Are Running Prosthetics Unfair? The Science of Oscar Pistorius and Blake Leeper's Legs | Corporis

in February of 2020 an international athletics committee decided that Blake Leeper a 30 year old Olympic hopeful wouldn't be allowed to compete in the 2020 Summer Games they decided his prosthetic running legs or blades gave him an advantage over his able-bodied competition a similar case was made back in 2007 against South African Oscar Pistorius which was strengthened by a study from German researchers they claimed that his prosthetics conserved a disproportionate amount of elastic energy and gave him an advantage pistorius's legal team found that the study was poorly designed and and follow-up research done at Rice University a separate research team found that while his running mechanics were different they were negligible compared to metabolic factors like cardiovascular fitness especially for a longer race like the 400 meter that he competed in and that leaper competes in today Pistorius was allowed to compete and became the first athlete with amputations to qualify for the Olympics but new science and new rules have come out since then so what does the new science say and do these prosthetics kiev runners and advantage [Music] this whole controversy is only possible because of very recent technology like thinking about the big picture we just got to the point where individuals with leg amputations can exercise let alone compete with Olympic athletes with the traumatic injuries of World War 1 and to the need for prosthetic limbs skyrocketed young veterans returning from war requested better engineering for this piece of technology they live with for the rest of their lives these were young people who wanted to stay active so engineers had to come up with a design that let the user do more than just sit and stand and one of their initial challenges was to come up with different exercise prosthetics that can be used at different levels of amputation the shorter that residual limb is the harder it is to walk the same goes for more aggressive exercise someone with a single trans tibial or below the knee amputation can still jog with a prosthetic but someone with two above the knee amputations might be limited to arm exercise and for a long time folks with amputations using their normal walking prosthetics for more intense exercise that's one reason why a new running specific prosthetic introduced in the 80s was such a big deal from an engineering perspective optimizing one joint for one activity in this case running is much easier than imitating multiple joints for a multi-purpose prosthetic this J shaped foot was built out of a stiff carbon fiber meant to imitate the strength and springiness of the biological calf muscle plus a loose prosthetic is a waste of energy so the flex foot had a deep form-fitting socket to minimize energy loss a few years later the icelandic company asher got rid of the heel increased the stiffness and tweaked some materials and came out with the flex sprint a design that would stay pretty consistent up to modern day as more athletes adopted the new prosthetics the finish times between able-bodied runners and runners with amputations got closer and closer especially for longer distance races Usain Bolt's best 100-meter dash time is 9.5 8 seconds while the fastest Paralympic athlete Alan Olivera ran it in 10.5 seven seconds about ten percent slower that gap closes a little bit at distance though the able-bodied record for the 400 meter is forty three point zero three seconds while the fastest runner with amputations ran it in forty five point three nine seconds a much smaller relative gap than the hundred that athlete was Oscar Pistorius which is where the controversy begins Pistorius started competing with able-bodied athletes and placing well it wasn't winning but he was placing well and in 2007 the International Association of Athletics Federation or IAAF changed a rule that said any tool that you springs to give the athlete an unfair advantage wouldn't be allowed in competition but what's an unfair advantage depends who you ask by this point in history we did have some research that showed that runners with prosthetics ran differently than able-bodied runners so a group of German researchers hooked Pistorius to a bunch of sensors use some high-speed cameras and analyzed his form see when a biological foot touches down the ankle has to slow you down as the body lands then muscles have to contract again as the person takes an step some of the energy can be stored and released in the springy muscles but according to this study the prosthetic ankle stored in released energy much more efficiently than muscles good that study determined that the prosthetic saved energy which saved the athlete's body energy which gave him an advantage but the German research group never actually measured any metabolic factors only kinetic ones if the prosthetics did let his body save energy we should see that reflected in his heart rate and his vo2 or his oxygen consumption so researchers at Rice University did a follow-up study focused on metabolic factors and on every test from vo2 max to running economy he performed similar to able-bodied runners yes his prosthetics gave him different mechanics but it didn't give him the physiological edge that the Germans predicted that study overruled the IAAF decision and allowed Pistorius to run in future events now this is only the start of the story why because that stimulated a huge wave of research in that area a study from Georgia Tech in 2009 tested running economy and a few other measures of aerobic fitness on able-bodied runners and single limb amputees with a normal walking prosthetic and those same amputees with running prosthetics in a surprise to nobody the amputees measured better in every metric when they ran in the blades that study confirmed the earlier findings that below the knee amputees could achieve similar levels of aerobic fitness compared to their able-bodied competition so future research went deeper into the mechanics questions in particular the three determinants of top speed step frequency which is how fast you can