Graded exercise testing (GXT) is the most widely used assessment to examine the dynamic relationship between exercise and integrated physiological systems. The GXT is a diagnostic test used to rule out coronary artery disease and/or abnormal rhythms and to evaluate exercise capacity. This test allows doctors to observe the ability of their patients to perform cardiovascular exercise (functional capacity), detect any evidence for lack of blood supply. Learn more from WebMD about stress tests and how they're used to. An exercise stress test, also known as a graded exercise test (GXT), provides important information on the patient beginning an exercise-training program. Graded exercise tolerance tests (GXT), whether with or without imaging require exercise on a treadmill to achieve the patient's target heart rate,.