In 2007, researchers at the Madonna Rehabilitation Hospital in Lincoln, Nebraska, set out to learn which machines kick your ass the hardest. Here’s how their findings shake out, as well as a few glute-blasting pointers from Lindsay Dunlap, a personal trainer at the Sports Club LA in New York City.

TREADMILL

a) Jogging

Make sure your heels, not the balls of your feet hit the ground first.

b) Walking

On a treadmill, increase the incline. On the road, try walking sideways. This will work your bum from a different angle as you pull your leg away from your body.

ELLIPTICAL

Ease your hips back so your butt sticks out a bit and push down with your heel as much as possible.

BIKING

Ditch the recumbent ride for an upright one. Then sit a little farther back on the seat and focus on pushing the pedals down forcefully. If you’re spinning, stand up and stick your butt out while leaning forward.

STAIR STEPPING

Lean forward slightly at the waist and take larger steps, as though you’re climbing two at a time. Let go of the rails forcing your glutes to take the brunt of the stabilization duties.

The percentage of glute muscles activated in this table mostly refers to gluteus maximus, the largest of the three glute muscles.