Jackknife Sit-Up

Setup

1. 01Lie flat on your back on a mat.
2. 02Extend the arms straight overhead along the floor.
3. 03Straighten the legs with toes pointed and heels together.
4. 04Press the lower back gently down and brace lightly.

Execution

1. 01Exhale and lift the arms, shoulders, and legs off the floor at the same time.
2. 02Fold at the hips so the hands and feet rise toward each other.
3. 03Touch or approach the shins or ankles at the top of the V.
4. 04Lower arms and legs together under control without letting them rest fully.

Checkpoints

• -Arms and legs move simultaneously, not one after the other.
• -The legs stay straight; knees do not bend to meet the hands.
• -The lower back returns to the mat before the next rep begins.
• -Balance stays centered on the tailbone at the top.

Common mistakes

• -Throwing the arms to whip the torso up.
• -Bending the knees so the touch happens without ab work.
• -Arching the lower back hard as the limbs lower.
• -Rushing reps and rolling around on the spine.