Comparison of methods of calculating dynamic strength index

Comfort, P ORCID:, Thomas, C, Dos'Santos, T, Jones, PA ORCID:, Suchomel, T and McMahon, JJ ORCID: 2017, 'Comparison of methods of calculating dynamic strength index' , International Journal of Sports Physiology and Performance, 13 (3) , pp. 320-325.

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Purpose: To determine the reliability and variability of dynamic strength index (DSI) calculated from squat jump (SJ) (DSI-SJ) versus countermovement jump (CMJ) (DSI-CMJ) peak force (PF) and to compare DSI values between methods.
Methods: Male youth soccer and rugby league players (n = 27; age = 17.2 ± 0.7 years; height = 173.9 ± 5.7 cm; body mass = 71.1 ± 7.2 kg) performed 3 trials of the SJ, CMJ and isometric mid-thigh pull (IMTP), on two separate days. DSI was calculated by dividing the PF during each jump by the IMTP PF.
Results: DSI-SJ exhibited moderate (intraclass correlation coefficient (ICC) = 0.419) within-session reliability and high variability (percentage coefficient of variation (%CV) = 15.91) during session one; however, this improved noticeably during session two (ICC = 0.948; %CV = 4.03). Contrastingly, DSI-CMJ showed nearly perfect within-session reliability (ICC = 0.920-0.952) and low variability (%CV = 3.80-4.57) for both sessions. Moreover, DSI-SJ values demonstrated a small yet significant increase between sessions (P = 0.01, d = 0.37), whereas only a trivial and non-significant increase was observed for DSI-CMJ between sessions (P = 0.796 d = 0.07). Between-session reliability was very high for the DSI-SJ (ICC = 0.741) and nearly perfect for the DSI-CMJ (ICC = 0.924). There was no significant or meaningful difference (P = 0.261; d = 0.12) between DSI-SJ (0.82 ± 0.18) and DSI-CMJ (0.84 ± 0.15).
Conclusions: Practitioners should use DSI-CMJ as it is a more reliable measure than DSI-SJ, although it produces similar ratios.

Item Type: Article
Additional Information: Accepted author manuscript version reprinted, by permission, from International Journal of Sports Physiology and Performance, 2017, © 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:
Depositing User: Dr Paul Comfort
Date Deposited: 01 Aug 2017 08:45
Last Modified: 15 Feb 2022 22:18

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