Objectives Lower limb isometric tests are used to assess strength and strength asymmetries and monitor reductions in muscle force that may contribute to loss of performance and increase injury risk. Isometric tests in the upper body may be appropriate to monitor neuromuscular performance of the shoulder joint in sports involving contact and overhead actions. The aim of this study was to determine the reliability of a novel upper body isometric strength test.
Methods Eighteen elite rugby players (age 22.4±4.6 years; body mass 95.5±13.4 kg) were tested on consecutive days. Maximal isometric contractions using both limbs against a force platform were assessed at three angles of abduction (180°, ‘I’; 135°, ‘Y’ and 90°, ‘T’), in a prone lying position. To evaluate interday reliability, intraclass coefficients (ICC) were calculated for mean net peak force (NPF) and highest NPF achieved in any trial (peak NPF). Intratrial variability was assessed using coefficient of variation (CV), and the standard error of measurement (SEM) was used to calculate minimal detectable change (MDC).
Results Interday reliability for NPF was excellent in all test positions (ICC 0.94–0.98). The test demonstrated high absolute reliability values (SEM 4.8–10.8) and interday measurement error was below 10% in all test positions (CV 5.0–9.9%) except for the non-dominant arm I-position (CV 11.3%). Minimum detectable change was between 13.2 and 25.9 N.
Conclusion The Athletic Shoulder test demonstrated excellent reliability for each test position supporting its use as a reliable tool to quantify the ability to produce and transfer force across the shoulder girdle.
- isometric strength
- force platform
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Contributors Conception and design: all authors. Acquisition of the data: PH, LT. Analysis and interpretation: all authors. Drafting, critical revision and final approval of the article: all authors. Statistical expertise and collection and assembly of data: BA, NS, DDC. Agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved: all authors.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Disclaimer We wish to assure the editors that all authors included on this paper fulfil the criteria of authorship. We also provide our assurance that there is no one else who fulfils the criteria that has been excluded as an author.
Competing interests Daniel Cohen is a shareholder in NMP technologies Ltd. who have commercialised the ‘ForceDecks’ proprietary software used in data acquisition and analysis.
Patient consent Not required.
Ethics approval The ethics committee of the Faculty of Medicine of the University of Santander.
Provenance and peer review Not commissioned; externally peer reviewed.
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