At this year’s World Para Athletics European Championships, Markus Rehm, a German athlete whose right leg has a below-the-knee amputation, notched 8.48 meters in the men’s long jump. With that performance, the 30-year-old athlete improved upon his previous Para Athletics record by a centimeter while also besting the gold-winning long jump at the 2016 Rio Olympics by ten centimeters.
Even before this career highlight, Rehm indicated in 2017 that he wanted to expand his competitive field and go head-to-head against nonadaptive athletes. But so far, that’s a goal he’s been unable to accomplish, because the International Association of Athletics Federation considers Rehm’s prosthetic blade a “technical aid” that might grant him an edge in competition. And per IAAF rules, it’s the athlete’s job to prove that their prosthetics won’t confer an advantage. This is a task few have taken on.
Rehm’s case inspired Alena Grabowski, a physiologist at the University of Colorado Boulder, to take a closer look at how prosthetics affect long-jump performance. In 2008, Grabowski’s research was instrumental in the case to allow Oscar Pistorius, the first double-amputee runner to compete in the Olympics, to participate in the 2012 London Games. This was after an IAAF-commissioned study found that his prosthesis could give him an advantage, research that Grabowski says she had “major issues” with its methods. More generally, the IAAF’s decision to put the burden of proof on the athlete in such cases, she says, isn’t based on any science she knows of.
In August, Grabowski worked with Blake Leeper, a sprinter with two below-the-knee amputations whose times are even faster than those of Pistorius. For Leeper, Grabowski looked at how his prostheses affected his top speed, acceleration out of the starting blocks, and navigation around curves. She plans to compare these observations with data from both adaptive and nonadaptive athletes.
Now Grabowski is working with long jumpers to see if there’s evidence that prosthetics might provide an extra boost in that sport. Her previous research on the topic suggests that while the blade might slow the approach to the long-jump pit, its spring might give a boost on the takeoff. But the science is still unclear. “It’s very tricky to have compelling evidence to say that you don’t have an advantage,” says Grabowski, who is an avid trail runner herself.
Her current test includes 20 competitive long jumpers, ten of whom have an amputation. (At the time Outside spoke to Grabowski, she said Rehm had shown interest in joining the research project but had not yet confirmed if he would.) The team at CU Boulder is using a tool in jump-off platforms called a force plate; it measures the athletes’ acceleration and works like a bathroom scale dial, moving as they jump up and down. The athletes also wear reflective dots so the scientists can track their motion. First, Grabowski and her team will assess what a typical competitive jump looks like for all the athletes in terms of run-up speed, takeoff velocity, and jump distance. Then she will manipulate the athletes’ performance to reveal the different physics of running and jumping with prostheses and without.
Of course, it’s impossible to have a side-by-side comparison of what it’s like for the same person to run and jump with and without an amputation. But Grabowski has a plan to get around this. The ten nonamputees will jump off multiple springy platforms that simulate how a prosthetic limb compresses. Each platform will be a different stiffness, which will help researchers observe how the amount of spring influences forward movement and whether the springs increase or decrease the length of the jump. “Can you jump farther in the horizontal direction if you have a spring underneath you?” Grabowski asks. “In the vertical direction, you could probably argue that you could jump up higher, but horizontally, it’s a little bit trickier to find that out.” For the amputee trials, the athletes will test different prosthetics that vary in stiffness. There’s an ideal medium between a blade that easily bends and one that doesn’t compress—if the device gives too easily under pressure, it saps the force needed to spring forward. But a too-stiff prosthetic doesn’t provide much boost in the leap.
Grabowski’s work might not only inform decisions around competing with prostheses; it may also help advance the devices themselves. “The bigger picture is to try to improve upon the design and try to make something that’s even better than what we have right now,” she says.
Grabowski plans to have results from the trials in fall 2019. And while she says IAAF standards are unclear when it comes to evidence for proving that prosthetics don’t provide a competitive advantage, she still anticipates her research will be useful for future decisions. “I’m hoping that we can at least start to inform [the IAAF] about what prostheses can and cannot do,” Grabowski says.