Half Jacks are one of those great filler exercises you can use to train your calves and also keep things revving as you go from one training routine to another. You can do them high-impact (jumping high) or low (keeping your rise in height to a minimum).  

What's involved: Calves, quads, lower back. 

Powered by: Calves.

Tip: For maximum benefits keep them light and fast and perform them on the balls of your feet.