One minute of intense effort followed by one minute rest. Repeat three times. Total: six minutes. Start standing upright, with your feet roughly shoulder-width apart. Keep your arms out in front of your chest (position 1).
Bring your body down into a high squat to create some force, then jump directly into the air, bringing your knees up towards your chest area (position 2).
Land and repeat, trying to get your knees as high as possible. Be sure to bend your knees as you return to the ground to prevent any ankle injuries.