Only Have 15 Minutes? This HIIT Ab Workout Makes the Most of Every Rep

“Focusing on time over reps is a great way to prioritize the quality of your work to improve your form and learn new skills in a safe environment,” says Ben Lauder-Dykes, CPT, trainer and Fhitting Room instructor and the host of our June Movement of the Month Club, focusing on a 4-week ab challenge.

"And proper form is always a priority, especially when it comes to ab exercises, because it's important to make sure that we're challenging and training the target muscles without other muscle groups taking over."

Join the movement

If you’re following along with our June 2024 Movement of the Month Club, these are the moves for week 1. You’ll do one ab exercise each day, Monday through Saturday. (But you can do this workout any time!)

Then on Sunday, you’ll do the full 15-minute workout. You’ll do 30 seconds of each exercise, followed by 15 seconds of rest, repeating each exercise 3 times before moving on to the next exercise.

Here's your 15-minute HIIT ab workout

1. Straight-leg sit-up

This sit-up variation builds strength and power in your core, while increasing your overall abdominal muscle endurance and enhancing flexibility in the hips and lower back.

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If this version doesn't challenge you enough, increase the difficulty by straightening both legs or holding a weight across your chest or above your head.

1. Lie on your back with one leg extended straight out and the other knee bent and pointing up to the ceiling.
2. Raise your arms over your head or hold them behind your head for more intensity.
3. Lift your upper body off the floor to a sitting position, keeping your legs anchored to the ground.
4. Slowly lower yourself back down to the starting position.
5. Repeat, then switch sides to do the same number of reps.

2. Forearm plank

This foundational ab exercise challenges your core stability and strength, which translates to better balance throughout everyday activities.

1. Lie face down on the floor with legs extended.
2. Place your forearms on the floor, elbows below your shoulders, and hands flat on the floor.
3. Push off the floor, raising up onto your toes and resting on your forearms.
4. Keep your body in a straight line from shoulders to ankles, engaging your core and glutes.
5. Hold this position, maintaining a tight core and controlled breathing.
6. Lower your body back to the floor.

3. Dead bug

Even though it takes a bit of coordination to master this move, the dead bug exercise improves core stability, hip mobility, and athletic performance.

1. Lie on your back with your arms extended toward the ceiling and knees bent at 90 degrees and also pointing to the ceiling.
2. Engage your core to press your lower back into the floor.
3. Slowly extend your right leg and lower it toward the floor while simultaneously lowering your left arm overhead.
4. Return to the starting position and repeat with the opposite arm and leg.
5. Continue alternating sides, keeping your movements slow and controlled.

4. Figure 4 leg lift

The figure 4 leg lift effectively strengthens deep core muscles, specifically targeting the hard-to-target lower abs, Lauder-Dykes says.

1. Sit with one leg extended straight out and the other ankle crossed over the opposite thigh, forming a “figure 4.”
2. Lie down with your back along the floor and place your arms by your sides, angled out slightly for stability.
3. Press into the floor with your arms as you lift your straight leg up and perpendicular to the floor.
4. Lower your leg back down slowly and with control, hovering a few inches above the floor without arching your back.
5. Repeat for the desired number of reps before switching legs.

5. Side plank

This plank variation builds core stability, specifically in your obliques (sides of your torso), while improving upper body mobility and facilitating side-to-side movement.

1. Start by lying on your side with your legs extended and feet stacked.
2. Prop yourself up on your forearm, ensuring it's directly below your shoulder.
3. Lift your hips off the ground, forming a straight line from your head to your feet.
4. Hold this position, keeping your core and glutes engaged.
5. Hold for the desired duration, then gently lower your hips to the ground.
6. Switch sides and repeat.

6. Tuck up

Tuck ups improve core strength and dynamic power, Lauder-Dykes says.

1. Sit on the floor with your knees bent and feet flat on the ground.
2. Lean back slightly and lift your feet off the floor, balancing on your sit bones.
3. Extend your legs and arms straight out in front of you, then quickly tuck your knees to your chest while wrapping your arms around them.
4. Extend back out without letting your feet touch the floor.
5. Repeat the tuck and extend movements for the desired number of reps.