The Bulgarian split squat is one of the toughest lower-body exercises. It can also be one of the more difficult abs exercises you’ll ever do, too. Just pick up a dumbbell and follow the routine shown in the video above.

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The dumbbell level will change every 5 reps. You’ll start with the most challenging level (overhead) and work your way down to the least challenging level (hip).

It’s essentially a stability strip set, but you don’t have to change out the load. So right when the exercise starts to get super tough, you’ll decrease the level difficulty level and continue to crank out more reps. And increasing the number of reps you do under fatigue can spur muscle growth.

When you hold the dumbbell in the same hand as your lead leg, you’ll work your quads more. When you hold the weight in the opposite hand of your lead leg, you’ll work your glutes more.

Related: The 5-Minute Workout That’s So Tough We Call It a ‘Death Set’

And since you’re asymmetrically loading your body with only one dumbbell, you’ll work each side of your core independently. Your abs will feel as if they’re on fire!

How to Do the Bulgarian Split Squat Burner

Do 5 reps at each level. Don’t rest between level changes.

ROUND 1
1. Overhead level: right arm and right leg
2. Shoulder level: right arm and right leg
3. Hip level: right arm and right leg
4. Overhead level: left arm and right leg
5. Shoulder level: left arm and right leg
6. Hip level: left arm and right leg

Rest 30 to 60 seconds between rounds.

ROUND 2
1. Overhead level: left arm and left leg
2. Shoulder level: left arm and left leg
3. Hip level: left arm and left leg
4. Overhead level: right arm and left leg
5. Shoulder level: right arm and left leg
6. Hip level: right arm and left leg

Repeat this process 2 to 3 more times.