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GAINcast Episode 89: How Speed Happens (with Peter Weyand)

“People recognize the power of science, in terms of testing and numbers. But unless you’re involved in it it’s hard to appreciate the creativity that is also part of the process.” — Peter Weyand

The founder of modern sports performance training, Vern Gambetta, interviewed SMU locomotion researcher Peter Weyand about human speed and performance for his GAINcast show.

The GAINcast name is an acronym for the internationally recognized Gambetta’s self-made sports performance education, outreach and training efforts, Gambetta Athletic Improvement Network.

Gambetta’s 60-minute interview with Weyand posted Nov. 2, 2017, “Gaincast Episode 89: How Speed Happens (with Peter Weyand).”

In it, Weyand touches on the experiences early in his career as a high school and college athlete playing basketball and running track that sparked his pursuit of a research and academic career in sports science and human performance.

As a high school coach, Weyand’s early interest intensified, leading him to pursue advanced degrees and a scientific career exploring the mechanics of human locomotion and speed, including at the University of Georgia and then at Harvard’s Concord Field Station.

During that time, Weyand worked with early pioneers in the biomechanics and human performance field, including renowned researcher Dick Taylor. At the field station in particular, Weyand credits Taylor with mentoring young researchers in aggressively and fearlessly digging into basic science questions surrounding mammalian locomotion.

“It was wide open, anything goes. It wasn’t these reductionist questions …. It was anything under the sun you could cook up. And there was an insistence on good scientific questions, and a real integrative perspective on all of it. Those were my formative scientific experiences. People recognize the power of science, in terms of testing and numbers. But unless you’re involved in it it’s hard to appreciate the creativity that is also part of the process. There’s an art of doing science and Dick was a master of that. And everybody that came through that field station under his training, which is really a who’s who in our field in many respects, learned that art from him.”

Weyand is an expert on human locomotion and the mechanics of running. Research from his SMU Locomotor Performance Laboratory in SMU’s Annette Caldwell Simmons School of Education and Human Development has produced ground-breaking scientific findings about the science of human speed.

The lab focuses on the mechanical basis of human performance and includes physicist and engineer Laurence Ryan, an expert in force and motion analysis.

The Weyand lab’s most recent research found that the world’s fastest sprinter, Usain Bolt, has an asymmetrical running gait, contrary to the common notions about coaching and training for speed. Bolt’s asymmetry was discovered using the lab’s two-mass model tool, which the researchers have described in the Journal of Experimental Biology, “A general relationship links gait mechanics and running ground reaction forces.” The model can assess the crucial early portion of foot-ground contact — the impact-phase force and time relationships — from motion data only.

Weyand is Glenn Simmons Professor of Applied Physiology and professor of biomechanics in the Department of Applied Physiology & Wellness.

Listen to the podcast.

EXCERPT:

By Martin Bingisser
GAINcast

There are some basic questions out there that are difficult to answer, such as what limits human running speed. As technology advances, scientists can better study and start to answer this and other simple questions like what makes one athlete faster than another.

Dr. Peter Weyand has spent decades researching locomotion on both animals and humans. His work with elite sprinters has brought some interesting conclusions and is driving the field forward. On this episode of the GAINcast he joins us to discuss his research and its practical implications.

Listen to the podcast.

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Quartz: The science explaining how Usain Bolt became the fastest human in the world

The health and science reporter for Quartz magazine, Katherine Ellen Foley, covered the research of SMU biomechanics expert Peter Weyand and his colleagues Andrew Udofa and Laurence Ryan for a story about how world championship sprinter Usain Bolt runs so fast.

The article, “The science explaining how Usain Bolt became the fastest human in the world,” published Aug. 2, 2017.

The researchers in the SMU Locomotor Performance Laboratory reported in June that world champion sprinter Usain Bolt may have an asymmetrical running gait. While not noticeable to the naked eye, Bolt’s potential asymmetry emerged after the researchers dissected race video to assess his pattern of ground-force application — literally how hard and fast each foot hits the ground. To do so they measured the “impulse” for each foot.

Biomechanics researcher Udofa presented the findings at the 35th International Conference on Biomechanics in Sport in Cologne, Germany. His presentation, “Ground Reaction Forces During Competitive Track Events: A Motion Based Assessment Method,” was delivered June 18.

The analysis thus far suggests that Bolt’s mechanics may vary between his left leg to his right. The existence of an unexpected and potentially significant asymmetry in the fastest human runner ever would help scientists better understand the basis of maximal running speeds. Running experts generally assume asymmetry impairs performance and slows runners down.

