They said they will encourage him to focus on aerobics for the next few weeks and not engage in vigorous upper-body exercise until his chest area around the device has healed.

CNN: Cheney returns to work after implant

Dr. GERBER: You're probably going to want to make that investment in a patient that truly has something to gain, and those would be the patients who already have signs or symptoms of heart (unintelligible) disease: Such as chest pain, or shortness of breath or exercise intolerance.

NPR: Study: Heart CT Scans May Pose Risk

In heart disease studies, for example, subjective outcomes might include the duration and severity of chest pain, shortness of breath, or ability to exercise without pain.

FORBES: Clinical Trial Advice For Investors From Two Pros