Intervention group: active NMES (350 μs pulses - 50 Hz frequency) will be applied at the lower third of the thigh, just above the patella, and the proximal electrode 5-10 cm below the anterior superior iliac spine for quadriceps muscle stimulation, and for intercostal muscles stimulation, NMES will be bilaterally, parallel to the ribs, in the intercostal space. The proximal electrode will be positioned close to the sternum, and the distal electrode laterally, close to the midaxillary line. In addition to conventional pulmonary rehabilitation program that comprised diaphragmatic and pursed lips breathing.
control group: placebo NMES at the same points in addition to the same conventional pulmonary rehabilitation program