Udofa has said the observations raise the immediate scientific question of whether a lack of symmetry represents a personal mechanical optimization that makes Bolt the fastest sprinter ever or exists for reasons yet to be identified.

Weyand, an expert on human locomotion and the mechanics of running, is Glenn Simmons Professor of Applied Physiology and professor of biomechanics in the Department of Applied Physiology & Wellness in SMU’s Annette Caldwell Simmons School of Education & Human Development, is director of the Locomotor Lab.

Read the full story.

EXCERPT:

By Katherine Ellen Foley
Quartz
Eight years ago, Usain Bolt made history in less than 10 seconds at the International Association of Athletics Federations World Championship in Berlin, Germany.

The Jamaican sprinter set the world record for the 100-meter dash, clocking in at 9.58 seconds. Since then, no one (not even Bolt himself) has been able to best that time. On Saturday, August 5, Bolt will once more run the 100-meter dash at the IAAF World Championship (assuming he makes it through the qualifying race on August 4). This will be his last race; Bolt is set to retire after this running season (there’s some speculation he may still race in the 2020 Olympics, although as of now Bolt has said he doesn’t want to).

There’s no such thing as a perfect human running machine. But Bolt comes close—thanks to a combination of having all the advantages of a natural-born sprinter and putting in the effort needed to minimize any of his disadvantages.

Broadly speaking, Bolt has the unique muscular build shared by most of the very best sprinters. All human muscles are made of a mix of slow- and fast-twitch fibers—as well as some that are undifferentiated, and will become slow- or fast-twitch depending on how we use them most often. Slow-twitch fibers are built for efficiency and use oxygen to generate energy from sugar. They’re most effective for activities sustained over a long period of time, like distance running. Fast-twitch muscle fibers are used to generate huge amounts of force, but they don’t use oxygen and as a result can’t carry us far. Training can help shape undifferentiated fibers into either slow- or fast-twitch, but for the most part the best runners were born with an imbalance of one or the other. Elite marathoners have way more slow-twitch fibers, and sprinters like Bolt have an abundance of fast-twitch ones.

The best sprinters also run with a different form than the rest of us. It’s not that they move their legs significantly faster; it’s that they hit the ground harder (paywall). Most of the force sprinters generate is directed straight into the ground for vertical movement; only about 5% is used to propel them forward, Peter Weyand, a physiologist studying human speed at Southern Methodist University in Texas, told Popular Science in 2013. The more force a sprinter can pack into the ground with a quick foot strike, the faster he or she goes.

In a 2010 study, Weyand’s lab conducted an experiment where subjects jogged, ran, and hopped on one foot on a treadmill. They found that the most force came from hopping, thanks to the leg’s longer airtime. The researchers then calculated that if a runner were to generate the maximum hopping force possible with each step, he or she’d be able to reach a speed of 19.3 meters per second (63.3 feet per second)—which would make for a 5.18 second 100-meter dash.

This is just a fun theoretical experiment; it’s impossible to actually sprint and jump straight up and down at the same time. But it appears Bolt generates a powerful punch to the track—maybe the most powerful ever.

Read the full story.

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How Stuff Works: Scientists Discover Something Mind-blowing About How Usain Bolt Runs

Journalist Patrick J. Kiger with the news site How Stuff Works covered the research of SMU biomechanics expert Peter Weyand and his colleagues Andrew Udofa and Laurence Ryan for a story about Usain Bolt’s asymmetrical running gait.

The article, “Scientists Discover Something Mind-blowing About How Usain Bolt Runs,” published Aug. 2, 2017.

The researchers in the SMU Locomotor Performance Laboratory reported in June that world champion sprinter Usain Bolt may have an asymmetrical running gait. While not noticeable to the naked eye, Bolt’s potential asymmetry emerged after the researchers dissected race video to assess his pattern of ground-force application — literally how hard and fast each foot hits the ground. To do so they measured the “impulse” for each foot.

Biomechanics researcher Udofa presented the findings at the 35th International Conference on Biomechanics in Sport in Cologne, Germany. His presentation, “Ground Reaction Forces During Competitive Track Events: A Motion Based Assessment Method,” was delivered June 18.

