This 7-minute, core-strengthening workout tops boring old crunches any day

Ab exercises are like friendships: Quality is a whole lot more important than quantity. Which means that even if you only have seven minutes to spare in the midst of a jam-packed day, you can get an effective workout. That is, as long as you’re doing the right moves.

Thankfully for us and our core muscles, Charlee Atkins has us covered. All month long, she’s been sharing a series of core-quaking, at-home ab workouts in honor of our inaugural month of Trainer of the Month Club. Even though the moves this week require nothing more than your own bodyweight and a towel—which doubles as a piece of equipment and something you can use to help mop your sweat—the final installment might just be the most challenging one yet.

Read on for Atkins’ fourth and final core series, and check back in May for the start of a new regimen with a totally new trainer.

Complete each exercise for 30 seconds, 2 times through with no rest, for 7-minutes total.

Reverse Curl

1. 1.
   Laying on the ground with your knees and hips at a 90-degrees angle, place your hands by your hips with the palms of your hands on the ground.
2. 2.
   Slowly curl your knees into the chest, lifting your hips slightly off of the ground.
3. 3.
   Control your hips, moving slowly back down to mat.
4. 4.
   Repeat the entire move for 30 seconds.

Penguin Crunch

1. 1.
   Lie supine on your back with your hands by your hips.
2. 2.
   Lift your shoulder blades up off the mat, keeping your chest open.
3. 3.
   Moving side-to-side, reach for the insides of the ankles with your hands.
4. 4.
   Alternate sides, and repeat for 30 seconds.

Corkscrew Crunch

1. 1.
   Similar to the reverse curl, this time as you pull hips off the ground, rotate your hips like you’re corkscrewing your legs into the air.
2. 2.
   Alternate sides with your hips coming back to the mat each time.
3. 3.
   Repeat for 30 seconds.

Side Plank Hip Dips

1. 1.
   Hold a static side plank, keeping your head in line with your heels and your elbows right below your shoulders
2. 2.
   Lower the hips down a few inches towards the mat, then pull your hips back up.
3. 3.
   Repeat for 30 seconds.

Half Kneeling Towel Chop (Right Side)

1. 1.
   Start in a kneeling position with your right knee down.
2. 2.
   Keep your knees at a 90-degree angle with your back toes tucked under.
3. 3.
   Holding both sides of the towel, keep it pulled taught and pull it across the body on a diagonal.
4. 4.
   Pull up to bring the towel up, then pull the towel down to bring the towel down.
5. 5.
   Repeat for 30 seconds.

Half Kneeling Towel Chop (Left Side)

1. 1.
   Start in a kneeling position with your left knee down.
2. 2.
   Keep your knees at a 90-degree angle with your back toes tucked under.
3. 3.
   Holding both sides of the towel, keep it pulled taught and pull it across the body on a diagonal.
4. 4.
   Pull up to bring the towel up, then pull the towel down to bring the towel down.
5. 5.
   Repeat for 30 seconds.

Sit-Up + Towel

1. 1.
   Start on your back with your knees bent.
2. 2.
   Holding the towel above your chest, pull both sides of the towel as you lift up your upper body.
3. 3.
   Hold the towel at a 60-degree angle as you lift.
4. 4.
   Pause at the top and slowly lower down.
5. 5.
   Repeat for 30 seconds.

For more moves by Charlee Atkins, check out the first, second and third iterations of her April ab series, and prepare for a stronger core in no time.