General characteristics
| Characteristics | Total group (n=120) | HF-NMES (n=41) | LF-NMES (n=39) | Strength training (n=40) | p Value |
|---|---|---|---|---|---|
| Sex (M/F) | 62/58 | 24/17 | 19/20 | 19/21 | 0.555 |
| Age (years) | 64.8±0.8 | 64.4±1.3 | 66.2±1.3 | 64.0±1.3 | 0.440 |
| Pulmonary function | |||||
| FEV1 (L) | 0.85±0.03 | 0.87±0.04 | 0.87±0.07 | 0.80±0.05 | 0.578 |
| FEV1 (% predicted) | 33±1 | 33±2 | 35±2 | 33±2 | 0.645 |
| FEV1/VC max (%) | 32±1 | 31±1 | 31±2 | 33±2 | 0.545 |
| Tlco (% predicted) | 41±1 | 39±2 | 43±2 | 42±3 | 0.558 |
| LTOT (%) | 51 | 56 | 54 | 43 | 0.429 |
| GOLD classification (I/II/III/IV) | 0/12/36/72 | 0/5/12/24 | 0/2/14/23 | 0/5/10/25 | 0.942 |
| GOLD classification (new) (A/B/C/D) | 0/3/0/117 | 0/2/0/39 | 0/0/0/39 | 0/1/0/39 | 0.380 |
| BMI (kg/m2) | 24.8±0.5 | 24.1±0.8 | 25.5±0.8 | 24.9±0.8 | 0.441 |
| FFMI (kg/m2) | 16.5±0.2 | 16.3±0.3 | 16.6±0.3 | 16.6±0.4 | 0.688 |
| Isokinetic quadriceps muscle function | n=120 | n=41 | n=39 | n=40 | |
| Peak torque (Nm) | 76.2±2.4 | 78.7±4.4 | 76.1±4.1 | 73.4±4.1 | 0.682 |
| Peak torque (% predicted) | 54±1 | 54±3 | 55±2 | 53±3 | 0.812 |
| Total work (J) | 1175±44 | 1189±87 | 1164±67 | 1175±76 | 0.975 |
| 6-Min walk test | n=120 | n=41 | n=39 | n=40 | |
| 6MWD (m) | 322±8 | 311±16 | 315±14 | 337±14 | 0.412 |
| 6MWD (% predicted) | 52±1 | 48±3 | 52±3 | 54±3 | 0.204 |
| Cardiopulmonary exercise test | n=104 | n=35 | n=33 | n=36 | |
| Peak load (W) | 44±1 | 45±2 | 45±2 | 44±2 | 0.984 |
| Peak load (% predicted) | 40±2 | 33±3 | 44±3 | 44±5 | 0.083 |
| Peak VO2 (mL/min) | 820±21 | 831±37 | 829±43 | 806±30 | 0.858 |
| Peak VO2 (% predicted) | 58±5 | 46±5 | 57±6 | 68±11 | 0.179 |
| Peak VE (%MVV) | 94±4 | 91±6 | 93±6 | 97±7 | 0.790 |
| Peak HR (% predicted) | 75±1 | 74±1 | 75±3 | 75±1 | 0.830 |
| Constant work-rate cycling endurance test | n=96 | n=33 | n=30 | n=33 | |
| Cycle time (s) | 191±10 | 199±20 | 188±15 | 185±14 | 0.836 |
| Hospital Anxiety and Depression Scale | n=112 | n=39 | n=37 | n=36 | |
| Anxiety (points) | 8.9±0.4 | 7.3±0.7 | 9.7±0.7 | 9.8±0.6 | 0.018 |
| Depression (points) | 8.4±0.4 | 8.1±0.5 | 8.0±0.7 | 9.1±0.7 | 0.436 |
| St George's Respiratory Questionnaire | n=109 | n=38 | n=36 | n=35 | |
| Symptoms (points) | 66.3±1.6 | 66.9±2.5 | 67.0±2.9 | 65.0±3.1 | 0.850 |
| Activity (points) | 81.7±1.6 | 84.4±2.2 | 80.9±3.0 | 79.6±2.9 | 0.431 |
| Impact (points) | 53.1±1.7 | 50.8±2.4 | 52.8±3.4 | 55.9±3.0 | 0.462 |
| Total score (points) | 63.9±1.3 | 63.6±1.7 | 63.7±2.6 | 64.6±2.3 | 0.932 |
Values are expressed as mean±SEM.
Cycle tests were not performed by all subjects; major reasons were unstable blood gases or a severely disabled condition.
The major reasons for not performing questionnaires were technical problems.
Please see online supplementary data repository tables E3 and E4 for more details.
BMI, body mass index; FEV1, forced expiratory volume in one second; FFMI, fat free mass index; GOLD, Global initiative for chronic Obstructive Lung Disease; HF-NMES, high-frequency transcutaneous neuromuscular electrical stimulation; HR, heart rate; LF-NMES, low-frequency transcutaneous neuromuscular electrical stimulation; LTOT, long-term oxygen therapy; Tlco, carbon monoxide transfer factor; VC max, maximum vital capacity; VE, minute ventilation; VO2, oxygen uptake; MVV, maximal voluntary ventilation; 6MWD, 6-min walk distance.