Table 1– Subject characteristics.
| Healthy | COPD | p-value | |
| Subjects | 10 | 101 | |
| Males/females | 4/6 | 60/41 | 0.20 |
| Age years | 68.0±7.3 | 64.8±7.6 | 0.21 |
| Height cm | 166±9 | 169±9 | 0.42 |
| Weight kg | 75.8±14.6 | 70.0±15.1 | 0.25 |
| Body mass index kg·m−2 | 27.2±3.7 | 24.5±4.8 | 0.09 |
| Fat mass kg | 22.4±9.7 | 27.0±6.0 | 0.15 |
| Fat-free mass kg | 48.8±12.1 | 47.7±9.0 | 0.71 |
| Fat-free mass index kg·m−2 | 16.9±2.7 | 16.8±2.4 | 0.85 |
| Current/former/never-smoker | 1/4/5 | 25/76/0 | <0.01 |
| Smoking pack-years | 10±15 | 49±24 | <0.01 |
| FEV1 L | 2.59±0.64 | 1.08±0.54 | <0.01 |
| FEV1 % predicted | 106±13 | 41±20 | <0.01 |
| VC L | 3.72±0.95 | 3.00±0.79 | <0.01 |
| VC % predicted | 121±19 | 89±19 | <0.01 |
| FEV1/VC | 69.9±5.7 | 35.8±13.8 | <0.01 |
| TLC L | 5.97±1.32 | 7.34±1.74 | 0.02 |
| TLC % predicted | 105±11 | 123±19 | <0.01 |
| RV L | 2.31±0.55 | 4.26±1.49 | <0.01 |
| RV % predicted | 102±12 | 189±60 | <0.01 |
| RV/TLC | 39±6 | 56±12 | <0.01 |
| TLCO L | 6.79±1.52 | 3.49±1.58 | <0.01 |
| TLCO % predicted | 87±13 | 42±19 | <0.01 |
| PCO2 kPa | 5.34±0.47 | 5.20±0.70 | 0.55 |
| PO2 kPa | 11.28±1.02 | 9.61±1.53 | <0.01 |
| GOLD stage I/II/III/IV | 4/26/31/40 | ||
| GOLD grade A/B/C/D | 9/4/19/69 | ||
| Exacerbations in the past year | 1 (0–2) | ||
| Medication n (%) | |||
| Long-acting β-agonist | 85 (84) | ||
| Inhaled corticosteroid | 85 (84) | ||
| Oral steroid >5 mg·day−1 | 8 (8) | ||
| Oxygen | 18 (18) | ||
| Nocturnal NIV | 8 (8) | ||
| SGRQ | 8.2±9.9 | 49.9±19.0 | <0.01 |
| QMVC kg | 31.5±9.2 | 26.7±7.4 | 0.05 |
| Quadriceps twitch force kg | 7.4±2.1 | 9.7±3.1 | 0.04 |
| Body composition (both thighs) | |||
| MTCSA cm2 | 221.8±44.9 | 190.9±47.6 | 0.04 |
| Lean tissue cross-sectional area cm2 | 212.1±42.5 | 178.0±44.4 | 0.02 |
| Lean tissue HU | 42.3±4.0 | 41.5±4.8 | 0.63 |
| Intramuscular fat cm2 | 11.8±5.1 | 13.0±7.4 | 0.64 |
| Intramuscular fat % | 4.30±1.23 | 6.64±3.32 | 0.03 |
| Fibre type %# | |||
| I | 48.9±9.7 | 28.2±12.5 | <0.01 |
| IIa | 44.3±8.5 | 57.0±13.4 | 0.01 |
| IIx | 3.2±4.6 | 12.1±13.1 | 0.02 |
| II | 47.5±10.1 | 67.9±15.2 | <0.01 |
| Exercise capacity# | |||
| 6MWD m | 572±81 | 341±141 | <0.01 |
| ISWT m | 250±132 | ||
| Physical activity# | |||
| Wear time h per day | 23.6±0.5 | ||
| Wear time % | 98.3±0.2 | ||
| TEE kcal per day | 1976±332 | ||
| Steps per day | 4501±3273 | ||
| PAL | 1.41±0.17 |
Data are presented as n, mean±sd or median (interquartile range), unless otherwise stated. COPD: chronic obstructive pulmonary disease; FEV1: forced expiratory volume in 1 s; VC: vital capacity; TLC: total lung capacity; RV: residual volume; TLCO: transfer factor of the lung for carbon monoxide; PCO2: carbon dioxide tension; PO2: oxygen tension; GOLD: Global Initiative for Chronic Obstructive Lung Disease; NIV: noninvasive ventilation; SGRQ: St George’s respiratory questionnaire; QMVC: quadriceps maximum voluntary contraction; MTCSA: mid-thigh cross-sectional area; 6MWD: 6-min walking distance; ISWT: incremental shuttle walk test; TEE: total energy expenditure; PAL: physical activity level. #: COPD fibre type n = 48, ISWT n = 30, 6MWD and physical activity n = 69.