Abstract

The purpose of this study was to examine the effectiveness of 12-week plyometric training on vertical jump performance (Vj), maximal surface EMG, M-wave amplitude, Mwave latency, and nerve conduction velocity (NCV) in men volleyball player. Thirty junior high school volleyball players' volunteers (age: 17.53± 0.74; Height: 177.67± 3.14; Weight: 61.31 ± 5.32) were divided into plyometric training [PT] (n=15) and control group [c] (n=15). PT group trained so.w' but C group didn't participate in this training. Both groups were pre- and post tested in EMG, M-wave parameters, NCV and Vj test. Tow way ANOVA (group*time interaction) and Bonferroni post hoes test demonstrated significant differences (P<0.05) in PT group of pre to post test in VJ performance (9.67 %) and in M-wave latency 16.55 % t ; nerve conduction velocity 14.19 % t ; there is no significant differences in IEMG (4.6 5 % J, ) and M-wave amplitude (20.91 % t ), but there is no significant improvement during this period in control group. Comparison between groups after 12wk showed that there was a significant improvement in Latency (16.74 % J,) and NCV (19.10% t ) in PT group during the course of the study than C group (P<0.05). based on the results of this study, it is possible to conclude that coaches and trainers consider PT as a strategy for increasing volleyball players' explosive performance that this may have taken place in neuromuscular responses such as; optimizing motor unites (MU) pattern, optimizing MUs recruitment, augmentation in nerve conduction velocity, decrement in reflex excitability of the motor pool.

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