Squat Jumps

click on the image to view a video of this exercise.
Feet hip width or slightly further apart. Feet pointing forwards or just slightly turned out. Keeping back flat and head facing forward, bend knees until upper and lower legs are at 90 degrees. Ensure knees travel in line with feet and heels remain flat to the floor throughout. Avoid locking the knees when legs are straight.

From the lowest point jump up and try to get a decent height on each jump.