Minimal Clinically Important Difference for Quadriceps Muscle Strength in People with COPD following Pulmonary Rehabilitation.


Oliveira A(1)(2)(3), Rebelo P(3)(4), Paixão C(3)(4), Jácome C(5)(6), Cruz J(7), Martins V(8), Simão P(9), Brooks D(1)(2), Marques A(3)(4).
Author information:
(1)School of Rehabilitation Science, McMaster University, Hamilton, ON, Canada.
(2)Respiratory Medicine, West Park Healthcare Centre, Toronto, ON, Canada.
(3)Lab3R - Respiratory Research and Rehabilitation Laboratory, School of Health Sciences, University of Aveiro
(ESSUA), Aveiro, Portugal.
(4)iBiMED - Institute of Biomedicine, Department of Medical Sciences, University of Aveiro, Aveiro, Portugal.
(5)CINTESIS -Center for Health Technology and Services Research, Faculty of Medicine, University of Porto, Porto, Portugal.
(6)Department of Community Medicine, Information and Health Decision Sciences
(MEDCIDS), Faculty of Medicine, University of Porto, Porto, Portugal.
(7)School of Health Sciences, Polytechnic Institute of Leiria, Leiria, Portugal; Centre for Innovative Care and Health Technology
(ciTechCare), School of Health Sciences
(ESSLei), Polytechnic of Leiria, Leiria, Portugal.
(8)Pulmonology Department, Hospital Distrital da Figueira da Foz, Figueira da Foz, Portugal.
(9)Pulmonology Department, Unidade Local de Saúde de Matosinhos, Matosinhos, Portugal.


Quadriceps strength training is a key component of pulmonary rehabilitation (PR). Clinical interpretability of changes in muscle strength following PR is however limited due to the lack of cut-off values to define clinical improvement. This study estimated the minimal clinically important difference (MCID) for the isotonic and isometric quadriceps muscle strength assessed with the one-repetition maximum (1RM) and hand-held dynamometry (HHD) in people with chronic obstructive pulmonary disease (COPD) following PR.A secondary analysis of a real life non-randomised controlled study was conducted in people with COPD enrolled in a 12-week community-based PR programme. Anchor and distribution-based methods were used to compute the MCIDs. The anchors explored were the St. George's respiratory questionnaire (SGRQ) and the six-minute walk test (6MWT) using Pearson's correlations. Pooled MCIDs were computed using the arithmetic weighted mean (2/3 anchor, 1/3 distribution-based methods) and reported as absolute and/or percentage of change values.Eighty-nine people with COPD (84% male, 69.9 ± 7.9 years, FEV1 49.9 ± 18.9% predicted) were included. No correlations were found between changes in 1RM and the SGRQ neither between changes in HHD and the SGRQ and 6MWT (p > 0.05). Thus, anchor-based methods were used only in the MCID of the 1RM with the 6MWT as the anchor. The pooled MCIDs were 5.7Kg and 26.9% of change for the isotonic quadriceps muscle strength with 1RM and 5.2KgF for isometric quadriceps muscle strength assessed with HHD.The MCIDs found are estimates to improve interpretability of community-based PR effects on quadriceps muscle strength and may contribute to guide interventions.