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Sports 2018, 6(3), 81; https://doi.org/10.3390/sports6030081

Reliability of and Relationship between Flight Time to Contraction Time Ratio and Reactive Strength Index Modified

1
Directorate of Sport, Exercise and Physiotherapy, University of Salford, Frederick Road, M6 6PU Salford, UK
2
Department of Sport and Exercise Sciences, University of Chichester, PO19 6PE Chichester, UK
*
Author to whom correspondence should be addressed.
Received: 31 July 2018 / Revised: 7 August 2018 / Accepted: 14 August 2018 / Published: 15 August 2018
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Abstract

Countermovement jump (CMJ) force-time testing is commonly used to monitor seasonal alterations in athletes’ CMJ strategy (to infer alterations in neuromuscular function). The flight time to contraction time (FT:CT) ratio and reactive strength index modified (RSImod) are considered to be two primary CMJ variables of interest. Due to similar calculations, it is likely that the FT:CT ratio and RSImod share similar reliability and an almost perfect relationship. Consequently, there may be no requirement to include both variables in CMJ monitoring reports. This study aimed to investigate this by recruiting twenty-five males to perform three CMJs on a force platform across two sessions that were separated by one week. The FT:CT ratio and two calculations of RSImod (based on the jump height from either flight time or take-off velocity) were then calculated using robust methods. The between-day reliability was good-excellent for all of the variables (95% confidence interval range of the coefficient of variation = 2.02–9.22%) with no significant between-day differences noted (p ≥ 0.231). There was an almost perfect positive relationship between the FT:CT ratio and RSImod regardless of the calculation method (r = 0.944–0.947, p < 0.001). As the FT:CT ratio and RSImod yield similar absolute reliability and share 90% of common variance, there is little reason to include both variables in CMJ monitoring reports. View Full-Text
Keywords: countermovement jump; jump strategy; jump height; force platform; jump monitoring countermovement jump; jump strategy; jump height; force platform; jump monitoring
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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McMahon, J.J.; Lake, J.P.; Comfort, P. Reliability of and Relationship between Flight Time to Contraction Time Ratio and Reactive Strength Index Modified. Sports 2018, 6, 81.

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