I did have a stress test and it was no big deal. They have you do some specific breathing exercises to test your lung function and an EKG to test your heart function. They test you at rest and at stress. The stress can be produced chemically or physically on a treadmill or a bike. The idea is to see how well your lungs carry oxygen and clear co2 and if you have and blockage throughout your heart vessels. Is very important for those who are obese and have other medical issues like hypertension, high cholesterol, or diabetes. I was very glad to have mine done. I have had this fear for some time that I would have a heart attack early in life. Seeing it in paper that my heart is functioning well is a relief. I know I haven't exercised it enough in life to make it a strong muscle.