10 Best Side Jackknife Alternatives for Core Strength

The 10 Best Side Jackknife Alternatives

10 substitutes, ranked by how closely each one matches the Side Jackknife on movement pattern, muscles worked, equipment and body position. The higher the score, the less you change. Cards with a "How to perform it" link open to show the steps; every card title links to that exercise's own alternatives page. Harder versions are tagged as progressions and kept out of the top spot even when they score higher.

1. Play demonstration

   1. Exercise Ball One Leg Prone Lower Body Rotation

   79% match

   Glutes · Intermediate · Compound

   A looser match: it works the glutes rather than the abdominals.

   • Stability-ball

   How to perform it

   1. Lie face down on the stability ball with your hips resting on the ball and your legs extended straight behind you.
   2. Place your hands on the ground in front of you for support.
   3. Engage your glutes and core muscles to stabilize your body.
   4. Slowly lift one leg off the ground, keeping it straight and parallel to the floor.
   5. Rotate your leg outward, away from your body, while keeping your hips and upper body stable.
   6. Pause for a moment at the end of the rotation, then slowly return your leg to the starting position.
   7. Repeat the rotation with the other leg.
   8. Continue alternating legs for the desired number of repetitions.

   Sets and reps: 3 or 4 sets of 6 to 10 reps on each side.

   Why this matches

   • Primary muscle: glutes, not abdominals
   • Equipment: bodyweight only, the same as the Side Jackknife
   • Body position: lying face down, the same as the Side Jackknife
2. Play demonstration

   2. Prone Twist On Stability Ball

   76% match

   Abs · Intermediate · Isolation

   A looser match: it works the abs rather than the abdominals.

   • Stability-ball

   How to perform it

   1. Start by lying face down on a stability ball with your feet shoulder-width apart and your toes touching the ground.
   2. Place your hands behind your head or cross them over your chest.
   3. Engage your core muscles and slowly lift your upper body off the ball, keeping your back straight.
   4. Rotate your torso to one side, bringing your shoulder towards your hip. Keep your hips and legs stable throughout the movement.
   5. Pause for a moment, then return to the starting position.
   6. Repeat the rotation to the other side.
   7. Continue alternating sides for the desired number of repetitions.

   Sets and reps: 3 sets of 10 to 15 reps.

   Why this matches

   • Primary muscle: abs, not abdominals
   • Equipment: bodyweight only, the same as the Side Jackknife
   • Body position: lying face down, the same as the Side Jackknife
3. 

   3. Decline Oblique Crunch

   74% match

   Abdominals · Intermediate · Isolation

   Pick this when you want an easier version that still works the abdominals.

   • Bodyweight

   How to perform it

   1. Secure your legs at the end of the decline bench and slowly lay down on the bench.
   2. Raise your upper body off the bench until your torso is about 35-45 degrees if measured from the floor.
   3. Put one hand beside your head and the other on your thigh. This will be your starting position.
   4. Raise your upper body slowly from the starting position while turning your torso to the left. Continue crunching up as you exhale until your right elbow touches your left knee. Hold this contracted position for a second. Tip: Focus on keeping your abs tight and keeping the movement slow and controlled.
   5. Lower your body back down slowly to the starting position as you inhale.
   6. After completing one set on the right for the recommended amount of repetitions, switch to your left side. Tip: Focus on really twisting your torso and feeling the contraction when you are in the up position.

   Sets and reps: 3 sets of 8 to 12 reps, and add reps before you add load.

   Why this matches

   • Primary muscle: abdominals, the same as the Side Jackknife
   • Equipment: bodyweight only, the same as the Side Jackknife
   • Body position: lying on your back, not lying face down
   • Balance: easier to stay steady on than the Side Jackknife
4. Play demonstration

   4. Exercise Ball Back Extension With Rotation

   72% match

   Spine · Advanced · Compound

   A looser match: it works the spinal erectors rather than the abdominals.

   • Stability-ball

   How to perform it

   1. Start by lying face down on the stability ball with your hips resting on the ball and your feet firmly planted on the ground.
   2. Place your hands behind your head or cross them over your chest.
   3. Engage your core and slowly lift your upper body off the ball, extending your back until your body forms a straight line from your head to your heels.
   4. Pause for a moment at the top, then slowly rotate your torso to one side, keeping your hips and legs stable.
   5. Return to the center and repeat the rotation to the other side.
   6. Lower your upper body back down to the starting position and repeat for the desired number of repetitions.

   Sets and reps: 3 or 4 sets of 6 to 10 reps on each side.

   Why this matches

   • Primary muscle: spine, not abdominals
   • Equipment: bodyweight only, the same as the Side Jackknife
   • Body position: lying face down, the same as the Side Jackknife

5. 5. Roller Body Saw

   72% match

   Abs · Intermediate · Isolation

6. Play demonstration

   6. 45° Side Bend

   67% match

   Abs · Beginner · Isolation

   A looser match: it uses the same equipment, but it works the abs rather than the abdominals.

   • Bodyweight

   How to perform it

   1. Stand with your feet shoulder-width apart and your arms extended straight down by your sides.
   2. Keeping your back straight and your core engaged, slowly bend your torso to one side, lowering your hand towards your knee.
   3. Pause for a moment at the bottom, then slowly return to the starting position.
   4. Repeat on the other side.
   5. Continue alternating sides for the desired number of repetitions.

   Sets and reps: 3 sets of 8 to 12 reps on each side, and add reps before you add load.

   Why this matches

   • Primary muscle: abs, not abdominals
   • Equipment: bodyweight only, the same as the Side Jackknife
   • Body position: standing, not lying face down
   • Balance: easier to stay steady on than the Side Jackknife

7. 7. Oblique Crunch

   67% match

   Abs · Intermediate · Isolation

8. 8. Seated Side Crunch (Wall)

   67% match

   Abs · Beginner · Isolation

9. Progression

   9. Russian Twist

   67% match

   Abs · Intermediate · Isolation

10. 10. Bottoms-up

    67% match

    Abs · Intermediate · Isolation