J. Mark VanNess, PhD, is a cardiovascular biologist and Distinguished Professor in the department of Health and Exercise Science at the University of the Pacific. He studied biology, chemistry, and exercise science as an undergraduate student and exercise physiology for his master’s degree. He received his doctoral degree from the program in Neuroscience at Florida State University. He has postdoctoral training from the University of Texas Health Science Center in San Antonio in Pharmacology and Physiology, and presently teaches at the University of the Pacific. His primary research interest focuses on ME/CFS and the cardiovascular and metabolic abnormalities that are unmasked by exercise testing in the illness. His collaboration with the Workwell Foundation has helped in the identification and description of post-exertional malaise in ME/CFS. Objective evidence documenting illness severity helps with treatment and efficacy for interventions.