Intra-session reliability and criterion validity of belt-fixated crane scale knee strength measures at different knee flexion angles

Spudić, Darjan (author), Samardžija, Aleksandar (author), Oder, Bine (author), Pori, Primož (author)

This study aimed to assess the intra-session reliability of knee extension, flexion, and the flexion-to-extension isometric strength ratio using a belt-fixated crane scale protocol at 60° and 90° knee flexion angle positions. Validity was examined by comparison with a gold-standard rigid-chair isometric knee dynamometer. Twenty-six physical education students completed the testing. Both protocols showed good-to-excellent reliability for maximal strength (peak torque in Nm/kg) and flexor-to-extensor ratios at both angles (ICC$_{2.1}$ ≥ 0.84; CV% ≤ 8.2). Strength values were lower at 90° compared to 60° (p < .05). The crane scale overestimated knee flexion strength (6–9%) and flexor-to -extensor ratios (51–54% vs. 40–44%), but underestimated extension strength (16–18%). Strength measures correlated significantly between devices and angles (r from 0.52 to 0.86), but no significant correlations were found for ratios. Findings suggest that testing device and knee flexion angle substantially affect outcomes and should not be used interchangeably.

• Language: English
• Keywords: sport, muscle force, joint torque, dynamometry, peak torque, agonist-to-antagonist ratio
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FŠ - Faculty of Sport
• Publication status: Published
• Publication version: Version of Record
• Year: 2026
• Number of pages: 15 str.
• Numbering: iss. , Vol.
• PID: 20.500.12556/RUL-184527
• UDC: 796.01
• ISSN on article: 1532-7841
• DOI: 10.1080/1091367X.2026.2627981
• COBISS.SI-ID: 268776451
• Publication date in RUL: 09.07.2026

Record is a part of a journal

• Title: Measurement in physical education and exercise science
• Shortened title: Meas. phys. educ. exerc. sci.
• Publisher: Taylor & Francis
• ISSN: 1532-7841
• COBISS.SI-ID: 521553689

Licences

• License: CC BY-NC-ND 4.0, Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
• Link: http://creativecommons.org/licenses/by-nc-nd/4.0/
• Description: The most restrictive Creative Commons license. This only allows people to download and share the work for no commercial gain and for no other purposes.

Secondary language

• Language: Slovenian
• Keywords: šport, mišična sila, navor sklepa, dinamometrija, največji navor, razmerje med agonisti in antagonisti

Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P5-0147
• Name: Kineziologija monostrukturnih, polistrukturnih in konvencionalnih športov