Stand tall with your core braced and a flat back. This is your start position. Take a big step forward with your right leg and bend at the knee, lowering your body until your front knee is bent at least 90 degrees, whilst your rear knee should be hovering just off the floor. Inhale as you do so. At the bottom of the movement, push off from your right foot explosively, extend your knee and hip and bring your right knee to your chest. Repeat the movement for the required number of reps (or time) on one side and then alternating legs.