The exercise of many monikers, this move is challenging no matter what you call it. 

The V-sit–also known as the Jackknife, V-up, and Pike Crunch–is a supine abdominal maneuver that isolates your core. Mainly targeting your abdominals and obliques while also tackling your quads and hams, this bodyweight resistance exercise can be incredibly effective in building strength and physique. 

Performed by creating a V-shaped hip-hinge movement, form is more important than reps or sets. If proper form cannot be maintained throughout this movement than you should stop reps immediately as it can put your back, neck and shoulders at serious risk. 


No documented records exist for the origin of the sit-up, the crunch, or any other supine ab work. What we do know is that humans have been performing sit-ups since before the 19th century and that other moves such as the classic crunch came later as modifications of the original. 

Supine ab work’s demise, on the other hand, is very well documented.

One of the most respected back pain specialists on the planet, Dr. Stuart McGill, effectively shut down the US Military’s use of the sit-up in basic fitness testing. Working with the United States National Institute for Occupational Safety and Health, he conducted experiments on the effects of sit-ups and crunches on the spine. 

He concluded they were unsafe to perform, issuing the following statement to the Toronto Star in 2016: “We measured the loads on the spine with each sit-up. [The spinal loads] were right on the limit noted by us as causing damage over time and with repetition.” 

McGill drove this point home, by adding “If [your goal] is to become faster, stronger, or if it’s to become injury resilient and have less pain in life and make yourself generally fit to enjoy life, then the answer is don’t do sit-ups.

As a result, the U.S. Armed Forces no longer uses or recommends sit-ups or crunches for training. 

How to Perform a V-Sit

Step 1: Lying face-up on a mat or smooth surface, engage your abs as you pull your shoulder blades back and extend your arms out above your head and your legs out straight. Press your lower back into the mat and maintain contact throughout the entire movement. 

Step 2: Synchronize the movements of your arms and legs to form a “V.” Exhale as you raise your upper torso off the mat in a slow and controlled motion.

Step 3: Inhaling, maintain control as you slowly lower your torso, arms, and legs back down to the mat. Focus on your breathing and synchronizing your movements with your breathing.

Step 4: Repeat this process until you have achieved your desired number of reps or until you can no longer maintain proper form throughout the movement. 


  • Flattens the midsection
  • Improves coordination
  • Strengthens the core
  • Improves athletic performance
  • Increases functional fitness
  • Increases oblique strength
  • Boosts metabolism
  • Improves balance and posture


After you have mastered the basic V-up, here are some added challenges for you to try:

  • Contact V-sit
  • Hovering V-sit
  • Weighted V-sit

Exercise Your Abs with Caution 

Dr. Stuart McGill, after killing the sit-up and classic crunch with his research, did give the fitness world a few safe alternatives for targeting the core. He recommended planks as being not only safe, but more effective at activating the core. He even developed his own crunch modification as a better alternative.

The McGill Crunch, or McGill Curl-Up, prevents the lumbar vertebrae from activating during the movement by leaving one leg flat on the floor and keeping both hands under the lower back during the crunching movement. This serves to reduce stress on the lower back. 

Consult your physician before beginning any controversial exercise regimen and make sure you are fit enough to attempt it.

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