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 Pilates workout focused on your core and glutes.

As I browse fitness classes to take, these days, those that target “abs and ass” seem to be in excess. There’s just something so satisfying about working your glutes and core in one workout. So I’m thrilled to present this week’s Trainer of the Month Club workout from East River Pilates founder Kimmy Kellum—a Pilates sesh that’s going to work your booty and core all in one go.

“This is an obliques and outer thighs workout, or, in other words: abs and ass,” says Kellum in this week’s video. All you’re going to need is a mini stability ball, or you can grab a blanket and roll it up. These props are simply to increase your range of motion for more of a challenge, since you’re balancing your torso on top of it the entire time (we’re working on balance, too!).

In the course of nine minutes, you’re going to feel your obliques, your bum, your outer thighs, and your abdominal muscles burn—trust me. Let’s get to it, shall we?

The Pilates core workout to try at home now

Start with all of these exercises on the left side, and once you’ve completed them, for round two, switch to your right side and repeat them from beginning to end.

1. Oblique curl: Start by positioning your body in the right place. Make sure the ball is in the center of your torso, and lie down. If you have a slightly longer torso, move it higher up, if your torso is shorter, move it lower down on your body. The bottom leg is at 90 degrees at the knee and hip, and the top leg is extended long with your spine. Lie onto the ball to test your balance—this is the hardest part. While keeping the legs anchored down, with the bottom arm tucked in and top arm open, take a deep breath in. As you exhale, draw your bellybutton back into your spine. Your pelvic floor is lifting as you press into the ball and lift your chest. Your legs don’t change position. Your bottom arm opens and closes as you lower down.

2. Oblique curl with leg lift: Hold your torso up, and as you lift the leg, try not to move your pelvis. Keep the top hip stacked on the bottom hip. Exhale, pressing down into the bottom knee and inhale to fold in and lower. When your torso is up, your leg is lifted—then you lower it all down. Hold it up there for some pulses. Your hand can be on your hip for a modification, or you can keep your hands behind your head if you’re advanced. Add a leg lift if you want, too. Then, stretch it all out.

3. Oblique twist with knee pull: Meet back up into a lift. Extend your bottom leg so you have more pressure and more of a base. Bend the top knee and twist towards that leg, and inhale to come back to center. Squeeze your gluteus medius muscle to pull that knee in. Use a slight extension of the hip joint as you reach your leg slightly behind your body. Exhale twist, inhale to center.

4. Leg lift: Hold your hand on your hip and just lift the upper leg, then lower all the way to the floor. A modification is that you can let your head be down and your elbow lower to the floor, but keep your lats engaged so you’re lifting slightly off of the ball. Don’t let your head be out of alignment of your spine. For an extra challenge, you can lift your torso. Keep breathing as naturally as possible.

5. Leg circle: Point your toes and take little circles with that upper leg. Keep them tiny, or you can go bigger—the bigger the circles, the harder they are. Then reverse the direction. When you’re done, stretch out your body.

For more workouts like this, try Kellum’s full-body Pilates workout, or her Pilates glutes workout that is all about that peach.