The trained bicyclists thought they had ridden as fast as they possibly could. But Kevin Thompson, head of sport and exercise science at Northumbrian University in England, wondered if they go could even faster.

So, in an unusual experiment, he tricked them.

In their laboratory, Dr. Thompson and his assistant Mark Stone had had the cyclists pedal as hard as they could on a stationary bicycle for the equivalent of 4,000 meters, about 2.5 miles. After they had done this on several occasions, the cyclists thought they knew what their limits were.

Then Dr. Thompson asked the cyclists to race against an avatar, a figure of a cyclist on a computer screen in front them. Each rider was shown two avatars. One was himself, moving along a virtual course at the rate he was actually pedaling the stationary bicycle. The other figure was moving at the pace of the cyclist’s own best effort — or so the cyclists were told.

In fact, the second avatar was programmed to ride faster than the cyclist ever had — using 2 percent more power, which translates into a 1 percent increase in speed.