"This is my Tour de France," says van Velthooven, as he warms down post-race. "It is as big as it gets in keirin racing. It can be a strange existence but it has probably been the making of me, though you have your ups and downs."
This week hasn't been great. After being tactically out-thought in his semifinal, he finished last, relegating him to the C final today. We are at the velodrome in Ichinomiya (population 330,000) just outside Nagoya, three hours east of Tokyo by bullet train. Like many here, it has a huge glass fronted grandstand overlooking the finish line and terraced seating encircling the track.
The riders (99 at this event) arrived four days earlier and immediately went into lock down. All communication devices are surrendered while riders are locked away in the velodrome. No outside contact is permitted. They sleep four to a dormitory, and shower and eat together. Lights go out at 10pm. During the day, riders pass the time in the waiting room, each on his own mat.
Clothes hang from lines stretched across the room and there are neat piles of comics and magazines on the floor.
The isolation is deemed necessary to protect the integrity of the sport. Gambling is technically illegal in Japan (there are no casinos) and keirin is the only Japanese sport officially licensed for gambling.
Watching the action, it occurs that these men are the closest we have to human racehorses. The nine riders in each race wear brightly coloured uniforms, the numbers prominent on back and chest. Combined with heavy padding and huge helmets, they can resemble cartoon characters.
Detailed programmes list form and preferred tactics, while punters are told which gear each competitor will be using. Riders parade an hour before each race. There is no contact with the fans, though the pressure is apparent if riders don't perform to ranking in a high stakes race. Because of its gambling connections, keirin is often linked with the Yakuza, the Japanese mafia.
"It is always a little unnerving when you see a fan waving you on and he is missing half his little finger," says van Velthooven, referring to the Yakuza custom of lopping off the top of a finger as atonement for a mistake, "though that hasn't happened very often".
Van Velthooven's final goes well. On the last lap, he escapes the attention of a portly opponent who tried to shove him to the outside of the track (intentional contact is permitted) and hangs on to win by a nose.
The sport is hugely physical. Bikes are made from steel, (no carbon fibre here), spoked rather than disc wheels and toe straps standardised according to regulations first set down in 1957. The velodromes are mostly outdoors on concrete and races are staged even in the rain.
"We are like working dogs for the daily punters," laughs van Velthooven. "Being here makes you pretty tough, mentally and physically, because you are always racing."
Says fellow foreigner Jason Niblett: "It's basically gym work on a bike. The bikes are heavy and there is the wind factor. When you go back to being indoor with a light bike, you feel so strong; you just need to get your speed back."
NIBLETT, AN Australian who won gold at the 2010 Commonwealth Games, is well placed in his final, until he is expertly smashed off his racing line by a rival, sending him up the banked track and way out of contention. The contact is a dangerous ploy, as riders hit 70km/h on the home straight, and crashes are unforgiving on the tarseal, but it makes for a thrilling spectacle.
Some of the racers, whose main role is to block, wear thick body armour covering their shoulders, chest and arms under their lycra tops and even knuckle plates in their gloves while stretchers at each corner are a reminder of the dangers.
Crashes can be painful - and costly. Van Velthooven estimates one fall in 2010 cost him $10,000 in lost prize money. Living in such close proximity with rivals could invite tension but Japanese custom tries to minimise this.
"If there is a crash, the rider will come to you after the race to apologise," says Niblett. "The culture mandates that you accept that apology, though once I was so angry, I refused. I'm not sure if that got through the translation."
Keirin can be a 30-year career, with most racing well into their late 40s (the oldest current rider is 60). While some foreigners thrive, others barely survive.
"It can be mentally tough," says van Velthooven. "Adapting to the culture, the language, the isolation and the constant travel. It's also very tactical - so you might find yourself losing to a 40-year-old, which is pretty hard to take. Some never adapt; one recent import, who was a star on the world scene, barely made a mark in Japan."
Van Velthooven's Japanese odyssey can be traced back to a conversation round the kitchen table just over four years ago.
"I was with my dad and my manager and they asked me where I wanted to go in the sport," says van Velthooven. "Racing keirin here was always a dream but I knew I would have to do well at world championships and Olympics to get noticed and invited. Things have happened a bit quicker than expected."
The 24-year-old arrives home a few days before Christmas but it won't be a quiet time. After inviting the whole country to his belated 21st in the wake of his Olympic jubilation, around 500 people are expected to descend on his parents' farm between Feilding and Palmerston North. Moa have supplied a pallet of beer and friends from a local gym will provide security.
"It's been a long year so I'm looking forward to a couple of quiet drinks," says van Velthooven, "though I'm not sure if there's much chance of that." Michael Burgess travelled to Japan with the assistance of the Asia New Zealand Foundation.
