Jack Knife Sit-up
Description
The jack knife sit-up (also called the V-up) is a core exercise where you lie on your back and simultaneously lift your torso and legs to meet in a V-shape, with your hands reaching toward your toes. It trains both the upper and lower abs in one movement and is a more advanced version of the standard sit-up.
Equipment Required
Jack Knife Sit-up Instructions
- Lie flat on your back with arms extended overhead and legs straight.
- Brace your core. Press your lower back into the floor.
- Simultaneously lift your torso and your straight legs upward, reaching your hands toward your feet.
- Meet at the top in a V-shape with your fingers reaching toward your toes.
- Squeeze your abs hard at the top.
- Lower under control back to the start with arms overhead and legs extended.
- Stop just before your hands and heels touch the floor to maintain tension.
- Repeat for the desired number of reps. Use bent knees if too difficult.
Jack Knife Sit-up Form & Visual
Jack Knife Sit-up Benefits
- Trains upper and lower abs simultaneously
- Builds core strength and endurance
- No equipment needed
- Time-efficient core exercise
- Excellent finisher for ab workouts
- Develops body control
Jack Knife Sit-up Muscles Worked
- Rectus abdominis (upper and lower)
- Hip flexors
- Obliques (secondary)
- Quadriceps (keeping legs straight)
Jack Knife Sit-up Variations & Alternatives
- Tuck Crunch (bent knees)
- Crunch with Leg Lift
- Ab Mat Sit-Up
- Sprinter Crunch
- Tuck V-Up (knees bent)
- Weighted Jack Knife Sit-Up
