Do Blade Prostheses Give Amputee Runners an Advantage?

Underneath the resilience and perseverance shown by world-class adaptive athletes is an ongoing debate about their “unfair advantage,” which has prevented some athletes from competing. Do carbon-fiber prostheses give adaptive athletes an advantage over their non-amputee competitors? Are they capable of running faster and performing better because of their prostheses?

The debate began in 2008 when Oscar Pistorius, a double-amputee sprinter, was banned by the International Association of Athletics Federations (IAAF) from competing against non-amputee athletes. Pistorius eventually prevailed. Fuel was added to the debate in 2014 when Markus Rehm, a German national long jump champion, was barred from competing in the European Championships in Zurich. Unlike Pistorius, Rehm was prevented from competing. So, what was the difference between these two cases? 

The similarities and differences of blades and biological legs  

Because of these two high-profile athletes, an investigation was launched into the nature of running blades and whether they give adaptive athletes an unfair advantage over their competition or not. Both athletes turned to the scientific community to help them build their case, proving that the running blades don’t give them an unfair advantage. 

The series of tests found that blade prostheses share some similarities with biological legs. The running blades store energy as it bears the user’s weight. The energy is then released as the runner pushes off the ground. This process mimics the way Achilles’ tendons and calf muscles spring and recoil.

The difference lies in the foot. A biological foot consists of muscle cells that create metabolic efficiency when the athlete pushes off the ground. This gives the muscles some leeway, so it doesn’t have to work hard to sustain every step while running. 

In contrast, blade prostheses do not pivot nor generate energy. This means that amputee runners need to exert more effort while running. As running with a prosthesis places more stress on the body, adaptive athletes need to work hard to strengthen their body and offset the “prosthetic factor.” 

Another difference is its adaptability. A non-amputee runner can easily adjust the hardness of his or her leg muscles as well as the angle of the foot to adapt to changes in the terrain.

Meanwhile, an amputee runner cannot adjust the hardness or angle of his or her blade on the fly. Once the prosthesis has been fitted to the runner, it is also custom-optimized to run under specific conditions. The passive nature of prosthetic limbs is the reason a sprinter needs to use a different prosthesis than that of a marathon runner.

However, it’s not all bad news. Using running legs has its competitive benefits. Once an amputee runner reaches top speed, the blade prostheses allow him or her to move faster and with less effort. This is because the running blades typically weigh less than biological legs.

Pistorius’ case  

Researchers who worked on Pistorius’ case concluded that he used 17% less energy than that of non-amputee elite sprinters. They also found that it took him 21% less time to swing his legs between strides. According to Peter Weyand from the Southern Methodist University and Matt Bundle of the University of Montana, the findings present a clear advantage for Pistorius. A faster leg swing and an energy-efficient stride can create up to a seven-second lead.

In contrast, other researchers thought that there was insufficient evidence to Pistorius’ advantage. In a paper published in the Journal of Applied Physiology in April 2010, Rodger Kram, Alena Grabowski, Craig McGowan, Mary Beth Brown, and Hugh Herr provided convincing counter-arguments that the IAAF ban was overturned. Pistorius went on to become the first amputee to compete in the Olympics at the 2012 Olympics in London.

Rehm’s case  

To get the IAAF to overturn their decision in time for the 2015 Rio de Janeiro Olympics, Rehm approached Grabowski to help him prove that his blade did not give him an unfair advantage. However, unlike Pistorius, the findings were inconclusive.

Unlike sprinters, long jumpers require both a vertical and horizontal propulsion. The goal is to get as high in the air as possible without losing forward velocity.

Grabowski and her colleagues found that long jumpers with a below-the-knee amputation use a different technique than athletes who do not need a prosthesis. Although the blade, like the one Pistorius used, had a passive nature, which limits a jumper’s top sprinting speed, the tests found that it offers a significant advantage: enabling better takeoff.

More findings  

As prosthetic technology continues to improve, researchers are continually trying to find answers to whether prostheses provide adaptive athletes unfair advantage over competitors with biological limbs or not.

Following the series of tests for Rehm, Grabowski, Kram, and Paolo Taboga found that the side of the body where the prosthesis is attached affects speed, especially when the athlete runs on a counter-clockwise curved track. An adaptive athlete who wears a left leg prosthesis is generally 4% slower than those wearing a prosthesis on the right leg in track events of 200 meters or more.

The researchers looked into the effect of prosthesis height after Pistorius complained that Brazilian sprinter Alan Oliveira was faster because his blades were longer. Oliveira beat Pistorius in the 200-meter race in the 2012 Paralympic Games. But according to Toboga, although longer legs can mean taking longer steps, it can also take a bit longer to swing the leg, resulting in fewer steps. This means that the length of the leg does not have any significant effect on speed.

According to Grabowski, figuring out the ideal length is difficult because many amputations are the result of congenital conditions. This means some individuals may have different arm or femur lengths compared to an average non-amputee.

A long journey  

Research findings into the performance of different types of athletic prostheses are used to inform decisions in the sporting world. These findings are also being used to improve the process of matching prostheses based on the adaptive athletes’ abilities and choice of sport.

However, Grabowski said that the debate about performance wouldn’t go away any time soon. There are many disadvantages to consider on the part of the adaptive athlete such as energy loss, limitations in ankle push-off during acceleration, and energy loss, among others.

Perhaps the only way to stop the debate is to create a prosthesis that’s as good as a biological limb. Until that day comes, the scientific community will be working to create an even playing field for non-amputee athletes and adaptive athletes alike.