Stand relaxed with your feet hip-width apart, knees soft, arms loose by your sides. Rise onto the balls of your feet and bounce lightly, shifting your weight from foot to foot in an easy rhythm - like a boxer between rounds. Stay springy and low: the bounce comes from your ankles and calves, your heels kiss the floor between beats, and everything above the waist stays relaxed.

Works: calves, quads, hip flexors

Breathing: Relaxed and rhythmic, in time with the bounce - if you can't hold a conversation, slow down.

Common Mistakes: Landing flat-footed or back on the heels, bouncing with stiff, locked knees, and tensing the shoulders up instead of letting the arms hang loose.

Make Easier: Slow the rhythm and keep the bounce small, or take the impact out entirely by shifting your weight from foot to foot without leaving the floor.

Make Harder: Pick up the tempo and lift the knees a little with each bounce, or move on to Hops on the Spot or Half Jacks.