Half Jackknife
Strengthen your core! The Half Jackknife targets your abs and improves stability. A challenging exercise for a stronger you.
The Half Jackknife mainly works the core. No equipment needed: it uses just your bodyweight.
Optional Equipment
Half Jackknife Muscles Worked
Primary
Abdominals (rectus abdominis); Obliques
Secondary
Hip Flexor (iliopsoas)
Half Jackknife Variations and Alternatives
How to do the Half Jackknife
Start by lying flat on your back on the floor or a mat with your arms extended above your head and legs stretched out straight.
Engage your core and lift your shoulder blades off the floor, reaching your arms towards your toes.
At the same time, raise one leg off the floor, bringing it as high as possible without bending your knee.
Try to bring your upper body and raised leg closer towards each other, aiming to touch your toes with your hands. Your torso and leg should form a "V" shape at the top of the movement.
With control, slowly lower your upper body and leg back down to the starting position.
Alternate legs for each repetition, ensuring to keep your movements controlled and core engaged throughout the exercise.
Perform for the desired number of repetitions and sets.
Remember to breathe throughout the exercise, exhaling as you lift and inhale as you lower your body. Also ensure that you perform the movement with control, avoiding any jerky motions which could cause injury or reduce the effectiveness of the exercise.
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Half Jackknife FAQs
What muscles does the Half Jackknife work?
The Half Jackknife mainly works the core. The main muscles are the rectus abdominis and obliques.
What equipment do you need for the Half Jackknife?
None. The Half Jackknife is a bodyweight exercise, so you can do it anywhere.
What are some Half Jackknife variations and alternatives?
Similar exercises include the Band Jackknife Sit-Up, Oblique Jackknife, Half Sit-Up and Half Wiper.
Training calculators
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