At Tokyo's Fuwaku rugby club, the dozens of players running, passing, mauling, scrummaging and crashing into one another in the shadow of the Aquatics Centre being built for the 2020 Olympics are unremarkable in all but one thing -- their age.

Fuwaku, founded in 1948, is one of approximately 150 Japanese clubs that stage competitive, full-contact matches for players over the age of 40.

The oldest man on the park is sprightly 86-year-old lock forward Ryuichi Nagayama.

As in rugby clubs around the world, the attraction is only partly the love of playing the game.

In a country where there is much concern over the loneliness of the elderly, rugby not only keeps the players active but also offers a ready-made social life.

"You tackle and battle each other, but the gathering after the play is so enjoyable and fun," said Nagayama, who is the oldest active player but junior to three club members in their 90s.

As a doctor, Nagayama is well aware of the risks involved of playing a high impact sport at his age and the club's website gives detailed advice on health precautions and even links to a life insurance company.

Fuwaku's General Manager Mitsuaki Okajima estimates there are over 10,000 veteran rugby players currently playing at clubs across Japan and his club alone has 300 players competing across all age categories.