Smart Workout Diary

Side Jacknife

The side jackknife is a bodyweight abdominal exercise performed lying on one side while bringing the upper body and legs together. It primarily targets the obliques and also trains the rectus abdominis and hip flexors. It supports core strength, lateral trunk control, and abdominal muscular endurance.

Demonstration

Side Jacknife — demonstration 1
Side Jacknife — demonstration 2

Instructions

  1. Set up: Lie on one side with your legs straight and stacked. Extend the lower arm along the floor and place the upper hand lightly behind your head.
  2. Brace: Keep your neck long, draw your ribs toward your pelvis, and tighten your abdominal muscles before moving.
  3. Lift: Exhale as you raise both legs and your upper torso, bringing the upper elbow toward the outside of your thighs.
  4. Return: Lower your torso and legs together with control until they are just above, or gently return to, the floor. Do not drop into the bottom position.
  5. Repeat evenly: Complete the repetitions on one side, then switch sides. Stop or reduce the range if you cannot keep the movement controlled and comfortable.
Muscle Group
Obliques
Other Muscle Groups
Hip Flexors
Type
Strength
Mechanics
Isolation
Equipment
Body Only
Difficulty
Beginner

Technique tips

  1. Move as one unit: Lift the torso and legs together rather than swinging the legs independently.
  2. Protect your neck: Keep the upper hand light behind your head; do not pull the head forward with the arm.
  3. Use a controlled range: Keep the hips stacked and avoid rolling backward or forward as you lift and lower.
Exercise library