Neder 2002.

Methods	Randomised controlled trial
Participants	15 medically stable participants (9 men) were enrolled. 9 were allocated to the intervention group (mean FEV1 % predicted = 38 (SD 10) %, mean age = 67 (SD 8) yr). 6 were allocated to the control group (mean FEV1 % predicted = 40 (SD 13) %, mean age = 65 (SD 5) yr)
Interventions	Intervention: electrical stimulation of both quadriceps using a symmetric, biphasic square‐pulsed wave at a frequency of 50 Hz. Duty cycle was 2 s on, 18 s off for the first week, then 5 s on, 25 s off for the second week and then 10 s on 30 s off for the rest of the training period. The pulse width was 300‐400 µs and the intensity was titrated the maximum tolerable. Training was applied for 15 minutes (to each leg) in the first week and increased to 30 minutes thereafter, for 5 days per week for 6 weeks. The first week of training was supervised (in an outpatient department) and thereafter, training was undertaken at home with weekly visits by the therapist. Control: no stimulation
Outcomes	HRQoL via the CRDQ Fat‐free mass via bioimpedance (descriptive data only) Airflow obstruction via spirometry (descriptive data only) Lung volumes via nitrogen washout and single breath diffusing capacity for carbon monoxide (descriptive data only) Exercise capacity via a cardiopulmonary exercise test Quadriceps strength measured as torque and force during a maximum isokinetic contraction using an isokinetic dynamometer Quadriceps endurance measured using an isokinetic dynamometer
Notes	Investigator supported by a long‐term ERS fellowship
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "This was a prospective randomised controlled study." Details pertaining to the development of the randomisation sequence were not reported.
Allocation concealment (selection bias)	Unclear risk	No details given
Blinding of participants and personnel (performance bias) All outcomes	High risk	No mention of any attempt to blind participants or personnel. Control group did not receive any sham intervention. Unlikely that the investigators administering the NMES were blinded to group allocation.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No mention of blinding for outcome assessors. A lack of blinding of may have affected outcomes such as muscle strength, muscle endurance, exercise capacity and HRQoL.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Insufficient details on attrition to comment on whether this was a source of bias.
Selective reporting (reporting bias)	Unclear risk	No protocol available
Other bias	Low risk	Study appeared free from other sources of bias.