Muscle Plasticity Following Plyometric And Combined (Plyometric And Resistance) Training

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's 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. PURPOSE: The aim of this study was to compare, 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 + plyomteric training program and the effects on jump strategy and performance. METHODS: Twenty-two male Handball players, between the ages of 17 and 24, and in good health volunteered for this study. Participants were divided into three groups. Two were trained groups (weight training and weight training combined with plyometric training) and one was a control group (baseline). For the non-combined group, exercises were performed four times a week over the 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, subjects performed the same training, and we added 6 sets of ten repetitions of plyometric training. RESULTS: After three weeks of training only combined training increased maximal voluntary force, squat jump and countermovement jump performance (p<0.05). However, weighttraining group presented no significant changes after three weeks of weight training, although there were slight increases. At the end of the 6-week training programs, the two training group 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 (p<0.05). The electromyographic data analyses indicated that the SJ and CMJ 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. CONCLUSIONS: The present study confirms the idea that a short training program can alter nervous system function. From a practical aspect our study suggests that changes in maximal strength and/or explosive strength do not produce automatic changes in combined movement such as CMJ.