| Rest | HEWR (60 W) | Peak | ||||
| Controls | Mild COPD | Controls | Mild COPD | Controls | Mild COPD | |
| Dyspnoea Borg scale | 0.0±0.0 | 0.1±0.2 | 0.6±0.7 | 1.4±1.4* | 6.0±3.1 | 4.7±1.8 |
| Leg discomfort Borg scale | 0.1±0.3 | 0.1±0.2 | 0.7±0.7 | 2.1±1.7** | 6.8±3.2 | 5.4±1.8 |
| V′O2 L·min−1 | 0.35±0.12 | 0.32±0.08 | 1.13±0.12 | 1.11±0.17 | 2.55±0.88 | 1.61±0.48*** |
| Work rate W | 178±62 | 102±30*** | ||||
| Heart rate beats·min−1 | 73±15 | 81±13 | 101±18 | 116±17* | 155±16 | 142±17* |
| SaO2 % | 97±1 | 97±2 | 97±1 | 96±2 | 94±3 | 95±2 |
| V′E L·min−1 | 10.4±3.6 | 11.2±3.1 | 27.7±4.3 | 33.9±8.1* | 92.7±30.1 | 55.7±16.4*** |
| VT L | 0.79±0.24 | 0.69±0.18 | 1.33±0.19 | 1.32±0.28 | 2.35±0.69 | 1.57±0.44*** |
| fR breaths·min−1 | 14.3±5.2 | 17.2±5.1 | 21.4±4.5 | 26.9±8.9* | 39.5±6.8 | 36.1±7.2 |
| V′E/V′CO2 | 40.0±4.9 | 46.3±7.6** | 28.9±2.2 | 33.3±4.0*** | 33.0±4.3 | 33.3±4.1 |
| PETCO2 mmHg | 35.1±2.7 | 32.3±3.6* | 39.9±3.2 | 35.2±4.5** | 33.6±4.0 | 33.6±3.9 |
| IC L | 3.06±0.87 | 2.56±0.61 | 3.31±0.84 | 2.53±0.52** | 3.16±0.80 | 2.29±0.46*** |
| ΔIC L | 0.25±0.34 | −0.03±0.38* | 0.10±0.53 | −0.28±0.47* | ||
| IRV L | 2.27±0.78 | 1.87±0.55 | 1.98±0.86 | 1.21±0.40** | 0.81±0.34 | 0.71±0.40 |
| EELV/TLC % | 48.2±8.6 | 55.9±9.3* | 43.6±8.7 | 56.8±5.8*** | 46.5±7.2 | 61.1±3.4*** |
| EILV/TLC % | 61.7±8.7 | 67.8±8.4 | 67.0±10.2 | 79.6±5.2*** | 86.3±5.3 | 87.9±6.4 |
| Work of breathing J·min−1 | 3±1 | 4±3* | 16±7 | 32±17** | 177±112 | 87±38** |
| EMGdi/EMGdi,max% | 7.8±4.3 | 12.8±3.4** | 17.9±11.7 | 37.3±17.3*** | 59.3±12.6 | 59.5±17.5 |
| (EMGdi/EMGdi,max)/(Pdi/Pdi,max) | 0.30±0.20 | 0.35±0.10 | 0.52±0.27 | 0.87±0.38** | 1.31±0.40 | 1.26±0.41 |
| Pes/Pes,max % | 8.4±4.0 | 10.5±3.3 | 14.6±5.0 | 23.3±7.7*** | 38.5±11.9 | 38.2±8.1 |
| VMR (ΔPg/ΔPes) | −1.26±1.01 | −1.62±1.28 | −0.34±0.64 | −0.14±0.58 | 0.00±0.48 | 0.13±0.88 |
Data are presented as mean±sd. HEWR: highest equivalent work rate; COPD: chronic obstructive pulmonary disease; V′O2: oxygen uptake; SaO2: arterial oxygen saturation; V′E: minute ventilation; VT: tidal volume; fR: respiratory frequency; V′CO2: carbon dioxide production; PETCO2: end-tidal carbon dioxide tension; IC: inspiratory capacity; ΔIC: change in IC from rest; IRV: inspiratory reserve volume; EELV: end-expiratory lung volume; TLC: total lung capacity; EILV: end-inspiratory lung volume; EMGdi: diaphragmatic electromyography; EMGdi,max: maximal EMGdi; Pdi: transdiaphragmatic pressure; Pdi,max: maximal Pdi; Pes: tidal oesophageal pressure; Pes,max: maximal Pes; VMR: ventilatory muscle recruitment; ΔPg: change in gastric pressure. *: p<0.05; **: p<0.01; ***: p<0.001.