Constellation, le dépôt institutionnel de l'Université du Québec à Chicoutimi

Résumé

Rationale: Although quadriceps isokinetic endurance tests are useful to study the mechanisms of lower limb muscle dysfunction in COPD, data on their reliability when performed at different angular velocities are still lacking in patients with COPD.

Objectives: to determine and compare the test-retest reliability of quadriceps isokinetic endurance testing at two knee angular velocities in patients with COPD.

Methods: After one familiarization session, 15 patients with moderate to severe COPD (age = 65 ± 1 years; FEV = 55 ± 5 % predicted) 1 performed two quadriceps isokinetic endurance tests, on two separate occasions within a 7-days interval. Quadriceps isokinetic endurance tests consisted in 30 maximal knee-extensions at angular velocities of 90°/s and 180°/s, performed in random order. Test-retest reliability was assessed for muscle endurance (muscle total work), work fatigue index (ratio of the muscle work performed during the last 10 repetitions to the work during the first 10 repetitions) and variations in dyspnea and leg fatigue Borg score from rest to end of the test. Relative reliability was determined by intraclass correlation coefficient (ICC), whereas absolute reliability was calculated from the coefficients of variation (CV) and limits of agreement expressed in % of mean difference.

Results: High relative (ICC > 0.9) and absolute test-retest reliability were identified for muscle total work at both velocities. Work fatigue index was considered reliable at 90°/s but not at 180°/s (see table 1). A lower reliability was identified for dyspnea and leg fatigue scores at both angular velocities.

Conclusions: In patients with COPD, isokinetic total work of the lower limb muscles was consistent and reproducible across the two velocities of contraction. However, work fatigue index was only reliable at the lower contraction velocity. Therefore, our results support the assessment of quadriceps endurance at an angular velocity of 90°/s in isokinetic endurance tests. Irrespective of angular velocity applied, reliability of dyspnea and leg fatigue perception was low, making their assessment during isokinetic endurance tests more uncertain.

This abstract is funded by: Fondation JD Bégin de l'Université Laval Canadian Lung Association / Canadian Respiratory Health Professionals