These Exercises Burn the br Most Calories, According to Science According to Dr. Tim Church, br an exercise researcher at Louisiana State University, the more muscles you engage and the harder (and longer) you work those muscles, the more energy your body will use. Dr. Tim Church, via 'Time' High-intensity interval br training (HIIT) can burn br a significant amount of calories br in a short period of time. If you are short on time, HIIT is br probably your best option, but many people aren't br willing or able to engage br in high-intensity training. John Porcari, professor at the University of Wisconsin, says a "more fair" exercise assessment results when people go at a comfortable pace. John Porcari, via 'Time' Ultimately, the best workout for br burning calories is "the one you br actually do," according to Church. Depending on the time you have,br as well as your physical ability, both HIIT and running br seem to offer desirable results.