HEROICS will be performed this July. The lasts 21 days, covers 3600 kilometres and includes 25 lung-busting climbs in the Alps and Pyrenees. Each extraordinary performance in the race will, however, generate suspicion as well as admiration. Allegations of doping have plagued the Tour for so long that any rider who excels now inevitably attracts talk of drug use.
But what if a superhuman performance itself could be used as evidence of doping? That鈥檚 the thinking behind a new strategy, which asks: 鈥淚s this physiologically possible without the aid of drugs?鈥�
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The idea is straightforward: work out the boundaries of human ability, based on what we know about physiology and its maximal capabilities. If an athlete鈥檚 performance lies outside this limit, they are highlighted as a potential drug-taker and given more frequent and extensive drug screenings.
鈥淚f an athlete鈥檚 performance lies outside 鈥榥atural鈥� limits, they are highlighted as a potential drug-taker鈥�
The strategy has the backing of many sports physiologists. The French government is considering using it in sporting events, and the World Anti-Doping Agency (WADA) is running pilot studies. But there is a fundamental difficulty: elite sport is all about extraordinary abilities. Can we really distinguish between exceptional athletes and their chemically enhanced rivals on the basis of performance?
A key measurement that could be used to investigate its potential is a cyclist鈥檚 power output. This is a measure of the energy a rider uses to drive the bike up a hill (see diagram). One popular drug, the hormone erythropoietin (EPO), has been shown to increase the peak power output of healthy volunteers by 16 per cent after four weeks of taking the drug. It also increased the 鈥渢ime-to-exhaustion鈥�, the duration over which a subject could maintain a high pace, by over 50 per cent (European Journal of Applied Physiology, ).FIG-mg27673902.jpg
Several successful Tour de France riders, including Bjarne Riis, the 1996 winner, have admitted to using EPO in the mid to late 1990s. Prior to widespread EPO use, Tour winners鈥� average power output was 380 watts on big climbs, with none exceeding 410 W, says Antoine Vayer, a professional cycling coach based in Pordic, France. Riis had an average power output of 445 W on Tour climbs in 1996. From 1994 onwards, Vayer calculated that around six riders per year averaged over 410 W. Levels dropped at the end of the decade as , in urine or blood samples, became more accurate.
Something else that could raise suspicions about a cyclist is a high VO2 max 鈥� a measure of the maximum rate at which a person uses oxygen.
The highest VO2 max figures on record 鈥� around 90 millilitres of oxygen per kilogram per minute 鈥� come from cross-country skiers and rowers, who use a high proportion of the muscles in their bodies. Elite cyclists generally score lower because their activity uses a smaller muscle mass.
In one study of 11 world-class cyclists, the highest VO2 max was 82.5 ml/kg/min (). Levels above 85 ml/kg/min are 鈥渧ery rare鈥�, says Ross Tucker at the University of Cape Town in South Africa. Olaf Schumacher at the University of Freiburg in Germany agrees, saying that values above this for cyclists are 鈥渄efinitely very high鈥� and beyond what he feels is 鈥渘atural鈥�.
At the request of 麻豆传媒, Tucker used Vayer鈥檚 power output data to estimate the VO2 max of several riders on the climb of Alpe d鈥橦uez 鈥� one of the longest and steepest on the route 鈥� over a number of years. Assumptions made in the calculation, such as a rider鈥檚 efficiency in converting energy into moving the bike, limit its accuracy, but on the last eight occasions on which the Tour has visited Alpe d鈥橦uez, Tucker estimates that a number of the riders had a VO2 max above 85 ml/kg/min, with some over 90 ml/kg/min (see graph).
Do these high levels reflect a leap in human achievement, or are they a signature of artificially enhanced physiology? Power outputs have risen once more since the dip in 2000 and although several riders have had positive drug tests, there are several with VO2 max levels above 85 ml/kg/min who have a clean record. Tucker estimates that Lance Armstrong, the US rider who has won a record seven Tours, would have produced a VO2 max of between 88 and 97 ml/kg/min when he climbed Alpe d鈥橦uez in 2004. Armstrong has not been found to have used performance-enhancing drugs, which demonstrates the strategy鈥檚 limitations.
On the basis of a person鈥檚 physiological measurements alone, it is impossible to say otherwise. 鈥淒oping can never be inferred from performance only,鈥� says Schumacher.
Nevertheless, Schumacher and others say that these kinds of sophisticated physiological analyses could aid doping authorities. Professional cyclists are already subject to regular blood and urine tests during and outside of races. The results are added to their 鈥渂iological passport鈥� 鈥� a regularly updated record of each athlete鈥檚 test results. Periodic estimates of power output and VO2 max could be added to this.
Pierre Sallet, a physiologist and athletics coach in Lyon, France, has studied this approach for WADA. When analysing one climb in the Tour, Sallet observed a rider who produced an average power in excess of 480 W for more than 30 minutes, a level which he considers 鈥渂eyond all norms鈥� and reason to investigate further.
WADA plans to introduce steroid and hormone data to its biological passport scheme this year, and says that physiological performance data could follow. Fred Grappe of the University of Franche-Comt茅 in Besan莽on, France, is meeting with officials from the French Ministry of Health and Sports in August to discuss a possible nationwide performance monitoring programme. Grappe says he would like to use a combination of lab tests and race monitoring to track performance.
Knowledge of what is considered to be humanly possible may not be enough on its own, but in parallel with drug tests, physiological monitoring can give authorities 鈥渁 good idea of those who are not so clearly clean鈥�, says Fabio Manfredini at the University of Ferrara in Italy, who is integrating performance data into biathlons this year. 鈥淭hen we can try and control them.鈥�
