Research suggests high-output, bodyweight-based exercises such as plyometrics yield awesome fitness gains in very short workout durations . Since there’s no equipment involved, bodyweight workouts make it easy to transition quickly from one exercise to the next. Shorter rest times mean it’s easy to quickly boost heart rate and burn some serious calories. The "core" is more than just abs. In fact, at least twenty-nine muscles make up the human core, and many simple bodyweight movements can be used to engage all of them. Such exercises improve core strength for better posture and improved athletic performance .