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The electric bike setting the pace in Rio explained

Cyclists compete in the Women's Keirin first round at the Rio Olympic Velodrome during the 2016 Summer Olympics in Rio de Janeiro, Brazil, Saturday, Aug. 13, 2016. (AP Photo/Patrick Semansky)

Cyclists compete in the Women's Keirin first round at the Rio Olympic Velodrome during the 2016 Summer Olympics in Rio de Janeiro, Brazil, Saturday, Aug. 13, 2016. (AP Photo/Patrick Semansky)

“Doped” bikes — bicycles that get an illegal boost from hidden electric motors — have become a plague in two-wheel racing in recent years.

So why is there a rider in the Olympic velodrome who isn’t pedaling at all?

If you’ve been watching the track cycling at the Olympic Games in Rio, you may have noticed an oddly upright fellow leading the field for the first few laps of the keirin, a high-speed bicycle race that became popular in Japan as a gambling sport after World War II and was added to the Olympic Games in 2000.

The rider’s job is to set the pace and act as a wind-blocker, bringing the competitors up to 31 mph in the first five and a half laps of the eight-lap event. The motorized bike he’s riding is called a derny, which pulls off the track and leaves the athletes to sprint toward the finish.

Forcing the cyclists to a high starting speed creates an exciting spectacle: The racers often crack 50 mph — and sometimes a few bones — during the sprint, as NASCAR-like crashes on the high-banked tracks are common.

Dernies have evolved over the years. Gasoline-powered motorcycle or moped-style versions were originally used, but they were replaced this time around by an all-electric scooter with no pedals.

Built by a German company called Elmoto, the new derny can hit 37 mph and features a precise accelerator and digital speedometer to help the rider set the perfect pace. Its 1.5 kilowatt-hour battery pack offers a range of up to 40 miles between charges, which should be plenty for a day of competition, since it travels less than a mile per race.

It goes for around $4,000. That sounds like a lot, but it’s a bargain compared to the racing bikes that follow it. They’re worth upwards of $25,000 each.