Your brain is a muscle, but new studies are revealing that certain types of exercise build it better than others. A recent study funded by the Academy of Finland examined how different kinds of exercise affect production of a protein called Brain-Derived Neurotrophic Factor (BDNF), which is responsible for triggering neurogenesis (the production of new neurons throughout life, which in turn determines how gracefully our brains age from a functional standpoint). The study was performed on a group of rats (the majority of neuroscientists believe animal subjects accurately reflect neurogenetic properties in human subjects) over seven weeks. Based upon this study, scientists concluded that steady cardio is the most neurogenetic form of exercise. High intensity interval training caused some neurogenesis, but was less effective than steady cardio, likely due to the additional stress on the brain according to the Finnish scientists. Weight training came in last, catalyzing the least neurogenesis. The moral of the story: muscles and neurons may be mutually exclusive outcomes when it comes to exercise.