The jackknife situp is a bodyweight exercise targeting the abdominal muscles. It involves simultaneously lifting the legs and upper body to meet in the middle, engaging the core and hip flexors.
Also Works
Hip Flexors
How to Perform
1
Lie flat on your back with your legs extended and your arms overhead.
2
Engage your core and lift your legs and upper body simultaneously, reaching your hands towards your toes.
3
Pause for a moment at the top, then slowly lower your legs and upper body back down to the starting position.
4
Repeat for the desired number of repetitions.
Pro Tips
•Reach your hands toward your toes at the top while simultaneously lifting your legs, forming a V shape with your body.
•Keep your legs as straight as possible throughout the movement for maximum ab engagement.
•Lower both your arms and legs simultaneously and under control. Don't let them crash down to the floor.
Common Mistakes
•Bending the knees significantly, which shortens the lever arm and reduces abdominal demand.
•Using momentum by swinging the arms to generate force rather than initiating the movement with the abs.
•Not reaching the full V position at the top, essentially doing a half-rep.