REVOLUTION ON THE OUTSIDE, EVOLUTION ON THE INSIDE. Beat Theory Fitness is a fitness franchise headquartered in the UK. We offer group personal training workouts based on high intensity interval training (HIIT) that blend cardiovascular and strength training from our very own studio-gym facilities. Our UNIQUE heart-rate-monitored group interval fitness concept is designed to stimulate metabolism, increase energy, and provide group support and accountability. The desired result of the training regimen consists of more energy, visible and lasting toning, and extra calorie burn for up to 36 hours after a workout.