Say you are in Tokyo and want to go for a jog but you have no gym subscriptions or you prefer outdoor running. Where to go? There are plenty of places, actually, where you can satisfy your fitness needs, without having to run through cars and wait at traffic lights.
The easiest place to go for a run is Yoyogi park, a mere short walk from JR Harajuku station. in addition to a huge area for pic-nics and various activities, there is a running track all around the park, I believe 3 km, that's just perfect for those who need a quick but satisfying run. I usually stay around only one side of the park when I go there with friends to spend the day, but one day I was taking a walk along the walking/running trail and I realized that there's so much more than just a fountain and a lake in that park! It's almost a sightseeing trail. The path is mostly in the shade, and that allows people to go running at any time, no matter how hot it is. In that park, temperatures are a few degrees lower than elsewhere in town. And, surprisingly, there aren't many people jogging at all times, so if you are looking for a peaceful place to run, go to this park.
Another famous running trail is the 5 km route around the Imperial Palace, in central Tokyo. The closest station for going there is JR Yurakucho station. Charity runs and other marathons and sports events are organized regularly there, so that place gets very busy. Year-round, a lot of passionate and professional runners use this trail, so it might not be as quiet as you may want. The positive side of it is that there are lockers and coin showers, so that you can bring your own gear, change and run, and later shower and you're ready to go.
Another park I came to know well is Komazawa Olympic Park, near Shibuya, reachable via Den-en-toshi line. I love this park. There are both running and cycling trails, well marked, color-coded and with distance marks, so that you can run along your lane and know how far you have gone. I always see a lot of people running in that park, at all hours. Probably the fact that people live near an "olympic" park pushes them to do sports? I wonder...
There are also indoor gyms and facilities, and I guess there is no need for subscription, but rather a pay-per-use fee, like in all city sports centers, so when bad weather surprises you, there is always a place to go and finish the training, while waiting for the bad weather to stop.
Anyhow, I have been several times to Komazawa park, often running together with the dog. And many other people do the same thing, or they ride their bikes and dogs follow. When I want to take a break I go to the fields area and watch kids playing soccer or basketball in the open court. Because there is also a baseball stadium in the park area, on weekends the park becomes busier for the games, so keep that in mind if you were hoping for a quiet Sunday exercise.
Finally, there's the Tama river. Many are the stations by this river, the major in Tokyo, and along its river banks people have enjoyed a lot of activities since the old days: golf, soccer, baseball, fishing, picnic areas, and of course biking and running. The great thing about running along this river is the length of the trail: it goes for something like 40 kms without interruptions. I was surprised myself when I learned this piece of information, because I only knew about the roughly 15 kms from Futako-Tamagawa station on the Oimachi and Denentoshi lines, all the way down towards the sea, which is the route I often cycle along. The path is way longer than that, it seems. Which is good news to the hard core runners who like training long distances, or marathons, for example. They may want to start the run all the way up from Fussa on the JR Ome line down to the end or vice-versa. The route goes more or less flat and parallel to the river course, on higher ground than the river itself, which I particularly like because allows me to watch all the many things that happen below. Be aware though that the path is not smooth, although paved, and is narrow, shared among cyclists, runners, oldies taking a stroll, and people just being around at any given time. Luckily, the trail splits at some points, and it is possible to choose a rougher surface, running at the same level of the water. Due to the dusty and gravely terrain, this latter one should be less beaten.
Photo: toshisyung on Flickr
I close with one fun fact about Tama river: it actually works as a separator between Tokyo and prefectures, such that the north bank is in Tokyo and the south bank is in Kanagawa. If you, then, pay attention to where the picnic areas are located, you'll find that they all are in the Kanagawa side, because on the other side of the river there is a BBQ ban...