The analysis thus far suggests that Bolt’s mechanics may vary between his left leg to his right. The existence of an unexpected and potentially significant asymmetry in the fastest human runner ever would help scientists better understand the basis of maximal running speeds. Running experts generally assume asymmetry impairs performance and slows runners down.

Udofa has said the observations raise the immediate scientific question of whether a lack of symmetry represents a personal mechanical optimization that makes Bolt the fastest sprinter ever or exists for reasons yet to be identified.

Weyand, who leads the lab and its researchers, he is an expert on human locomotion and the mechanics of running. He is Glenn Simmons Professor of Applied Physiology and professor of biomechanics in the Department of Applied Physiology & Wellness in SMU’s Annette Caldwell Simmons School of Education & Human Development, is director of the Locomotor Lab.

Read the full story.

EXCERPT:

By Patrick J. Kiger
How Stuff Works
Jamaican sprinter Usain Bolt is the world record-holder in both the 100- and 200-meter, and winner of those events in the last three Summer Olympics. Bolt can hit a top speed of around 27 mph (43.5 kph), and has clearly established himself as the greatest sprinter of all time. But there’s something curious about his legs, and the way he uses them.

As the athlete prepares to run in his final world championship meet in London’s 2017 World Athletics Championships, taking place Aug. 4-13 and less than three weeks before Bolt’s 31st birthday, scientists are still trying to figure out just how the fastest human on the planet manages to achieve such incredible speed. Researchers at the Southern Methodist University (SMU) Locomotor Performance Laboratory don’t quite have the answer yet — but they’ve made a surprising discovery.

The researchers analyzed video footage of Bolt and other sprinters from the 2011 Diamond League race at the World Athletics Championships in Monaco. They also used a “two mass model” analysis tool they developed, which allows them to study the physical forces that a runner creates — without actually bringing Bolt into a lab and putting him on a treadmill. They found that Bolt had an uneven, assymetrical stride, which is something that scientists might have expected to slow him down.

When he runs, Bolt’s right leg strikes the ground with 13 percent more peak force than does his left leg, and with each stride, his left leg stays in contact with the track about 14 percent longer than the right. The researchers findings have been published in a new study in the Journal of Experimental Biology.

Bolt’s asymmetrical stride is probably due to his anatomy. As he recounted in his autobiography “The Fastest Man Alive: The True Story of Usain Bolt,” Bolt discovered as an adult that he has scoliosis, a condition in which his spine curves slightly to the left, which has forced his hips out of alignment so that his right leg is a half-inch (1.2 centimeters) shorter than the left. Bolt has written that he feels awkward standing still, and leans to the right because it feels uncomfortable to stand and place pressure on his left leg. Sitting in the same position for too long gives him backaches.

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Slate: Making the Perfect Sprinter More Perfect

How Usain Bolt could have run even faster.

Slate online magazine journalist Adam Willis covered the research of SMU biomechanics expert Peter Weyand and his colleagues Andrew Udofa and Laurence Ryan for a story about the world’s fastest sprinter, Usain Bolt, and whether he could possibly run even faster with different form.

The article, “Making the Perfect Sprinter More Perfect,” published Aug. 4, 2017.

Weyand, who leads the SMU Locomotor Performance Laboratory, is an expert on human locomotion and the mechanics of running. In his most recently published research, Weyand was part of a team that developed a concise approach to understanding the mechanics of human running. The research has immediate application for running performance, injury prevention, rehab and the individualized design of running shoes, orthotics and prostheses. Called the two-mass model, the work integrates classic physics and human anatomy to link the motion of individual runners to their patterns of force application on the ground — during jogging, sprinting and at all speeds in between.

His lab also reported in June that world champion sprinter Usain Bolt may have an asymmetrical running gait. While not noticeable to the naked eye, Bolt’s potential asymmetry emerged after the researchers dissected race video to assess his pattern of ground-force application — literally how hard and fast each foot hits the ground. To do so they measured the “impulse” for each foot.

Udofa presented the findings at the 35th International Conference on Biomechanics in Sport in Cologne, Germany. His presentation, “Ground Reaction Forces During Competitive Track Events: A Motion Based Assessment Method,” was delivered June 18.

The analysis thus far suggests that Bolt’s mechanics may vary between his left leg to his right. The existence of an unexpected and potentially significant asymmetry in the fastest human runner ever would help scientists better understand the basis of maximal running speeds. Running experts generally assume asymmetry impairs performance and slows runners down.

Udofa has said the observations raise the immediate scientific question of whether a lack of symmetry represents a personal mechanical optimization that makes Bolt the fastest sprinter ever or exists for reasons yet to be identified.

