Toumi, H., & Best, T. (2004). Muscle plasticity following plyometric and combined (plyometric and resistance) training. Medicine and Science in Sports and Exercise, 36(5), Supplement abstract 1153.

"It has been demonstrated that muscle jump performance can be increased in response to plyometric training lasting from 4-12 weeks. Researchers who investigate the transference of plyometric training to jump performance appear to be entrenched in two camps. One suggests that plyometric training needs to increase the degree of coordination and maximize the ability to use the muscle stretch-shortening cycle. The other proposes that there is no need for specificity, but plyometric training improves power and vertical jump performance because it increases muscle contraction force" (p. S169). In a short training study, the changes in central and peripheral properties of the leg extensors derived from maximal resistance training and a combined resistance plus plyometric training program, and the effects on jump strategy and performance were compared. Male handball players (N = 22) were divided into three groups. Two were trained (weight training and weight training plus plyometric training) and one was a control group. For the weight-training group, exercises were performed four times a week over an eight-week period. Exercise consisted of six sets of ten repetitions at 70% of the maximal isometric force output of the leg press with three minutes of rest between series. For the combined group, Ss performed the same training, with an added six sets of ten repetitions of plyometric training.

After three weeks of training only combined training increased maximal voluntary force, squat jump, and countermovement jump performance. At the end of six weeks, the two training groups increased maximal isometric force and squat jump performance. However, only combined training presented a significant increase in height-jump performance and joint knee stiffness during the countermovement jump. The electromyographic data analyses indicated that the squat jump and countermovement jump were performed similarly before and after the training period for the weight training group. However, the combined group presented an increase in IEMG values during the contact and concentric phase.

[Note: It should be noted that the combined group did more training than the other two groups and the implied causes revealed here might be due to training volume rather than training content.]

Implication. A short resistance-training program can alter nervous system function. Changes in maximal strength and/or explosive strength do not produce automatic changes in a complex movement such as the countermovement jump.

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