Barring significant medical illness such as prior heart attacks, serious coronary artery disease, stroke, such and such, there s no reason why a healthy 75 year old female can t undergo a treadmill test. Even with some blood pressure and heart disease the treadmill test is still fairly safe to undergo. Reasons why you would not want to undergo include, easy fatiguabilty with risk of falling down from dizziness or vertigo, or experiencing shortness of breath or chest pain during very minimal exercise. An alternative to a treadmill test is a medical stimulation test which simulates physical activity on the heart by injecting a medication such as dobutamine. This is the preferred method of a stress test for those who cannot tolerate physical activity for whatever reason.