Participants A prospective study will be performed within the Cardiovascular Ward of Chang Gung Memorial Hospital, Linkuo. The inclusion criteria is diagnosed CAD and scheduled to receive elective CABG. Patients awaiting first-time elective CABG will be invited to participate in the study, and enrolled after giving written informed consent. Sixty patients will be enrolled. Exclusion criteria are musculoskeletal or neurological impairment precluding performance of cycling and walking assessment, atrial fibrillation, receiving anticoagulation therapy, inability to complete questionnaires, planned concomitant surgery, and a clinical status which requires emergent CABG. Additional 20 non-sedentary, age-matched healthy subjects without cardiovascular illness will be recruited as the control group. Non-sedentary life style is defined as walking more than 25 minutes in average per day according to the National Population Health Surveys of Canada. [14]