The aim of this study is to demonstrate the effectiveness of combined concentric and eccentric aerobic training in subjects with COPD, in terms of strength, lung capacity, functionality, and short-term health quality. A randomized, examiner-blinded clinical trial has been designed for this purpose, following the CONSORT guidelines for clinical trials and the ethical principles of the Declaration of Helsinki. A total sample of 40 subjects has been estimated. The study is aimed at patients diagnosed with mild or moderate COPD. A program of 12 group sessions will be conducted over 4 weeks. Each session will last 75 minutes and will include strength exercises and respiratory physiotherapy, common to all subjects. The interval aerobic training will depend on the assigned group: treadmill with negative and positive (or neutral) incline (experimental group), treadmill with positive incline and/or cycle ergometer (control group). The following variables will be measured on the first and last day of treatment, as well as one month after the intervention ends: thickness, cross-sectional area, and ultrasound intensity of the rectus femoris muscle; diaphragmatic excursion and thickness; 5 sit to stand test; get up and go test; Borg scale; maximum respiratory pressures; grip strength in both hands and maximum quadriceps strength; spirometric assessment of FEV1 and SF-12 health quality questionnaire.