by Dr. Darrell M. Schreyer, D.C.
Volleyball and basketball are two sports that require a lot of jumping. The average player will leave the ground between 100 and 150 times per game in volleyball, and somewhat less in basketball. In the past good jumpers were considered "naturals" who did not need to train. Nobody thought much about improving jumping ability and teams merely practiced, hoping leaping height would increase through repetition. Some jumping and some weight lifting would be attempted but for the most part little concern was given to improving basic jumping skills.
Running is great for building cardiovascular fitness, jumping rope conditions the body and increases coordination, and weight training improves muscular strength and power. But nothing helps a player as much as practicing skills which are specific to that persons chosen sport. Most coaches today recognize that for maximum training effect, the exercise program must simulate conditions that will be encountered in the game.
The time to begin working on jumping ability is in high school when skills are more easily acquired and physical abilities are being developed. Many high school athletes utilize squat racks with free weights with the hope to develop leg strength and increase their vertical jump. This method is very outdated for this type of training as the element of speed is not considered. Lifting a barbell is an isotonic exercise (the muscle is contracted with a constant tension). Therefore it is limited to the maximum weight that can be lifted at the weakest angle of the range of motion. Because of the design of the skeleton and its leverage, the body doesn't have equal strength in all positions. The speed of lifting is somewhat jerky and, once the inertia of the weight is overcome, the maximum resistance isn't maintained for the rest of the movement.
The best mix is the use of speed and strength to develop the power or spring of jumping. Training can vary from jumping repetitively, with hand or ankle weights, or even rubber tubes filled with sand held across the shoulders. Many companies have developed weight training machines to train both speed and endurance. These often work on air or hydraulic power and offer constant resistance through the full range of motion.
Another proven method to develop greater leaping ability is termed plyometrics, otherwise known as "negative jumping" or "depth jumping". This is the act of jumping from a height (usually a bench) onto a mat, and quickly jumping from that position just as you normally would. The quick stretch in the opposite direction of a muscle or group of muscles just prior to the actual movement, will cause that movement to be more forceful. An example of this is the golf swing. If you don't take a back swing you don't set the muscles to quickly contract and thus cause a much more forceful action. A muscle that is shortening is much stronger if it immediately follows a stretch or lengthening of that same muscle.
The question of how great of a height to jump from is highly arguable. Most sources included a height between 62 cm. and 110 cm. Jumps from heights greater than 110 cm. were found to be counter -productive, as the speed of change from stretch to contraction of the muscle is drastically altered, and the exercise loses its effectiveness.
A good strength base should be established before an extensive plyometric program is initiated. Unless the leg strength is more than double the body weight, the athlete should concentrate on purely strength training. Also, to avoid undue discomfort or even injury, the athlete should jump down on a soft gymnastic mat or similar material.