{
  "abstract": "Background Quadriceps maximal voluntary contraction (QMVC) reliably measures quadriceps muscle force and predicts mortality in chronic obstructive pulmonary disease (COPD). However, the minimal important difference (MID) of QMVC is not well-established.Aim To estimate the MID of QMVC parameters in people with COPD following pulmonary rehabilitation (PR).Methods QMVC was measured before and after 8 weeks of outpatient PR in people with COPD. Absolute and % change in QMVC, and change in normalised QMVC were calculated using paired t-tests. Anchor and distribution-based methods (0.5×SD change, SEM, minimal detectable change at 95% confidence, effect size and 1.96 SEM) were used to estimate the MID.Results Of 903 participants, 383 were excluded due to PR non-completion or missing QMVC data with 520 included in the analysis (37% female; mean (SD) age 70.2 (8.4) years; forced expiratory volume in 1 s 51.4 (21.4)% predicted). QMVC parameters increased with PR; mean (95% CI) or mean (SD) change: QMVC 2.0 kg (1.5 kg to 2.5 kg), 10.6% (27.7%) and normalised QMVC 5.0% predicted (3.9% to 6.2%). Anchor-based MID estimates were precluded due to weak/no correlation with external anchors. Using distribution-based methods, the MID for QMVC change, QMVC % change and normalised QMVC change were estimated as mean (range) 3.55 kg (1.84 kg to 5.11 kg), 18.34% (9.60% to 26.60%) and 7.78% (3.78% to 12.48%) for all participants. However, MID estimates for absolute and % change in QMVC differed markedly between men and women. Normalised QMVC estimates demonstrated smaller sex-based discrepancies.Conclusion We provide MID estimates for QMVC parameters. Sex-specific or normalised MID estimates for QMVC should be used to facilitate the interpretation of change.",
  "authors": [
    {
      "affiliations": [
        "Harefield Respiratory Research Group, Royal Brompton and Harefield Hospitals, Guy’s and St Thomas’ NHS Foundation Trust, London, UK",
        "College of Health Medicine and Life Sciences, Brunel University London, Uxbridge, UK"
      ],
      "name": "Timothy O Jenkins"
    },
    {
      "affiliations": [
        "Harefield Respiratory Research Group, Royal Brompton and Harefield Hospitals, Guy’s and St Thomas’ NHS Foundation Trust, London, UK"
      ],
      "name": "George D Edwards"
    },
    {
      "affiliations": [
        "Harefield Respiratory Research Group, Royal Brompton and Harefield Hospitals, Guy’s and St Thomas’ NHS Foundation Trust, London, UK",
        "Imperial College London National Heart and Lung Institute, London, UK"
      ],
      "name": "Suhani Patel"
    },
    {
      "affiliations": [
        "Harefield Respiratory Research Group, Royal Brompton and Harefield Hospitals, Guy’s and St Thomas’ NHS Foundation Trust, London, UK"
      ],
      "name": "Jane Canavan"
    },
    {
      "affiliations": [
        "Hillingdon Hospitals NHS Foundation Trust, London, England, UK"
      ],
      "name": "Samantha S C Kon"
    },
    {
      "affiliations": [
        "Health Innovation West of England Future Space, Bristol, UK"
      ],
      "name": "Ruth E Barker"
    },
    {
      "affiliations": [
        "Harefield Respiratory Research Group, Royal Brompton and Harefield Hospitals, Guy’s and St Thomas’ NHS Foundation Trust, London, UK"
      ],
      "name": "Sarah E Jones"
    },
    {
      "affiliations": [
        "Harefield Respiratory Research Group, Royal Brompton and Harefield Hospitals, Guy’s and St Thomas’ NHS Foundation Trust, London, UK"
      ],
      "name": "Jessica A Walsh"
    },
    {
      "affiliations": [
        "Harefield Pulmonary Rehabilitation Unit, Royal Brompton and Harefield Hospitals, Guy's and St Thomas' NHS Foundation Trust, Harefield, UK"
      ],
      "name": "Karen A Ingram"
    },
    {
      "affiliations": [
        "Kings College London, London, UK"
      ],
      "name": "Matthew Maddocks"
    },
    {
      "affiliations": [
        "Respiratory Medicine, Royal Brompton and Harefield Hospitals, London, England, UK"
      ],
      "name": "Michael I Polkey"
    },
    {
      "affiliations": [
        "College of Health Medicine and Life Sciences, Brunel University London, Uxbridge, UK"
      ],
      "name": "Claire Marie Nolan"
    },
    {
      "affiliations": [
        "Harefield Respiratory Research Group, Royal Brompton and Harefield Hospitals, Guy’s and St Thomas’ NHS Foundation Trust, London, UK",
        "Imperial College London National Heart and Lung Institute, London, UK",
        "Harefield Pulmonary Rehabilitation Unit, Royal Brompton and Harefield Hospitals, Guy's and St Thomas' NHS Foundation Trust, Harefield, UK",
        "Kings College London, London, UK",
        "Respiratory Medicine, Royal Brompton and Harefield Hospitals, London, England, UK"
      ],
      "name": "William Man"
    }
  ],
  "title": "Minimal important difference of quadriceps maximal voluntary contraction (QMVC) in COPD: a prospective cohort study",
  "uid": "8149a0bf-a8b9-5abb-82c7-355e0e763c17"
}