Lie on your front with your lower legs on a stability ball.
Support yourself on your forearms with your elbows under your shoulders.
Tighten your abdominal and buttock muscles and look straight down between your hands as you lift yourself up into a plank position.
Keep your knees straight throughout this exercise as you aim to hold a straight line from your shoulders to your feet.
Next, attempt to lift one straight leg up and hold the plank.
The aim is to maintain this position without any movement in the ball.
Lower the leg and repeat with the other side.
