Paralympic athlete

Paralympic technology

Paralympians have been grabbing the headlines, as has the technology competitors use. Is the Paralympics a richer ground for innovation than the Olympics?

An issue of fairness has long been a red flag to research teams aligned with privileged first-world Paralympics teams such as Great Britain, Australia and Japan. Initially introduced in 1948 as an initiative to get wounded war veterans back into sport, many argue that the modern-day use of advanced technology in the Paralympics puts teams without multi-million pound commercial partnerships at a disadvantage. At Beijing's 2008 Paralympics, for example, a South African runner ran with his right leg on a prosthetic leg meant for the left side, while Australian Kelly Cartwright ran on a bespoke carbon fibre blade costing somewhere in the region of $1,500.

While the privileged few, such as those from Team GB, acknowledge that the playing field is not necessarily level, they argue that the competition has moved on from its early ambitions. Vicky Tolfrey, reader in applied disability sport at Loughborough University Sports Technology Institute and an expert in wheelchair sports, says the Paralympics has become just as much about pushing boundaries and breaking records as its Olympic counterpart.

"I work with sportsmen and women who engage in wheelchair sports," she says. "I'appreciate that there are some countries that just can't afford a titanium wheelchair, but I suppose I take perhaps a rather selfish approach in terms of prioritising high performance. In the UK we have got the funds and the resources, so let's use them."

Blade runner

Once a revolutionary piece of kit, the running blade made famous by South African runner Oscar Pistorius has now become the norm on the Paralympic running circuit. Contrary to some schools of thought, a sports running blade cannot equip the user with a more superior running function than an able-bodied athlete, as it does not include a motor or external power source like some non-sporting prosthetics on the market. Running blades are the only way to replicate the leg's natural ability to efficiently create and apply the power and movement needed to run.

Two types of running prosthesis exist: above and below the knee. Both of these consist of a carbon fibre blade interfacing directly with the athlete's existing limb. "Below the knee is very similar to Oscar Pistorius's running blades, which is a blade attached to a socket which simply attaches to the leg below the knee, whereas an above-the-knee blade will also feature a mechanical knee joint," says Anna Parisi, manager of partnerships and PR at prosthesis manufacturer Ottobock, who will be providing the 4,200 athletes competing at the Games with repairs for orthoses, prosthetics and wheelchairs.

Hydraulic cylinders in the knee joint in an above-the-knee blade are controlled directly by the athlete and allow the knee to straighten and bend, meaning less energy is lost when the athlete propels him or herself forward. The blade, or foot, is manufactured from over 80 layers of carbon fibre, with the ratio of layers depending on the physical impairment of each athlete. As only the forefront of the foot is used for running, the blade does not feature a conventional heel.

As in many other sports, carbon fibre is the material of choice due to its dampening properties, meaning minimal energy is lost during running; it also protects athletes' joints from repetitive impact. During running the carbon fibre compresses, propelling the athlete forward by transferring energy from athlete to the blade, and as the pressure is released the running blade returns to its original shape, channeling the stored energy to the athlete.

The shape of the running blade is adapted for each sport; for example, a marathon runner will use a blade that prioritises comfort over long distances, whereas a sprinter will favour a blade designed for speed and higher levels of propulsion. Silicone liners in the socket prevent blistering and discomfort. Suction valves can also be used to provide a seamless connection between the skin and the prosthetic, further reducing energy loss.

Wheels of speed

Envy is a universal driver across the sporting disciplines. Just as Wayne Rooney's new football boots become a coveted item the moment he showcases them on the pitch, if the highly successful Canadian Paralympic rugby players are seen reducing the calibre of their wheelchairs, reductions are likely to be seen on Team GB's equipment soon after. All wheelchairs must be priced at a rate that they can be made commercially available, something that Team Japan has come up against when designing its high-tech chair with partner Honda.

"Paralympic athletes often know better than their trainers what they will perform best in, and as a result our research has become much more evidence-based." says Tolfrey. "We listen to the perceptions of individual athletes. For example, they tell us they would like their wheel-sizes increased or decreased because they think it will improve their mobility around the court, or their straight-line sprint performance. We characterise aspects of wheelchair sport that are important to performance, such as pushing or pulling the chair backwards to get out of the defensive position, then seek innovative ways to measure these characteristics."

Tolfrey uses a gyroscope fixed to the wheels of a wheelchair called a velocometer to look at the inter-push profile of an athlete, examining acceleration and deceleration of the chair. Unlike regular cycling, where an athlete's foot has constant contact with the pedal, wheelchair propulsion is what's known as a discontinuous activity, so to increase the speed of acceleration the movement of each athlete must be broken down push by push, scientifically examining cause and effect of the force of exertion behind each arm movement.

Key areas that Tolfrey prioritises are rolling resistance and the mechanical efficiency of the wheelchair. This is not dissimilar to studying the physiological and biomechanical efficiency of an able-bodied athlete, except in Paralympic research the main focus is how the chair is propelled forwards and backwards more efficiently.

"What excites me about working with the Paralympic athletes is that you also have the physical impairment that you must consider, and this impairment is the function point of the athlete. As each athlete has different physical function, the knowledge is not as transferable between players and you have to take a very individual approach."

