This is a multi-center prospective follow-up study.

• to choose the stable COPD patients in community
• to compare different modes of exercise (cycling and walking)
• to compare the effect of different exercises on the quality of life,exercise endurance,dyspnea and depression

This is a multi-center prospective follow-up study.More than 20 hospitals participate the research. More than 300 stable COPD patients will be recruited.It is a two-year study. There are four groups, cycling and walking group(C-WG),cycling and non-walking group(C-nonWG),walking and walking group(W-WG),walking and non-walking group(W-nonWG).

1. All patients from four groups will finish baseline investigation and blood sample, including informed consent,questionaires(SGRQ,CRDQ,MRCQ,Depression Scale,etc.),spirometry,6MWT,MIP,MEP,BMI,CRP,TNF,IL-8, etc.Patients in C-WG and C-nonWG will finish cardiopulmonary test.
2. Patients receive 8 weeks training program, includes upper and lower extremities endurance exercises and respiratory muscle endurance exercises. Patients in both CGs cycling at cycle ergometry. Patients in W-WG and W-nonWG walking instead. All patients receive training program twice per year, for two years. Patients were supervised by physicians or nurses at hospital while they are training.
3. In the non-training period, patients in W-WG and C-WG will continue to walk at community, supervised by nurses who call them every month. The other two groups(C-nonWG and W-nonWG) do not receive special requirement on exercise.
4. Telephone call interview will give to patients every month to find whether they have acute exacerbation. Patients are asked to record their activities during daytime in the diary cards.
5. All patients will finish investigation and blood sample after one year and two year,including questionaires,spirometry,6MWT,MIP,MEP,BMI,CRP,TNF,IL-8, etc.Patients in CG will finish cardiopulmonary test.

Inclusion Criteria:

• according to GOLD, patients who are diagnosed as COPD, lung function at II or III grades (II:50%≤FEV1<60%pre；III:30%≤FEV1<50%pre）；
• 40≤age≤75 years old；
• don't have acute exacerbation in the past one month；
• SpO2 > 88% at rest；

Exclusion Criteria:

• diabetes,blood glucose don't control well;
• vascular diseases(vasculitis,deep venous thrombosis,varicose veins, etc);
• joint diseases which may affect activities;
• cerebrovascular diseases which may affect activities;
• unstable angina during the past 1 month of acute myocardial infarction in the past 6 months;
• severe arrhythmia;
• cardia insufficiency;
• hypertension which don't control well(systolic pressure>160mmHg and/or diastolic pressure> 100mmHg);
• chronic liver or renal insufficiency;
• cognitive handicap.