ORIGINAL ARTICLE  EXERCISE PHYSIOLOGY AND BIOMECHANICS 

The Journal of Sports Medicine and Physical Fitness 2020 July;60(7):979-84

DOI: 10.23736/S0022-4707.20.10384-0

Copyright © 2020 EDIZIONI MINERVA MEDICA

language: English

The effect of four weeks of plyometric training on reactive strength index and leg stiffness is sport dependent

George C. DALLAS ¹ ✉, Panagiotis PAPPAS ¹, Constantinos G. NTALLAS ¹, Giorgos P. PARADISIS ¹, Timothy A. EXELL ²

¹ School of Physical Education and Sport Science, National and Kapodistrian University of Athens, Athens, Greece; ² School of Sport, Health and Exercise Science, University of Portsmouth, Portsmouth, UK

BACKGROUND: Plyometric exercises are often used to develop lower limb strength and performance-related biomechanics such as leg stiffness. However, the effectiveness of plyometric training may depend on participants’ own training and performance demands. The purpose of this study was to examine the effect of plyometric training on Reactive Strength Index (RSI) and leg stiffness (Kleg) on young athletes of different sports.
METHODS: Forty eight female athletes (25 Taekwondo (TKD) and 23 rhythmic gymnastics (RG), mean±SD: age: 8.94±2.50 years; mass: 29.73±7.69 kg; height: 138.84±11.90 cm; training experience: 4.62±2.37 years) participated in this study. Participants were randomly assigned to experimental (PT, N.=24) and control (CG, N.=24) groups. The PT group followed a twice-weekly plyometric training program for 4 weeks. Plyometric drills lasted approximately 5-10 s, and at least 90 s rest was allowed after each set. To examine RSI, participants performed trials of five maximal CMJs. Submaximal hopping (20 hops) was performed in order to examine leg stiffness.
RESULTS: Significant interaction effect was found for RSI and the post hoc analysis showed that RSI significantly increased by 35% (P=0.017) in RG athletes, whereas a significantly reduction by 28% (P=0.004) was revealed in TKD athletes. The interaction effect between time and group was statistically significant for Kleg (P<0.05) with Kleg significantly increasing by 31% (P=0.008) in TKD athletes, but remaining unchanged (P>0.05) in RG athletes.
CONCLUSIONS: The results showed that the effect of a 4-week plyometric training program on RSI and leg stiffness is sport dependent. Further, the applied plyometric program was effective in reducing ground contact time and therefore increasing leg stiffness.

KEY WORDS: Plyometric exercise; Gymnastics; Martial arts; Athletes