If you’ve noticed your running form feeling weaker than usual and your times slowing down, consider upping the amount of core work you’re doing each week.

“Runners all need a strong core—everything that isn’t arms and legs—to primarily help with stabilising the torso when running,” Yusuf Jeffers, a certified personal trainer and running coach, tells Runner’s World. “When the core isn’t properly engaged, form deteriorates, slowing the runners down and exposing them to potential injury.”

That’s why he created this 20-minute ab workout. While there are lots of different core exercises one can do to help improve stability, posture, and speed, when done in a timespan of 20 minutes, it also has the added benefit of training muscular endurance for the core, according to Jeffers.

How to do it: This circuit is performed by adding an exercise to consecutive rounds of 30 seconds of work. For example:

• Exercise #1, perform for 30 seconds
• Rest 30 seconds
• Exercise #1, perform for 30 seconds
• Exercise #2, perform for 30 seconds
• Rest 30 seconds
• Exercise #1, perform for 30 seconds
• Exercise #2, perform for 30 seconds
• Exercise #3, perform for 30 seconds
• Rest 30 seconds

Five exercises done in 30-second intervals will add up to 10 minutes of work, so the circuit should be repeated twice to add up to 20 minutes of work. You will need a set of dumbbells and sliders (or a towel) to complete the workout. An exercise mat is optional, but recommended.

Half-Kneeling Reverse Chop With Dumbbell

Start in a half-kneeling position with knees bent at 90-degree angles, right foot in front, holding a dumbbell with both hands at your left side. Keeping arms straight, swing the dumbbell up and across your body above left shoulder with control. Reverse the motion to return dumbbell back to starting position. Repeat. Then switch sides.

Sprinter Sit-Up With Dumbbells

Start lying face-up, arms at your sides holding a dumbbell in each hand, and legs extended. Quickly sit up, bringing your left knee toward your chest while swinging your right arm forward, bending the elbow (as if running). Return to starting position. Repeat on the other side and continue alternating.

Half Hollow Hold With Dumbbell

Lie face-up with knees bent and held over hips, feet flexed and off floor. Place arms down at sides, holding a dumbbell in right hand. Lift shoulders off floor and lift right arm straight up toward ceiling, then back so your right bicep is in line with your right ear. Lift left arm so it’s hovering a few inches above the ground. Extend left leg straight out. Hold this position for the allotted amount of time, then switch sides.

Supine March

Lie face-up with knees bent and held over hips, feet flexed and off floor. Place hands behind head and lift shoulders off floor. Tap right heel on ground, then return to starting position. Tap left heel on ground, then return to starting position. Continue alternating.

Pike With Leg Raise

Start in high plank position with both feet on a towel (toes should be curled under, the balls of the feet on the towel). Engage your core and lift hips straight up as your feet come forward toward your hands—your body should form an inverted V position. At the top, lift left leg toward the ceiling. Hold it up as you slide feet backward, returning to high plank position. Then step left foot back down. Repeat, this time lifting right leg. Continue alternating.

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