The ability to jump high is necessary not only in sports such as basketball and volleyball, but in almost all sports. For example,, this ability is needed by football receivers, tennis players for reaching and sometimes hitting an overhead, baseball and lacrosse players to catch a ball,, figure skaters in executing different stunts, and others.
There are three major leg actions that occur in jumping: hip extension, knee extension, ankle extension. The joint most ignored in training for improving jump height is ankle joint extension. Most exercises such as the squat target mainly the knee joint extension which is probably the greatest contributor to jump height.
But, this seemingly insignificant action (ankle extension) can add inches to your jump when it takes place after the hip and knee extension. In addition, more powerful ankle joint extension in your cutting and running actions will greatly improve your speed and quickness.
To strengthen the muscles involved in ankle joint extension, as displayed in a quick jump, cut, or sprint, do the explosive heel (calf) raise. However, keep in mind that the explosive version of the heel raise should be done only you after you have developed a sufficiently strong strength base. The stronger the calf muscles the more speed and explosive power that can be developed.
Heel raises are most easily done on an exercise machine. But they can also be done with free weights while standing on a raised platform or step with a barbell on the shoulders or dumbbells in the hands. Or, you can use Active Cords attached to a belt around the waist and hooked onto a beam or raised platform on which you stand.
To execute inhale and hold your breath as you lower your heels at a moderate rate of speed. As you feel a strong stretch in the Achilles tendon and calf muscle quickly switch directions and rise up as high as possible. In the ending position your heels should be raised maximally and your legs should be straight. Hold the upper most position for a count of two and then repeat.
A key element in this exercise is to lower your body under control until you feel a strong stretch of the Achilles tendon and calf muscle. At this point you should quickly reverse directions and hold at the very top position. In this exercise you create tension in the calf muscles and Achilles tendon in the down phase and then use the energy created in the up phase. This uses muscle and tendon resiliency, a key factor in quickness and jump height.
Doing the exercise with a barbell on the shoulders or dumbbells in the hands, requires considerable balance. If you cannot balance yourself well then you should do the exercise on an exercise machine with the resistance pads on your shoulders. Execution is the same. However, every so often, exercise with free weights to work on your balance as you execute ankle extension. You will not be able to use as much resistance but you will be developing greater balance in the movement.
Be sure that you keep the legs straight when you do this exercise. If you bend the knees you weaken the contraction of the gastrocnemius muscle. Understand that the gastrocnemius is a two joint muscle crossing both the ankle and knee joints and thus must be taut at the knee joint and when doing the exercise.
It is also important that you first do heel raises to strengthen the gastrocnemius muscle and Achilles tendon through a full range of motion. This is a prerequisite to doing the explosive variant. Also do toe raises with the Active Cords to strengthen the muscles on the front on the shin to balance development of the calf muscles. Doing this will allow you to develop even more strength of the calf muscles.
For more informtion on this and other exercises specific to jumping, read Explosive Basketball Training. Also see Biomechanics and Kinesiology of Exercise. The exercises are explained in detail and are accompanied with illustrative photographs.