Influence of reactive strength index modified on force- and power-time curves

McMahon, JJ ORCID: https://orcid.org/0000-0001-9952-7846, Jones, PA ORCID: https://orcid.org/0000-0002-3295-7670, Suchomel, TJ, Lake, J and Comfort, P ORCID: https://orcid.org/0000-0002-1131-8626 2017, 'Influence of reactive strength index modified on force- and power-time curves' , International Journal of Sports Physiology and Performance, 13 (2) , pp. 220-227.

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Abstract

Purpose: The reactive strength index modified (RSImod) has been recently identified and validated as a method of monitoring countermovement jump (CMJ) performance. The kinetic and kinematic mechanisms that optimize a higher RSImod score are, however, currently unknown. The purpose of this study, therefore, was to compare entire CMJ force-, power-, velocity- and displacement-time curves (termed temporal phase analysis) of athletes who achieve high versus low RSImod scores.
Methods: Fifty-three professional male rugby league players performed three maximal effort CMJs on a force platform and variables of interest were calculated via forward dynamics. RSImod values of the top (high RSImod group) and bottom (low RSImod group) twenty athletes’ kinetic and kinematic-time curves were compared.
Results: The high RSImod group (0.53±0.05 vs. 0.36±0.03) jumped higher (37.7±3.9 vs. 31.8±3.2 cm) with a shorter time to take-off (TTT) (0.707±0.043 vs. 0.881±0.122 s). This was achieved by a more rapid unweighting phase followed by greater eccentric and concentric force, velocity and power for large portions (including peak values) of the jump, but a similar countermovement displacement. The attainment of a high RSImod score therefore required a taller, but thinner, active impulse.
Conclusion: Athletes who perform the CMJ with a high RSImod, as achieved by high jumps with a short TTT, demonstrate superior force, power, velocity and impulse during both the eccentric and concentric phases of the jump. Practitioners who include the RSImod calculation within their testing batteries may assume that greater RSImod values are attributed to an increase in these underpinning kinetic and kinematic parameters.

Item Type:	Article
Additional Information:	Accepted author manuscript version reprinted, by permission, from International Journal of Sports Physiology and Performance, 2017, https://doi.org/10.1123/ijspp.2017-0056. © Human Kinetics, Inc.
Schools:	Schools > School of Health and Society > Centre for Health Sciences Research
Journal or Publication Title:	International Journal of Sports Physiology and Performance
Publisher:	Human Kinetics
ISSN:	1555-0265
Related URLs:	Publication
Depositing User:	Dr John J McMahon
Date Deposited:	26 Jul 2017 08:58
Last Modified:	15 Feb 2022 22:17
URI:	https://usir.salford.ac.uk/id/eprint/43294

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