Weyand also has been widely interviewed in years past on the controversy surrounding double-amputee South African sprinter Oscar Pistorius. Weyand co-led a team of scientists who are experts in biomechanics and physiology in conducting experiments on Pistorius and the mechanics of his racing ability.

Weyand, who is Glenn Simmons Professor of Applied Physiology and professor of biomechanics in the Department of Applied Physiology & Wellness in SMU’s Annette Caldwell Simmons School of Education & Human Development, is director of the Locomotor Lab.

The researchers described the two-mass model earlier this year in the Journal of Experimental Biology in their article, “A general relationship links gait mechanics and running ground reaction forces.” It’s available at bitly, http://bit.ly/2jKUCSq.

Read the full story.

EXCERPT:

By Adam Willis
Slate
Usain Bolt is the only person to win both the 100 and 200 meters at three Olympic games. He is also the only person to do this at two Olympic games. Bolt has broken five individual outdoor track and field world records, three of them his own. He has run three of the five fastest 100-meter races and four of the six fastest 200-meter races in history. As Bolt gets set for the World Athletics Championships in London, the final meet of his beyond-illustrious career, we should be grateful for all the memorable moments the world’s fastest man has given us. We should also be ingrates and ask: Could he have run faster?

Bolt has an uncanny knack for making the incredibly difficult look easy—like Muhammad Ali coming off the ropes, like Westley fencing with his left hand, like James Joyce writing Ulysses from Paris. It’s only natural to wonder, then, if he could have done more. His midrace celebrations, his apparent aversion for practice and affinity for parties, his less than sensible diet—he reportedly ate 1,000 Chicken McNuggets in 10 days during the Beijing Olympics—all suggest history’s greatest sprinter might’ve had a little bit more in the tank.

After Bolt breezed to a 9.69 world record in the 100 meters at the 2008 Olympics, jogging and chest thumping across the finish line just days before his 22nd birthday, his coach Glen Mills made headlines with his claim that Bolt would have hit 9.52, at worst, if he had just run through the line. Scientists took on the task of projecting the time that might have been, with most concluding that 9.52 was, at best, a slight exaggeration. Bolt, though, made that claim look less sensational when he tore through his own world records at the world championships in Berlin a year later, posting 9.58 in the 100 and 19.19 in the 200. Still, Bolt would never reach the 9.52 that Mills estimated, nor, for that matter, the 9.4 that he himself predicted. He would never best those world records that he set in Berlin, when he was not yet 23 years old.

“We haven’t seen the 2009 Bolt since 2009,” says Peter Weyand, the director of the Locomotor Performance Laboratory at Southern Methodist University and a leading expert on the science of sprinting. When I asked Weyand about Bolt’s early peak, he told me that, although 22 or 23 is not an unusual age for a sprinter to top out, he would have predicted more after Bolt’s 2009 performances.

While recent research from Weyand’s lab concluded that Bolt’s stride is abnormally asymmetric, Weyand says it’s unlikely this asymmetry held Bolt back in any way. He does point, however, to several aspects of Bolt’s form that are considered unorthodox and potentially suboptimal.

Read the full story.

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The New York Times: Something Strange in Usain Bolt’s Stride

Bolt is the fastest sprinter ever in spite of — or because of? — an uneven stride that upends conventional wisdom.

The New York Times reporter Jeré Longman covered the research of SMU biomechanics expert Peter Weyand and his colleagues Andrew Udofa and Laurence Ryan for a story about Usain Bolt’s apparent asymmetrical running stride.

The article, “Something Strange in Usain Bolt’s Stride,” published July 20, 2017.

The researchers in the SMU Locomotor Performance Laboratory reported in June that world champion sprinter Usain Bolt may have an asymmetrical running gait. While not noticeable to the naked eye, Bolt’s potential asymmetry emerged after the researchers dissected race video to assess his pattern of ground-force application — literally how hard and fast each foot hits the ground. To do so they measured the “impulse” for each foot.

Biomechanics researcher Udofa presented the findings at the 35th International Conference on Biomechanics in Sport in Cologne, Germany. His presentation, “Ground Reaction Forces During Competitive Track Events: A Motion Based Assessment Method,” was delivered June 18.

The analysis thus far suggests that Bolt’s mechanics may vary between his left leg to his right. The existence of an unexpected and potentially significant asymmetry in the fastest human runner ever would help scientists better understand the basis of maximal running speeds. Running experts generally assume asymmetry impairs performance and slows runners down.

