The Prone Jackknife is a great core exercise for strengthening the hip flexor’s, abdominals and shoulder girdle.

1. In a push-up position, place your feet on the ball

2. Hold your spine straight and maintain head and neck alignment

3. Draw your knees in towards your chest for the duration of two seconds without altering the curves in your back.

4. Return to the start position over the duration of two seconds.

5. Repeat the exercise for 1-3 sets of 8-12 reps.

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Please see my video demonstration below for more information: