You can take your workout out of the gym and into the open air at Rokakoshunen Park. It's a great place to do some situps, crunches or a little yoga.
You'll soon discover why this Setagaya outdoor sports and fitness area is a hit with travelers. If you're searching for more to see and do here, Meiji Jingu Shrine, Shinjuku Gyoen National Garden, and Yoyogi Park are in this area as well. They won't take you very long to get to from Rokakoshunen Park.