Fitness Tracker is a local-first, privacy-focused fitness application that helps you measure progress, track workouts, and stay consistent — all without subscriptions, logins, or tracking. This page covers how to perform the jackknife sit-up, including tips, variations, and the muscle groups it targets.
Instructions
- Lie down slowly flat on the floor (or exercise mat) on your back with your arms extended straight back behind your head and your legs extended also. This will be your starting position. for best results.
- As you exhale, bend at the waist while simultaneously raising your legs and arms to meet in a jackknife position. Tip: The legs should be extended and lifted at approximately a 35-45 degree angle from the floor and the arms should be extended and parallel to your legs. The upper torso should be off the floor. for best results.
- While inhaling, lower your arms and legs back to the starting position. for best results.
- Repeat this exercise for the recommended amount of repetitions. for best results.