Britain's Paralympic swimmers are the heroes of this winter's sporting calendar. Gareth Chadwick finds out how they applied science to training

While England's cricket team was receiving its worst Ashes drubbing for 85 years in the Australian sunshine earlier this winter, halfway around the world a team of remarkable British athletes was scoring a spectacular success.

At the International Paralympic Committee's (IPC) Swimming World Championships in South Africa in December, four gold medals on the final night saw Britain topping the medals table for the first time in its history.

The 33-strong team's record haul of 24 gold, 14 silver and 14 bronze medals left them one gold clear of their second-place rivals, the US. The IPC Swimming World Championships are a huge event on the disabled swimming calendar, second only to the Paralympics in terms of size and prestige.

For the team's official biomechanist Dr Carl Payton, contributing to such success on a major international sporting stage is one of the highlights of his career.

Biomechanics is the scientific study of forces and the effects of those forces on and within the human body. In sport, it's about making technique as good as possible and avoiding injury.

It has its roots in physics and mechanics and then applies elements of those sciences to the human biological system. The aim is to gain a greater understanding through measurement and analysis of the physical and mechanical forces that contribute to a particular movement, and to use that understanding to improve performance and technique.

"Biomechanics has a key role to play in an sport that is technique-based," says Payton. "There are two main objectives, either to improve performance or to make adjustments to technique in order to reduce the risk of injury."

Perhaps one of the best known examples of biomechanics in action is the British world record triple jumper Jonathan Edwards. Edwards refined his technique by using biomechanical analysis during a spell at Florida State University in the United States.

His coach used biomechanics to calculate that a longer take-off, coupled with raising the torso, holding the hop and step phases and controlling the pumping of the arms, would produce a longer jump.

The following year, Edwards improved his own personal best by half a metre and smashed the world record at the World Championships in Gothenburg in 1995, in the process setting a record that still stands.

Payton, a former competitive swimmer, is a senior lecturer in the exercise and sport science department at Manchester Metropolitan University, one of only five five-star rated sports science departments in the country. He is also a BASES high performance sport accredited biomechanist. He discovered biomechanics when his own swimming coach gave him a book to read in order to try and improve his performance.

"Rather than saying this is what you need to do to swim better, the book broke it down in to specific movements, explaining why each was important and precisely how they affected your swimming. That mix of mechanics, physics and biology fascinated me," he says.

He did a degree in human movement studies in the mid-1980s ("there weren't a lot of dedicated sports science degrees around then," he says), before specialising in biomechanics and physiology for a Masters degree at Loughborough University.

He says that working with the British swimmers fulfils not only his personal love of swimming, but also the professional motivation of applying biomechanics to a particularly challenging sport.

"Swimming is a dual medium sport. It is in the water, but it is also in the air, which makes it a particularly challenging yet rewarding sport to study. On the one hand, it is a harsh environment in which to collect your data and do your analysis, but at the same time it really lends itself to biomechanics because the techniques involved are so complex," he says.

Biomechanists do not work alone. They are part of a team that includes sports psychologists, nutritionists, physiotherapists and medical support, all working closely with the coaches to fine-tune the athletes' performances.

Payton has been working with the disabled swimming team since 2000. He visits each of the three high-performance swimming centres in the UK (Stirling, Swansea and Manchester) at least three times per year, analysing the swimmers' techniques and performance. He also attends a lot of competitions, both in the UK and abroad, producing race and competition analyses. It is an intense schedule. As soon as one competition is over, the focus is straight on to the next. Just weeks after the success in South Africa, the attention now is on the 2008 Olympics in Beijing.

Some of the biomechanical support he provides is immediate, based on video analysis and watching from the poolside. But there is a vast range of specific techniques and processes to draw on. Kinematic analysis, for example, uses high speed cameras and three-dimensional images to study a particular movement, producing a very detailed picture of what the athlete is doing, such as the range of motion, rate of movement, or rate of acceleration, both in and out of the water.

Kinematic analysis doesn't reveal anything about the forces involved in that movement, however. So a second technique is to measure the forces that are acting on and within the athlete's body, such as tethered force analysis, where the swimmer is tethered to a force transducer which measures the forces the swimmer produces, the stress levels they produce and how well they are sustained over a period of time.

"It enables you to understand why certain injuries occur. Once you have that, you can start to modify the technique to reduce the risk of those injuries," says Payton.

Another innovation is the velocity metre, which measures the instantaneous speed of the swimmer. So rather than measuring their speed over one length or 10 metres, it takes 100 speed measurements per second, revealing how their speed fluctuates within a single stroke. Such detailed information enables the biomechanist to identify the areas where propulsion is less effective and what specific aspects of the stroke could be changed to improve their overall speed.

It is all highly technical and evidence-based. There is no room for assumptions or guesswork. Every suggestion that the biomechanist makes about tweaking a movement or changing part of the technique is based on hard factual evidence gleaned from in-depth scientific research.

Payton says: "Some of the changes you suggest may take a day or a week to implement, but if you are suggesting they change something like their timing, which could easily take six months, you have to be very confident that it is actually going to make them swim faster at the end of it."

The fact that the swimmers are disabled, says Payton, makes it even more challenging - not to mention rewarding when the team is successful, as in South Africa.

"There are biomechanics text books for able-bodied swimmers, but they are no use whatsoever when working with a swimmer who can't use her legs, or is affected down one side because he is hemiplegics. What is the best way for those swimmers to swim? That's a challenge that only sports biomechanics can answer. That's what keeps me motivated."