Test-retest reliability of lower limb isokinetic endurance in COPD: A comparison of angular velocities

Abstract

Background

The purpose of this study was to determine and compare the test-retest reliability of quadriceps isokinetic endurance testing at two knee angular velocities in patients with chronic obstructive pulmonary disease (COPD).

Methods

After one familiarization session, 14 patients with moderate to severe COPD (mean age 65±4 years; forced expiratory volume in 1 second (FEV₁) 55%±18% predicted) performed two quadriceps isokinetic endurance tests on two separate occasions within a 5–7-day interval. Quadriceps isokinetic endurance tests consisted of 30 maximal knee extensions at angular velocities of 90° and 180° per second, performed in random order. Test-retest reliability was assessed for peak torque, muscle endurance, work slope, work fatigue index, and changes in FEV₁ for dyspnea and leg fatigue from rest to the end of the test. The intraclass correlation coefficient, minimal detectable change, and limits of agreement were calculated.

Results

High test-retest reliability was identified for peak torque and muscle total work at both velocities. Work fatigue index was considered reliable at 90° per second but not at 180° per second. A lower reliability was identified for dyspnea and leg fatigue scores at both angular velocities.

Conclusion

Despite a limited sample size, our findings support the use of a 30-maximal repetition isokinetic muscle testing procedure at angular velocities of 90° and 180° per second in patients with moderate to severe COPD. Endurance measurement (total isokinetic work) at 90° per second was highly reliable, with a minimal detectable change at the 95% confidence level of 10%. Peak torque and fatigue index could also be assessed reliably at 90° per second. Evaluation of dyspnea and leg fatigue using the modified Borg scale of perceived exertion was poorly reliable and its clinical usefulness is questionable. These results should be useful in the design and interpretation of future interventions aimed at improving muscle endurance in COPD.

Keywords:

• chronic obstructive pulmonary disease
• lower limb
• isokinetic endurance
• test-retest reliability

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Efficacy and safety of once-daily glycopyrronium in predominantly Chinese patients with moderate-to-severe chronic obstructive pulmonary disease: the GLOW7 study [Corrigendum]

Acknowledgments

FR was supported by the Canadian Respiratory Health Professionals Fellowship (Canadian Lung Association), VC is a recipient of a research training award from the Fonds de recherche du Québec-Santé, and FM holds a Glaxo-SmithKline/Canadian Institutes of Health research Chair on COPD at Université Laval. This work was supported by the Canadian Lung Association and by le Fonds de recherche sur les maladies respiratoires J.-D.-Bégin et P.H.-Lavoie. The authors are grateful to Eric Nadreau for his technical support during the exercise testing, and to Serge Simard for his assistance with the statistical analysis.

Disclosure

The authors report no conflicts of interest in this work.