Starting with tall posture, engage your core muscles below the belly button by drawing the lower ab muscles inward toward the spine. Avoid arching the low back. With arms in a ready position do a one-legged squat with your body weight distributed equally over the foot. Don’t go any lower than a ninety degree bend in the knee, keeping your knee in alignment with your second toe over your heel as much as possible. Then when you straighten back up, use your buttock and thigh muscles jumping straight up reaching your arms high up into the air. Remember to keep your inner core engaged while you do the one-legged jump squats. Do 3 sets, 10 to 15 repetitions each. This is a great strengthening exercise for the core and balance and proprioception with quad and posterior hip muscles. It will also help prevent ACL knee injuries while giving you a better jumping vertical.