Jack knive

Main body focus: abs.

jack knive

Jack knive

Why do this?

Jack knives is an advanced version of the leg raises and help you to strengthen your (lower) abdominal muscles. It’s an effective exercise to help you gain a stronger core that is necessary for most sports varying from endurance to explosive motions.

How to do this?

  1. Lie on a flat bench or ground with your arms stretched out alongside your head.
  2. Your legs should be unsupported by the bench or ground from below your knees.
  3. With your feet together and your toes flexed upwards, raise your straight legs up a few cm off the bench; both of your legs should have no contact with the bench. This is your starting position.
  4. Keep your legs straight with a slight bend in the knees and raise your legs to just before 90 degrees.
  5. Simultaneously raise your upper body and touch your ankles with your hands while keeping your arms stretched at all times.
  6. Pause at the top and lower your legs in slow controlled manner back to the starting position.
  7. Repeat.

How to vary?

Increase difficulty: Increase the speed with which you do the exercise. All force and momentum should be mostly regulated with your abs.

Decrease difficulty: Bend your knees to shorten the distance you need to cross to touch your ankles. This lowers the total amount of stress experienced in your abs.

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