Related Experiment Video
Updated: Aug 15, 2026
Lower Limb Biomechanical Analysis of Healthy Participants
Published on: April 15, 2020
Reliability and validity of static knee strength measurements obtained with a chair-fixed dynamometer in subjects
Dany Gagnon1, Sylvie Nadeau, Denis Gravel
1Hôpital de Réadaptation Lindsay, Montréal, QC, Canada. danygagnon@ssss.gouv.qc.ca
Objectives:
To evaluate the reliability (intertrial, interevaluator) and the concurrent validity of strength measurements obtained with a chair-fixed dynamometer and to recommend a clinical protocol that minimizes standard error of measurement (SEM).
Design:
Within-session repeated measures of maximal static strength of knee flexors and extensors at 30 degrees and 60 degrees of flexion on the chair-fixed and Cybex dynamometers.
Setting:
Ambulatory physiotherapy department of a rehabilitation hospital.
Participants:
Convenience sample of 50 subjects with total hip (n=25) or knee (n=25) arthroplasty.
Interventions:
Not applicable.
Main Outcome Measures:
Reliability was quantified by indices of dependability and corresponding SEMs estimated with the generalizability theory, whereas coefficients of correlation were used to assess the validity.
Results:
Indices of dependability confirmed excellent intertrial (0.98-1.00) and a very good interevaluator (.92-.99) reliability for the strength measures obtained for different movements and positions. An average of 3 trials minimized the magnitude of the SEMs (>2 Nm for all measurements). When comparing the strength values obtained with the Cybex dynamometer to those measured with the chair-fixed dynamometer, strongest relations were attained when the tested knee was positioned at 60 degrees compared with 30 degrees for subjects with a total knee (.78-.92 vs .87-.93) or hip (.73-.85 vs .86-.91) arthroplasty.
Conclusions:
A clinical protocol averaging 3 trials with the knee positioned at 60 degrees after a familiarization period, both for knee flexors and extensors, performed by a trained therapist is recommended to minimize measurement errors on strength values measured with the chair-fixed dynamometer.