Racing ahead

Wheelchair racing began with a human factors requirement captured by BAE Systems in 2009, with the aim to look directly at the performance of each component of the wheelchair and its direct effect on performance.

Alison McPherson is research and innovation coordinator at UK Sport, which partnered with BAE Systems to carry out research based on aerodynamic engineering of the chairs in relation to the drag of differing body positions. Computational fluid dynamics (CFD) modelling was done on varying degrees of athlete body position in a wheelchair, before a rotating chair was placed and monitored in a BAE Systems wind tunnel.

It was apparent from testing that as well as wheel size, the interface between a Paralympian and a chair was of paramount performance. "We found that even if a position was the most aerodynamic from wind tunnel testing, if it was uncomfortable to hold it was an insignificant result," says McPherson.

While many chairs are made from titanium or aluminium for lightness, there is research being conducted to make the chairs even lighter by addressing each component individually and looking at new composites. As with running blades, carbon fibre has become the material of choice for sport wheelchair manufacturers. The challenge for designers and manufacturers is that sporting wheelchairs are exposed to short bursts of extremely high-impact activity, and as a result components susceptible to weakening must be made out of heavier, more hard-wearing materials.

When designing their carbon fibre frame, UK Sport conducted manipulations of models with BAE Systems, using CAD to determine stress points in the chair and improve the stiffness. They found there was too much flex in the longitude north section at the front which meant the energy generated by an athlete to propel him or herself forward was lost in the frame. "The biggest challenge was interfacing a carbon fibre frame with an aluminium cage," says McPherson, "which we overcame by providing a flat plate on which the two could interface. The lightness of the frame has seen a marginal but relevant decrease of 100g, with a combined decrease of 240g in the wheels."

For the athletics arena, UK Sport redesigned the wheels of Team GB's racing wheelchairs as the only versions available were off-the-shelf bicycle wheels, which were not engineered for high impact on an outdoor track. The stiffness was increased by 3.2 in the development of the world-class wheels, which were constructed from carbon fibre, the first of their kind for wheelchair racing. Many chairs feature a steering mechanism called a compensator, which can be set to direct a chair around a bend once activated by an athlete.

UK Sport counts McLaren Applied Technologies and BMW among their commercial partners, a luxury many other Paralympic teams simply cannot afford. McLaren Applied Technologies supplied UK Sport with indoor player-tracking technology for wheelchair basketball and rugby. The software acts as an indoor GPS and exertion monitoring tool for each player, and is also used by Olympic athletes in training.

Slam dunk

When qualifying for the Paralympics, each wheelchair must go through a rigorous classification process including the measurement of bench-test function and wheel height. At the turn of the millennium, regulations were far more stringent; cushioning was removed and bent to determine its flexibility and wheel bases were painstakingly measured to monitor height. But today wheelchair restrictions are more fluid; basketball restrictions have evolved, embracing anti-tip measures in the form of an additional rear stabilising wheel to allow players greater range of movement when shooting and tackling.

RGB Wheelchairs provide the official chairs for wheelchair basketball and Tolfrey says designers and researchers take a similar approach to sporting restrictions as a high-end Formula One team. "We just go back to basics and say, 'what are the rules and regulations and how much can we push those?' and reverse-engineer from there. Technology is evolving and restrictions are adapting to accommodate this evolution, meaning games are faster and more skilful making the sport much more exciting to watch."

Classification for athletes is a complex scoring system that makes it fair to compete against other players of differing impairments. Each team has an allotted number of points (in wheelchair basketball's case 14) relating to the level of impairment and physical capacity of each player. Team GB amputee Terry Bywater would be considered a 4.5-point player as he still has trunk mobility and a good kinetic chain, affording him a larger shooting range. A one-point player, such as Abdi Jama, suffers from a complete spinal cord injury, meaning he cannot use his lower limbs as an anchor point and will require strapping for balance.

As wheelchair basketball is a dynamic sport, a player's core needs to have a certain degree of freedom, so Loughborough University pioneered the concept of a polypropylene moulded seat for lower point players. Ergonomically designed, high-back bucket seats are vital to performance as they provide stabilisation and prevent pressure sores. To provide the closest fit possible, the seats are manufactured using an initial process of plaster-of-paris moulding to ensure a tight fit, before vacuum-forming the polypropylene around the impression. The polypropylene is then fixed to an Evazote foam that can be cut to shape or moulded.

UK Sport used Olympic sponsor BMW's CAD facilities to model their new range of contour seating that might be featured in this years Paralympic Games. CAD designs by UK Sport were sent to BMW's rapid prototyping facility in Munich for laser centering, a technique used frequently in the automotive industry to calibrate components in BMW's cars. The seats are then manufactured in around 40 hours out of Duraform, a material with similar properties to polypropylene.

Both Loughborough University and UK Sport have much to be proud of in its technological contribution to both the Olympic and the Paralympic Games on its home turf this year. "It can be argued that sporting technology has advanced with three aims in mind," says David Howe, professor at Loughborough University. "To produce better performances, to increase the comfort for an individual, athlete or otherwise, and to enable an improvement in efficiency and movement. Technology is literally pushing the Paralympic movement." 

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