says. The muscles the machines work "are primarily stabilizers for when you're standing or moving around. When you do a stepup or lunge, you're working them, plus all the other stuff."
What to do instead: Get out of the chair and work abduction and adduction while standing, suggests Aaron Brooks, a biomechanics expert and owner of Perfect Postures in Auburndale, Mass. Affix a band or the handle of a cable machine around your right ankle while you stand with the machine (or fixed point of the band) on your left. Keeping an erect posture, lift your weighted leg out and away from your body to 3 o'clock. To perform the adduction (pulling in)maneuver, stand with your weighted leg next to the machine, crossing it in front of your planted leg to 9 o'clock.
Why it's better: "With the cable hooked to your right leg, balancing on your left leg, you're engaging your core, working the adduction or abduction, and the leg you're stabilizing—you're getting a tremendous amount of strength in that leg," Brooks says.