Effects of Chemoradiation and Surgery on Cardiopulmonary Fitness and Tumor Neoplastic Phenotype in Gastrointestinal Malignancies

All subjects will undergo a maximal cardiopulmonary exercise test and resting metabolic rate study. Prior to the exercise treadmill test, each subject will have a resting ECG and blood pressure to determine whether there are any abnormalities that would contraindicate exercise testing.This exercise test involves exercising on a treadmill to maximal exertion, during which the subject's breathing and oxygen consumption are measured. The subject will wear nose clips to prevent exhaling air through their nose and a mouth piece that will allow all exhaled air to be analyzed through the metabolic cart. The subject's electrocardiogram (ECG), blood pressure, and perceived exertion are monitored throughout the test by trained personnel.