To develop vertical jumping ability, some scientists have claimed that free jumping is more effective than weight training (squatting) and that the combination of free jumping and weight training is most effective. In this study, high school students were involved in special training programs (hereafter referred to as "suspension training"), an idea borrowed from speed assisted training (tow training) in running. This training involved the students vertical jumping with all their might while they were pulled upward by rubber ropes attached to their hip belts. Twenty male volleyball players (Age: average}SD=15.75}0.72 years) were divided into 3 groups. The first group was involved in free jumping, the second and the third groups were involved in suspension training with an upward pulling force of 10% and 20% of their body weights respectively. They jumped 10 times a day with 30 second rests between the jumps, 3 days a week for 10 weeks in addition to their regular volleyball training. After 10 weeks of training, the vertical jumping ability of the first group increased 3.43}0.50 cm (4.94}0.71%), the second group 7.88}2.47 cm (12.69}7.05%), and the third group 9.60}3.01 cm (15.35}4.56%), respectively. The difference between the average increment in vertical jumping distance of the free jumping group and that of the suspension training group was statistically significant (p0.001). Differences in the results between the 10% assisted group and the 20% assisted group were insignificant, however.
Introduction:
As vertical jumping ability is essential in many sports activities, athletes and coaches devote themselves to developing this ability by strengthening leg muscle groups through weight training (squatting, leg extension, etc.) and plyometric training (depth jump, drop jump, etc.) . In weight training, to gain muscle strength a heavy load is usually utilized in accordance with the overload principle which states that to develop muscle strength effectively the load has to exceed certain weight limits such as 80%Max or 10 RM. It is reported, however, that static (isometric) but active (isotonic and isokinetic) weight training is not effective in improving jumping ability even though it strengthens the muscles. One of the most popular methods of weight training for the leg muscles of athletes is the squatting. Although this training method is effective, it is apt to cause knee injuries and is sometimes dangerous.
According to the fundamental law of physics, the jumping height which a jumper can reach is determined by the vertical component of the jumper's takeoff velocity. So vertical jumping ability is directly related to the power output of the jumper's leg muscles because the power output is the product of velocity (speed of the muscle contraction) and strength. Therefore, not only strength training but also speed training is supposed to be an important factor in improving vertical jumping ability.
The authors have previously conducted an experiment on tow-training for runners. In the experiment, the runners were towed by an automobile on a track and forced to run about 10% faster than their maximum speed for some distances. The results in this experiment suggested that to run fast one should run faster in training. This theory was assumed to be applicable to vertical jumping, i.e., to jump up fast the jumper should experience a faster jumping in training. Tohji et al. reported that between two training groups, free-jumping training and squat training groups, the free-jumping training group attained more increment in jumping height than the squat training group after 8 weeks of training. They concluded that free-jumping might be more appropriate in developing a jumper's takeoff velocity than squat training.
It was conceivable to the authors that a jumper would take off faster and jump higher if the jumper was assisted when he takes off by being pulled upward by a spring or a rubber tubing. And it was believed that by repeating this training (hereafter referred to as a "suspension training"), eventually the jumper's legs might learn how to jump up faster and jump higher even without being assisted. Accordingly, the purpose of this study was to examine the effect of suspension training in developing vertical jumping ability and compare the effect with result from free-jumping training.
Methods:
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