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

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  • George C. Dallas
  • Panagiotis Pappas
  • Constantinos G. Ntallas
  • Giorgos P. Paradisis
  • Dr Timothy Exell
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.
Original languageEnglish
Pages (from-to)979-984
JournalJournal of Sports Medicine and Physical Fitness
Issue number7
Publication statusPublished - 1 Jun 2020


  • The effect of four weeks

    Rights statement: This is a postprint version of the article published in The Journal of Sports Medicine and Physical Fitness. This version is free to view and download to private research and study only. Not for redistribution or re-use. ©Edizioni Minerva Medica. The final published article is available online on Minerva Medica website at 10.23736/S0022-4707.20.10384-0. Cite this article as Dallas GC, Pappas P, Ntallas CG, Paradisis GP, Exell TA. The effect of four weeks of plyometric training on reactive strength index and leg stiffness is sport dependent. J Sports Med Phys Fitness 2020;60:979-84. DOI: 10.23736/S0022-4707.20.10384-0.

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    Due to publisher’s copyright restrictions, this document is not freely available to download from this website until: 1/06/21

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