The best fitness tool may be your beagle's leash, say Northwestern University docs. Dogs are great partners because they "never say no, never talk you into not exercising and never sabotage you," says researcher Robert F. Kushner, MD.
While people provide helpful input (cheerleading), we also bring negative influences (we're inconsistent). A pooch shows persistence by fussing until you walk, and he sees it as fun, not a chore. Plus, you feel parental pride when you walk your dog.