• DOI:10.1123/jsr.2013-0122
• Corpus ID: 24471663

Validity and reliability of an instrumented leg-extension machine for measuring isometric muscle strength of the knee extensors.

@article{Ruschel2015ValidityAR,
  title={Validity and reliability of an instrumented leg-extension machine for measuring isometric muscle strength of the knee extensors.},
  author={Caroline Ruschel and Alessandro Haupenthal and Gabriel Fernandes Jacomel and Heiliane de Brito Fontana and Daniel P R Santos and Robson Dias Scoz and H{\'e}lio Roesler},
  journal={Journal of sport rehabilitation},
  year={2015},
  volume={24 2}
}

• C. Ruschel, A. Haupenthal, +4 authors H. Roesler
• Published 13 October 2014
• Engineering
• Journal of sport rehabilitation

CONTEXT
Isometric muscle strength of knee extensors has been assessed for estimating performance, evaluating progress during physical training, and investigating the relationship between isometric and dynamic/functional performance.

OBJECTIVE
To assess the validity and reliability of an adapted leg-extension machine for measuring isometric knee extensor force.

DESIGN
Validity (concurrent approach) and reliability (test and test-retest approach) study.

SETTING
University laboratory.

PARTICIPANTS
70 healthy men and women aged between 20 and 30 y (39 in the validity study and 31 in the reliability study).

MAIN OUTCOME MEASURE
Intraclass correlation coefficient (ICC) values calculated for the maximum voluntary isometric torque of knee extensors at 30°, 60°, and 90°, measured with the prototype and with an isokinetic dynamometer (ICC2,1, validity study) and measured with the prototype in test and retest sessions, scheduled from 48 h to 72 h apart (ICC1,1, reliability study).

RESULTS
In the validity analysis, the prototype showed good agreement for measurements at 30° (ICC2,1 = .75, SEM = 18.2 Nm) and excellent agreement for measurements at 60° (ICC2,1 = .93, SEM = 9.6 Nm) and at 90° (ICC2,1 = .94, SEM = 8.9 Nm). Regarding the reliability analysis, between-days' ICC1,1 were good to excellent, ranging from .88 to .93. Standard error of measurement and minimal detectable difference based on test-retest ranged from 11.7 Nm to 18.1 Nm and 32.5 Nm to 50.1 Nm, respectively, for the 3 analyzed knee angles.

CONCLUSIONS
The analysis of validity and repeatability of the prototype for measuring isometric muscle strength has shown to be good or excellent, depending on the knee joint angle analyzed. The new instrument, which presents a relative low cost and easiness of transportation when compared with an isokinetic dynamometer, is valid and provides consistent data concerning isometric strength of knee extensors and, for this reason, can be used for practical, clinical, and research purposes.