In - Out Plank

Beginners or persons with lower back pain should avoid this exercise.

Place your forearms on the floor, with your elbows directly under your shoulders, both feet extended back behind you.

Exhale and lift your body from the ground, aiming to make a straight line from your ear - shoulder - hip and knee, both feet on the floor.

Once in the standard Plank position, slowly bring one knee up to your side at hip levels, fixing it in place by keeping your abdominal - lower back and buttock muscles contracted throughout.

You may decide you want to hold this position, or alternatively slowly take the leg in and out, whilst keeping the foot off the floor.

Intermediates should aim to work each side for 2 reps, aiming to gradually increase the time in each position, when they next perform the exercise.

Advanced work as above for 1 rep each side, then perform again with the foot in and out movement, working at a rate of 2 - 2 - 2. This simply means 2 seconds to bring the knee to your side, hold it there for 2 seconds, then 2 seconds to return it back.

Adjusting both your hand and foot position will alter the exercise difficulty; wide leg stance will give greater stability, whilst having your hands together will reduce stability.