move your legs contact length which is the distance that your body moves while your foot is on the ground and average mass specific force how forcefully you push off the ground with each step improve any of those and you should be able to run faster those earlier studies show that Pistorius did have a higher step frequency his prosthetic legs were lighter than biological legs which let him move them extra fast with extra time between steps he should be able to generate more force but again nobody had studied that with science yet in 2010 researchers studied the forces generated by single leg amputees affected leg and compared it to their non affected leg the affected side generated 9% less force than the intact limb and to the research team that made a lot of sense the affected side didn't have a calf muscle to generate new force so to more accurately compare a biological leg to a prosthetic leg in a 2012 experiment they had to imagine the leg as a spring the body center of gravity is represented as this circle and the leg as a massless spring attached to a contact point on the ground when you take a step and land on your foot the weight of the body compresses the spring giving us a change in height of the circle or body when the body is moving horizontally like during running the spring looks like this the center of mass starts here and the spring is uncompressed as you transfer your weight onto your foot the spring compresses then your body moves forward and the spring recoils if we divide the peak vertical forces over this vertical motion we can calculate the stiffness of that athletes leg while it might not make sense to compare raw force generation the researchers knew that increased leg stiffness generally meant higher top speeds so at least they had some metric that they could kind of compare apples to apples with they recruited single and double leg amputees as well as able-bodied runners as controls and used a special force sensing treadmill to measure the force exerted by each footstep as the participants went through different speeds as speed increased the biological leg stiffness stayed constant or even increased but in both the single and the double leg amputees stiffness decreased in the prosthetic leg because the change in vertical motion got bigger at higher speeds while the ground forces stayed the same you can see this vertical motion firsthand too if you just go outside joggers tend to bob up and down while they run while a sprinter will be relatively level as they go through their sprints follow-up research in 2013 try to confirm where the vertical motion came from and it turned out to be the amputees hips they found that able-bodied runners landed with higher force throughout their hip while amputees landed more softly with their hips the researchers described this as more of a shock absorber than a spring by this point in history Oscar Pistorius had already run in the 2012 Olympics and would stay mostly out of the news now different versions of running prosthetics were still being developed while all of this was happening some had different heights and different stiffnesses so scientists focus their research on the differences in the prosthetics themselves research published in 2016 played around with different settings and saw if combinations of model and blade shape and height and blade stiffness could influence overall stiffness one of the big takeaways was that as the angle of impact increased like a leg would experience at faster speeds stiffness decreased they tested that with treadmill running and with machinery that compressed the prosthetic while on an incline starting in 2018 leaper got in the spotlight and that's when the controversy started all over again he ended up setting a 400 meter world record for bilateral amputees which was also the tenth fastest in the entire world or at least it would have been at the IAAF counted it's the ruling in place by the IAAF said rule 144 a mechanical aid is not allowed unless the athlete can establish on the balance of probabilities that the use of an aid would not provide him with an overall competitive advantage so now the burden of proof is on the athlete and proving a negative is nearly impossible to do the years of previous research hadn't pointed to an obvious advantage from the prosthetics but people still wondered if different prosthetics were maybe more of an advantage than others similar to that 2016 paper research published in PLoS ONE and 20/20 compared multiple combinations of prosthetics on runners with bilateral trans tibial amputee shion's runners exactly like leaper and saw whether any influenced top speed the only thing that improved speed was the shape of the blade J shaped blades resulted in 8% faster speeds than C shaped blades due to the crater elastic energy returns neither stiffness nor longer blade had any kind of benefit their final line in the paper is even more clear based on our findings we encourage the governing bodies of athletics to adopt regulations based on scientific evidence to the author's prosthetics weren't advantages as of February of 2020 World Athletics who used to be IAF still banned leaper from competition with able-bodied competitors based on that unfair advantage arguments and that's where we're at right now so to recap this whole thing we know that able-bodied runners and runners with amputations have different biomechanics they do run differently but they have comparable physiology something else to keep in mind is that these experiments all had really small sample sizes which makes sense it's really hard to get a large number of athletes with this specific type of amputation that run at the elite level so this story doesn't have a clear conclusion the rules are kind of ambiguous and the science is complex that's where at if you want another running 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Channel: Corporis

Views: 8,544

Rating: 4.9509201 out of 5

Keywords: patrick kelly, patrick kelly science, anatomy, physiology, kinesiology, oscar pistorius, prosthetic leg, anatomy and physiology

Id: CNhn711-rLM

Length: 12min 8sec (728 seconds)

Published: Wed Apr 01 2020