This study will examine the acute effects of high intensity interval ergometry on peripheral concentrations of lactate and hydrogen ions, as well as cognitive function. Approximately 60 healthy, college-aged males will participate in the Wisconsin Card Sorting Task (WCST), a measure of executive function, two times over a span of two weeks. Prior to the WCST, participants will complete either a warm-up, a warm-up and high intensity interval exercise, or a stationary period. Changes in lactate, pH, and WCST score will be evaluated between and within groups in relation to the presence of the high intensity exercise stimulus.