When Helen Jenkins suffered a severe Achilles tendon injury in 2006, the now-reigning triathlon World Champion was warned that her sporting career was over. But the determined Welsh athlete defied the doomsayers to return to fighting fit form, winning her first World Championship in Vancouver in 2008. She is now one of Britain's best hopes of winning Olympic gold at this year's Games.
She has been helped by her coach, husband and fellow triathlete Marc Jenkins, but Helen also has a secret weapon: science. She has been undertaking "neurobics" brain training, where she eats, trains and even sleeps with less oxygen so that when she encounters the oxygen-rich air of London she is guaranteed to produce a turbocharged Olympic performance.
Helen is one of several Olympic athletes training under the guidance of Professor Damian Bailey, himself a former international athlete and head of the Neurovascular Research Laboratory at the University of Glamorgan, whose research has demonstrated that "exercise starts and ends in the brain".
"I know what it's like competing at the top end, having represented my country in football and athletics," he says. "But my brain wanted to take me places that my body couldn't follow: lots of pain without much gain. I simply had to find out why, and so turned to science for answers."
Bailey's research has challenged traditional dogma that performance limits are set by the heart, lungs and muscles.
"The advent of sophisticated magnetic resonance imaging and ultrasound techniques has provided us with a window into the brain and helped unlock some of the unsolved mysteries that set the limits of human performance," he says.
"We have come to realise that the most successful endurance performers are those who can best conserve the biggest amount of oxygen in their brains during exercise."
Bailey and his team turned to alternative superhuman models to test this theory, focusing on how high-altitude mountaineers and free divers overcame extremes of exercise and lack of oxygen that would usually be considered "incompatible with ordinary human life". This provided unique insights into how the brain "senses" oxygen and the defence mechanisms it deploys to optimise function. "The human brain is so oxygen-hungry that it soaks up a disproportionate 30 per cent of our body's energy budget," Bailey says.
"We can put our brains under extra pressure with intermittent bouts of exercise, combined with a lack of oxygen - a so-called high-altitude double whammy. This causes the brain to release tiny molecules known as free radicals.
"But rather than damage the body's cells, as was previously thought, they act like molecular on-off switches, which trigger the complex machinery required to get oxygen into our brains and keep it there. Over time our bodies adapt to their controlled release, boosting the training response and optimising oxygen delivery and performance."
Bailey says it is not by chance that some of the best endurance performers in the world are born and bred at high altitudes, and therefore adapted to a low-oxygen environment. For the rest of us, who can't select our past, our environment or our parents, bringing the mountain to the athlete is the solution.
Next month, athletes from more than 200 nations will compete, inspired by the Olympic motto "Citius, Altius, Fortius" - "Faster, Higher, Stronger". It's the perfect stage for world record attempts, with steady improvements made over the years in how fast Olympians run, how high they jump and how far they throw objects. But is there a limit to human performance?
The battle between scientific prediction and athletic performance has a long and embarrassing history. Less than 50 years ago, scientists were confident that a 100m sprint in less than 10 seconds would be physically impossible. They predicted that the forces generated would simply tear the body apart. Yet the Jamaican athlete Usain Bolt has run it in 9.58 seconds. A marathon run in less than 2 hours and 15 minutes was considered equally impossible, but not for Kenya's Patrick Makau, who recently set a world record of 2:03:38.
Bailey's research turns conventional wisdom on its head. It has not been an easy journey for Helen Jenkins. Her husband, too, has faced adversity. At the 2004 Athens Olympics, Marc Jenkins was forced to carry his bike for 2km after a competitor collided with him, damaging his wheel. He crossed the finish line in last place, but his heroic efforts embodied the Olympic spirit and won him instant fame. The next year, he battled life- threatening deep vein thrombosis and a pulmonary embolism. But like his wife, he has returned to full health.
Both feel that training in a low-oxygen environment has contributed to this positive outcome. From her first session gasping for air while merely sitting in the chamber at 12 per cent oxygen (equivalent to 4,500m of altitude, but without any acclimatisation), Helen's body and brain slowly became used to the low-oxygen environment. As a result, her performance has improved.
"Squeezing an extra 1 per cent out of Helen will represent the difference between an athlete finishing on the podium or just being another forgotten race statistic," Marc says. "It's all about mind over matter."
For Olympic resources on every subject, check out the new TES Resources London 2012 collections.
Key stage 1: Brain training
Get pupils exercising their little grey cells as well as their muscles with tintin_magley's brain gym starters.
Key stage 2: Olympic insides
Give your science lessons a sporty theme with philsha's Olympic investigations.
Key stage 3: Respire
Help pupils to understand the respiration system with a detailed scheme of work from raj.nandhra.
Key stage 4: Aerobic v anaerobic
How does oxygen affect athletes' performance? Find out with funforester's presentation.
Key stage 5: Altitude exercise
Delve deeper into the world of neurobics with an extensive scheme of work from icefarris.
Find all links and resources at www.tes.co.ukresources040.