How to Do Jackknife Sit-Ups

If you’re sick of crunches and planks, we hear you.

Add variety to your exercise routine and try the jackknife sit-up — but be ready for a challenge.

Because there are many health benefits to working your core muscles — like achieving a flatter stomach — many of us can’t get enough core exercises.

Jackknife sit-ups (or V-ups) are popular right now because you only need your body and a mat to perform them. That’s right, no fancy equipment necessary!

Jackknife sit-ups are a beginner-friendly, low-impact, and can help carve out your abdominal muscles (rectus abdominis).

Plus, there are plenty of ways to modify and increase the intensity of this exercise. So, get ready to shred your six-pack.

Jackknife Sit-Ups: Step-by-Step Instructions

Follow these steps to increase your core strength. Floor or rug burns are the worst, so grab a mat to cushion your spine before you begin.

Lengthen your body on your mat. Lie flat on your back and neutralize your low back (avoid a rounded or an arched spine).
Extend your legs out long and reach your arms above your head.
Hover your arms and legs a few inches off the mat (still press your tailbone into the mat).
Take a deep breath, and on your exhale lift your head and pull your arms and legs up into a V-shape (lift roughly 30-45 degrees away from the mat).
On your lift, keep your legs straight and your arms parallel to your thighs.
Lower back down to your starting position.
Repeat these steps for 10 to 12 reps and 2 to 3 sets.

How to Make Jackknife Sit-Ups Easier

We understand that this exercise is hard. Build up to the burn with these simple variations that will still cause your muscles to quake.

Try doing single leg jackknife sit-ups, alternating lifting one leg at a time.
Work through jackknife sit-ups with bent elbows and knees, rather than straight arms and legs.

How to Make Jackknife Sit-Ups Harder

Now that you’ve worked through the basics of jackknife sit-ups, we’ve cultivated some ideas that can help you increase the challenge and add some flare.

Hold a weight (dumbbell, medicine ball, or weight plate) between your hands! Added weight will for sure help you jack-up your jackknife intensity.

Benefits of Jackknife Sit-Ups

“Jackknife sit-ups directly target the [abdominals] and strengthens the entire core,” explains Alexa Cohen, a personal trainer at Crunch Union Square in New York City.

With a stronger core, you may have more endurance for your other favorite activities.

Jackknife Exercise Alternatives

Perhaps you’ve mastered the jackknife sit-up, and you’re looking to expand your horizons. Here are jackknife sit-up exercise alternatives for you to try out.

Side jackknife sit-ups

Come onto your side and bend your bottom elbow to 90 degrees.
Press your hips into the mat and extend your legs long. Bend your top arm and place your hand behind your head.
Crunch your elbow to your hip to engage your oblique muscles. Simultaneously lift your top leg toward the ceiling.

Stability ball jackknife

From a high plank position with your hands under your shoulders, lift your hips into the air and keep your feet on a stability ball.
Contract your abdominal muscles to close the distance between your chest and the ball.
Keep your hips down and roll the ball forward on the contraction.