The best way to improve your vertical leap is by performing jump-specific training called plyometrics. However, you can use a variety of strength-building exercises to supplement your jumping training and improve your general leg power, which will also increase your jumping ability. Jumping is a maximal effort activity, so to improve your jumping ability you should focus on lifting heavy weights and performing low repetitions, from one to six, but always using good technique to minimize your risk of injury.
Leg press machines provide support so you are free to focus on lifting maximal weights. The movement of the leg press is very similar to performing squats and will strengthen all of your jumping muscles.
Lie in the leg press machine with your feet around shoulder-width apart. Your weight should be distributed evenly between your toes and heels. Bend your legs and lower the weight as far as you can without allowing your lower back to round, as this can increase your risk of injury. Push the weight back up and repeat. Lower the weight slowly but focus on driving the weight back up explosively to replicate the power required for jumping.
Leg extensions target your quadriceps muscles on the front of your thigh. These muscles are responsible for extending your knee. Strengthening your quadriceps may help you jump higher.
Sit on the leg extension machine with your knees in line with the lever arm pivot point. Place your ankles behind the leg restraint pad. Extend your legs until your knees are fully extended and then bend your legs and lower the weight back down. Do not allow the weights to touch between repetitions, as this will provide a short rest between reps and reduce the effectiveness of the exercise.
Your hamstrings are located on the back up your thigh and are responsible for driving your thigh down and back to generate vertical thrust. Although the curl extension works your hamstrings using a different movement pattern, increasing the general strength of your hamstrings can increase your jumping ability.
Sit on the leg curl machine with your legs straight, knees in line with the lever arm pivot point and the back of your ankles resting on the leg restraint pad. With your thighs locked in place, bend your knees and pull your feet down and back under your butt. Slowly extend your legs and repeat. Do not allow the weights to touch between repetitions.
Standing Calf Raises
Your calf muscles are small but important jumping muscles. Their main job is extending your ankle as you drive off the floor.
Stand with the balls of your feet on the step of the calf raise machine and your shoulders beneath the shoulder pads. Stand up straight with your legs locked, core tight and head facing forward. Lower your heels as far below your toes as your flexibility allows and then push up onto your tip-toes -- imagine you are peeping over a high wall.
Because strength-training machines can very in design and therefore may operate differently, check with a qualified gym instructor or personal trainer if the machine you are going to use is different from those described previously.