Thursday, 1 December 2011

Olympic Countdown - Cycling

Are your eyes deceiving you? It’s not uncommon for researchers to give false information to their subjects to see what effect this can have, but it seems particularly prevalent when cyclists are being tested. In a recent experiment, Professor Kevin Thompson of Northumbria University used this idea to see if trained cyclists could go quicker than they ever had before over a 4,000m time trial. Using stationary bikes, the cyclists did two time trials to establish a baseline time. In the third and fourth trials, the cyclists raced against an avatar (a figure cycling) which they were told represented their baseline performance. In fact, this was only true for the third trial. On the fourth trial, the avatar was programmed with 2% more power, which correlates to 1% more speed. They found that the cyclists were up to 5 seconds faster than their baseline when racing against the accurate avatar, and up to 10 seconds faster when racing against the deception avatar. This suggests that we keep something in reserve even when we feel we’re going flat out. In another similar experiment, Dr Jo Corbett of Portsmouth University asked cyclists to race a 2,000m course as fast as possible in front of a computer screen showing an avatar of themselves doing the ride on a virtual course. On the fifth occasion they had to do this exercise they were told to race against another cyclist behind a screen whose avatar was also projected on to the same virtual course. In reality, however, they were actually racing against their own best time. On this fifth race, 12 out of the 14 participants were significantly faster in the fifth race, when they believed they were racing an opponent, even though they had been apparently completely exhausted in the other races. The difference was a final burst of speed which ensured their victory, and their average speed increased from 38.4km/h to 39km/h. It seems that competition allows athletes to dip into these hitherto untapped sources of energy. To test this idea, Professor Thompson repeated his experiment using two groups of cyclists. One group was told that they would be racing against an avatar that had either 2% or 5% more power, which meant either 1% or 2% quicker than their own best time. The other group was deceived. They were told that they were racing against an avatar that matched their best time, although in reality they were also racing an avatar that was either 1% or 2% quicker. The group that knew they were racing quicker avatars soon gave up trying to match the avatar’s speed, whether it was 1% or 2% quicker. The deceived group matched the avatar’s speed when it was 1% quicker. But 2% was too much, and they gave up about halfway through, and some ended up with a time that was worse than their best effort. And there are other ways of deceiving athletes that might eke out improved performances. Earlier this year, Dr Paul Castle and others from the University of Bedford engaged 7 cyclists in 30-minute stationary trials under three different conditions. In the control trial, the room temperature was set at 21.8°C (71.2°F). A second “hot” trial was held in a room at 31.4° (88.5°F). In the final trial, the temperature was displayed as 26.0°C (78.8°F), but was in reality 31.6°C (88.8°F), the hottest of the three. As expected, the cyclists performed worse in the hot trial (31.4°C) than in the control (4% less distance). But in the deception trial, they cycled slightly further in the time than they did in the control, even though they were actually cycling in temperatures marginally higher (31.6°) than in the hot trial. The researchers even found that the skin temperature of the participants was 0.5°C lower in the deception trial than in the hot trial. So, incorrect information from the conscious brain can lead to subconscious effects that can improve performance. But it also suggests that negative beliefs about conditions such as the weather will have a deleterious effect: if you think it’s going to be too hot or too cold to perform well, it probably will be. The final experiment looked to explain why cyclists doing, say, 40km, will generally lose speed towards the end, but will often do a really quick last 2,000m. This is when their muscles should be most tired. A team in South Africa led by Professor Tim Noakes told cyclists that they would do four 30-second trials, one 33-second trial and one 36-second trial. However, on some trials the clock was programmed to run more slowly, so they were actually doing two 30-second trials, two 33-second trials (one of which they thought was 30 seconds) and two 36-second trials (again, one of which they thought was 30 seconds. You might expect the cyclists to ride with more power initially on the deception 36-second trial compared with the informed 36-second trial. But in fact their power output was the same on both trials until the 33-second point, after which power fell significantly for the last three seconds of the deception trial. This shows again that information from the conscious brain can affect performance, this time in a negative way, overriding muscle fatigue. It seems that the subconscious brain pre-determines the amount of effort that will be required for the task. In the deception trial, it took three seconds before it realised that the expected duration had passed, and then it recalculated the intensity to a lower level for the remainder of the task by reducing the nervous stimulation to the muscles. This shows that the fatigue is largely caused by mental processes, i.e. a perception in the brain, sent from the subconscious to the conscious brain, rather than muscle fatigue. And this is why you can pick up speed towards the end of a 40km bike ride, when the conservative energy-saving policy of the subconscious brain can be overridden in the knowledge that there’s not much further to go, and a recalculation can take place. In fact the brain is constantly calculating and re-calculating the power output required (and therefore the pace) in response to the distance left to race and the cyclist’s physical state, which the brain is trying to protect. This also explains the benefits of interval training, which mixes high-intensity exercise with recovery breaks. It seems to work because you learn that going faster than you think you can doesn’t do any harm. And when you’re feeling fatigued towards the end of a race, this knowledge may also enable you to relax and keep going longer and faster than you would have thought possible. David Donner