Mind over muscle

Then 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 per cent more power,which translates into a 1 per cent increase in speed.

Told to race against what they thought was their own best time,the cyclists ended up matching their avatars on their virtual rides,going significantly faster than they ever had gone before. While a 2 per cent increase in power might seem small,it is enough to make a big difference in a competitive event that lasts four to five minutes,like cycling for 4,000 metres. At the elite level in sports,a 1 per cent increase in speed can determine whether an athlete places in a race or comes in somewhere farther back in the pack.

The improved times observed in his experiment give rise to some perplexing questions. What limits how fast a person can run or swim or cycle or row? Is it just the body—do fatigued muscles just give out at a certain point? Or is the limit set by a mysterious “central governor” in the brain,as Timothy Noakes,professor of exercise and sports science at the University of Cape Town in South Africa,has called it,that determines pacing and effort and,ultimately,performance?

Until recently,exercise physiologists have mostly focused on the muscles,hearts and lungs of athletes,asking whether fatigue comes because the body has reached its limit. But athletes themselves have long insisted that mental factors are paramount.

Jo Corbett,a senior lecturer in applied exercise physiology at the University of Portsmouth in England,wondered how much competition can affect an athlete’s speed. To find out,he asked cyclists to ride as hard and as fast as they could on a stationary bicycle for the equivalent of 2,000 metres. As he rode,each rider was shown an onscreen figure representing the cyclist riding the course.

Then Corbett and his colleagues told each athlete that he would be racing against another rider hidden behind a screen. The researchers projected two figures on the screen,one the outline of the rider and the other the outline of the competitor. In fact,the competitor on the screen was a computer-generated image of the athlete himself in his own best attempt to ride those 2,000 metres. The cyclists rode furiously through the on-screen race. And,as happened in Thompson’s experiments,the cyclists beat their best times,finishing with a burst of speed that carried them to virtual victory by a significant length.

Corbett said the extra effort,above and beyond what the athletes had previously demonstrated,seems to come from the anaerobic energy system,one that is limited by the amount of fuel stored in muscle. The brain appears to conserve the body’s limited fuel to a certain degree,not allowing athletes to work too hard. But in a race,he said,the brain seems to allow athletes to tap more deeply into energy stores than would ordinarily be permitted. Still,there must be a limit to how fast an athlete can go,even with the most intense competition or even with deception. In a new study,Thompson tried to find what that limit is.

He used the same method as before: Cyclists on stationary bikes raced an onscreen avatar going a bit faster than the cyclist’s own best time. In one group,the only variable was competition. Cyclists were told that the avatar would be going 2 per cent faster or 5 per cent faster than the cyclist had ever gone. The other group was deceived. Each cyclist was told to compete against an avatar that would be moving as fast as that athlete had in his best effort. Actually,the avatar was programmed to race 2 per cent harder or 5 per cent harder.

The cyclists in the first group gave up from the start when they knew the avatar would be moving faster than they ever had—even when the avatars were going 2 per cent harder than the cyclists’ own best times. Instead,the athletes matched their own best efforts. Cyclists in the second group,who were deceived,kept up with their avatars when they were programmed to perform 2 per cent harder than each athlete at his best. But 5 per cent was just too much: The athletes kept up for about half the race,then gave up.GINA KOLATA