Mine would be an hour and 1/2 of old timers ice hockey on a weekly basis. It is aerobic and considered excellent for maintenance of your cognitive faculties. Old timers hockey does not permit hitting and is quite safe to play. In Dr. John Medina's recent New York Best Seller titled Brain Rules one can find an argument for ice hockey being the ideal activity to increase the BDNF to your brain; thus, enhancing your intellect. However, one could argue most significantly, hockey allows for the externalization/exercising out of your aggressions. Thus, resulting in peacefulness once again.