The study aims to determine the difference in maximal oxygen consumption between high intensity interval training (HIIT) and aerobic exercise among recreationally active adults aged 20-30 enrolled in a fitness center in Davao City, Philippines. Participants completed baseline testing and two weeks of either HIIT or aerobic exercise, separated by a one week washout period, before completing final testing. The results and analysis will provide insight into which training method is more effective for improving cardiovascular fitness.