This is how you perform the Jack Knife exercise
Traing Details Jack Knife
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Primary MuscleStraight Abs
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Secondary MuscleInner Abs, Obliques
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EquipmentBody weight
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LevelAverage
Guide for Jack Knife
- This is a though exercise
- You can do it in two different version. The harder one with straight legs and the easier one we bended knees
- Bent knees: Lay down with your back on the floor. Extend and straighten your arms over your head. At the same time as you move your arms and torso forward you lift your knees up against your body. When your arms meet your knees your slowly reverse the movement. Your lower back should be pressed against the floor all the time during the exercise
- Straight legs: Lay down with your back on the floor. Extend and straighten your arms over your head. At the same time as you move your arms and torso forward you lift your straight legs up against the roof over your pelvis. When your arms meet your legs or toes your slowly reverse the movement. Your lower back should be pressed against the floor all the time during the exercise
- Important to suck in your belly and press the lower back against the floor at the start of the exercise
- Do not let your feet touch the floor, you will then loose contact with your abs