Welcome to Trainer of the Month Club, our brand-new fitness series, where we tap the coolest, most in-the-know fitness leaders to create a month-long fitness challenge. On Mondays, we have our “sweat drops” where you’ll get access to the week’s workout that you can follow along at home. This week, Kimmy Kellum from East River Pilates is taking us through a full-body Pilates workout.

Oftentimes, I’ll joke that I wish I could crawl through my workouts. But that doesn’t really work. The next best thing (besides seated yoga or exercising while lying down)? A Pilates workout that you can do on all fours.

I’m not kidding. Our Trainer of the Month, Kimmy Kellum—fitness goddess and founder of East River Pilates—is here to prove that, to reap the perks of Pilates, you don’t even need to stand up. So you can do this week’s Pilates workout while staying on your hands and knees.

That’s not to say it’s going to be easy, though. “What I love about this workout is that it is deceivingly difficult,” says Kellum. “It looks really simple, but it’s really hard if it’s done well.” Oh, and another thing? It’ll help you out if you deal with lower back pain on the reg (read: me). All it takes is 13 moves, about nine minutes, and you’re going to feel a true burn without ever having to be on your feet. Keep scrolling to try it for yourself.

Try Kellum’s full-body Pilates workout

1. Serratus push-up: On all fours, take your hands right underneath the shoulders. Honor the natural S-bend of your spine, so try to avoid over-tucking or over-extending the low back. Find a place in-between posterior and anterior tilt, where you have a little inward curve on your back. Keep your hips right on top of your knees, starting in a sunken position. Continue to press away from the floor to set those shoulder blades into alignment, working on mobilizing the scapula. Inhale to lower, exhale to press away. Keep your weight in your hands and try to pretend like you’re squeezing a pencil between your shoulder blades as you lift.

2. Knee hover: Tuck your toes under and commence with a knee hover. Take a deep belly breath and let your ab muscles soften. As you exhale, hug your abdominals and draw your bellybutton into your spine. When you have no air left, start to hover those knees over the ground. Inhale softly as you tap them back down to the mat. Exhale to lift, drawing your abs in but without changing the alignment of your spine, and inhale to lower. Keep going with this and make sure you have a soft bend in your elbows. If you’re finding this is sensitive for your wrists, try fisting your hands. Or you can do this from down on your elbows with your palms facing up.

3. Knee hover with pulse: Keep your knees hovering and pulse for ten seconds, not allowing anything to move but your knees.

4. Knee hover with marching: With your knees still hovering, start to float one leg up at a time. Keep the raised leg bent, with your foot up in the air. Prenatal mamas, don’t lift the knees for this one. You can stay on the ground and simply float one leg up at a time. Either way, nothing else changes in your body, and your knees are as low to the floor as possible.

5. Single-arm reach: Float your knees back down with control. Untuck your toes, keeping your shoulders broad. Only move one body part. Take a deep breath, and as you exhale, hug your abdominals and extend one arm forward, inhale slowly and float it back with control. Lift the other arm. If you’re doing this correctly, it’s very challenging. Your chest is supporting your body, your glutes are kicking in to allow your body to stay still. Avoid mobilizing the spine from side to side. Keep everything really frozen as you extend each arm one at a time.

6. Single-leg reach: Now slide one leg straight back at a time. This is more challenging than the arms. The key thing to focus on is disassociating your leg from your hip joint. We don’t want to extend the low back here. Keep your abs engaged in this series. Separate or isolate the leg from your pelvis so that you keep the pelvis really still.

7. Opposite arm plus leg reach: Extend one arm and the opposite leg at a time. Your supporting elbow should not hyperextend—keep it a little bent, so all of your arm muscles are fired up. Exhale to reach, and inhale to lower. Your pelvis should stay neutral and everything else stays in place.

8. Diagonal reach—left leg: With your right arm forward, and left leg back, take a diagonal reach, floating your right arm to the right and your left leg out to the left. This is where you start to fire up through the obliques and gluteus medius. Exhale to open, inhale to bring your limbs back to center, leaving everything extended.

9. Diagonal reach—right leg: Check your alignment, making sure everything is active and you’re pushing down through your hands. Extend the opposite hand and leg. Exhale to open out to a diagonal, and inhale to bring everything back to center. You might get shaky as your balance on one side may not be as controllable as on the other. Take a child’s pose when you’re done with this one to reset your hips and open up through the chest.

10. Donkey kick—right: Get down onto your forearms. You can clasp your hands together, but try to keep your palms facing up and the forearms as wide as your chest, parallel to one another. Start with donkey kicks as you bend your right knee and try to kick your butt with your heel. On your exhale, lift that leg as high as you can, then inhale to lower with control. You’re disassociating your leg from your hip, so try not to make this about your back.

11. Knee cross—right: Cross your right knee over to the opposite knee while keeping it lifted.

12. Donkey kick—left: Bend your left knee and kick your heel to your butt. Inhale to lift, exhale to lower. The back of your neck should stay really long. If you’re not feeling it in your obliques, take a little weight over to the left.

13. Knee cross—left: With your left knee still bent, take it to the opposite knee and lift up to find parallel. Keep pushing down through the forearms.

Want more of this to do? Here’s Kellum’s exercise from last week, which is a Pilates glutes workout. And here’s a Megaformer workout you can do at home, which is even harder.