Assessing isometric kicking force and post-match responses using the Kicker test

ABSTRACT

This study examined the inter-session reliability of force output from a novel isometric strength assessment protocol (the Kicker); and its suitability to monitor soccer player’s combined hip flexion and knee extension force capacity over 72-h post-competitive matches. Reliability (Part-A) testing was completed over three sessions on 20 individuals participating in various sports at a recreational level or higher. Post-match strength response (Part-B) data were collected for 72-h after a game (24-h (+24), 48-h (+48) and 72-h (+72) post-match) in 17 male academy soccer players. After familiarisation, Kicker force for each limb showed high inter-session reliability (ICC >0.95; typical error <14 N, CV <6%); minimum detectable change at a 95% confidence interval <40 N). Across the 72-h post-match period, Kicker force for each limb was suppressed compared to baseline (force loss range = −5.8% to −12.5%; effect sizes range = −0.26 to −0.43) at all time points. The Kicker assessment protocol measures combined isometric hip flexor and knee extensor force capacity with high inter-session reliability. The proof of concept that the protocol can be used as a monitoring tool was evidenced by sustained suppression of baseline force capacity in both kicking limbs for 72-h post soccer matches.

KEYWORDS:

• Muscle strength
• measurement
• muscle injury
• quadricep

Acknowledgments

The authors thank Melbourne Victory Football Club coaches and players for their co-operation and participation in this study. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. The ForceFrame was provided free of charge to the research team by Vald Performance. The authors would also like to thank Richard Johnston for his assistance with the statistical analysis conducted for this manuscript.

Disclosure statement

Dr David Opar is listed as a co-inventor on a patent, filed by the Queensland University of Technology (QUT), for a field-testing device of eccentric hamstring strength, which is now known commercially as the NordBord. Dr Opar has received revenue distributions from QUT based on revenue that QUT has generated through the commercialisation of his intellectual property.

Dr Opar is a minority shareholder in Vald Performance Pty Ltd, the company responsible for commercialisation of the NordBord, the ForceFrame, as well as other devices. Dr Opar has received research funding from Vald Performance, for work unrelated to the current manuscript. Dr Opar was previously the Chair of the Vald Performance Research Committee, a role that was unpaid.

Dr Opar has family members who are minor shareholders and/or employees of Vald Performance.

Dr Morgan Williams is a member of the Vald Research Committee. Dr Morgan Williams has been provided donations of equipment, and funds for travel and subsidence by Vald Performance to conduct research unrelated to this project. Dr Morgan Williams has received payment for reports for Vald Performance unrelated to this and any research study.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

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Funding

The author(s) reported there is no funding associated with the work featured in this article.