Udofa has said the observations raise the immediate scientific question of whether a lack of symmetry represents a personal mechanical optimization that makes Bolt the fastest sprinter ever or exists for reasons yet to be identified.

Weyand, who is Glenn Simmons Professor of Applied Physiology and professor of biomechanics in the Department of Applied Physiology & Wellness in SMU’s Annette Caldwell Simmons School of Education & Human Development, is director of the Locomotor Lab.

An expert on human locomotion and the mechanics of running, Weyand has been widely interviewed about the running controversy surrounding double-amputee South African sprinter Oscar Pistorius. Weyand co-led a team of scientists who are experts in biomechanics and physiology in conducting experiments on Pistorius and the mechanics of his racing ability.

For his most recently published research, Weyand was part of a team that developed a concise approach to understanding the mechanics of human running. The research has immediate application for running performance, injury prevention, rehab and the individualized design of running shoes, orthotics and prostheses. The work integrates classic physics and human anatomy to link the motion of individual runners to their patterns of force application on the ground — during jogging, sprinting and at all speeds in between.

They described the two-mass model earlier this year in the Journal of Experimental Biology in their article, “A general relationship links gait mechanics and running ground reaction forces.” It’s available at bitly, http://bit.ly/2jKUCSq.

The New York Times subscribers or readers with remaining limited free access can read the full story.

EXCERPT:

By Jeré Longman
The New York Times
DALLAS — Usain Bolt of Jamaica appeared on a video screen in a white singlet and black tights, sprinting in slow motion through the final half of a 100-meter race. Each stride covered nine feet, his upper body moving up and down almost imperceptibly, his feet striking the track and rising so rapidly that his heels did not touch the ground.

Bolt is the fastest sprinter in history, the world-record holder at 100 and 200 meters and the only person to win both events at three Olympics. Yet as he approaches his 31st birthday and retirement this summer, scientists are still trying to fully understand how Bolt achieved his unprecedented speed.

Last month, researchers here at Southern Methodist University, among the leading experts on the biomechanics of sprinting, said they found something unexpected during video examination of Bolt’s stride: His right leg appears to strike the track with about 13 percent more peak force than his left leg. And with each stride, his left leg remains on the ground about 14 percent longer than his right leg.

This runs counter to conventional wisdom, based on limited science, that an uneven stride tends to slow a runner down.

So the research team at S.M.U.’s Locomotor Performance Laboratory is considering a number of questions as Bolt prepares for what he said would be his final performances at a major international competition — the 100 meters and 4×100-meter relay next month at the world track and field championships in London.

Among those questions: Does evenness of stride matter for speed? Did Bolt optimize this irregularity to become the fastest human? Or, with a more balanced stride during his prime, could he have run even faster than 9.58 seconds at 100 meters and 19.19 seconds at 200 meters?

“That’s the million-dollar question,” said Peter Weyand, director of the S.M.U. lab.

The S.M.U. study of Bolt, led by Andrew Udofa, a doctoral researcher, is not yet complete. And the effect of asymmetrical strides on speed is still not well understood. But rather than being detrimental for Bolt, the consequences of an uneven stride may actually be beneficial, Weyand said.

It could be that Bolt has naturally settled into his stride to accommodate the effects of scoliosis. The condition curved his spine to the right and made his right leg half an inch shorter than his left, according to his autobiography.

Initial findings from the study were presented last month at an international conference on biomechanics in Cologne, Germany. Most elite sprinters have relatively even strides, but not all. The extent of Bolt’s variability appears to be unusual, Weyand said.

“Our working idea is that he’s probably optimized his speed, and that asymmetry reflects that,” Weyand said. “In other words, correcting his asymmetry would not speed him up and might even slow him down. If he were to run symmetrically, it could be an unnatural gait for him.”

Antti Mero, an exercise physiologist at the University of Jyvaskyla in Finland, who has researched Bolt’s fastest races, said he was intrigued by the S.M.U. findings.

The New York Times subscribers or readers with remaining limited free access can read the full story.

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Dallas Innovates: SMU Researchers: Usain Bolt’s Gait is Asymmetrical

The researchers assessed Bolt’s running using a new motion-based method to test how hard and fast each foot hits the ground.

Journalist Lance Murray with D Magazine’s Dallas Innovates covered the research of SMU biomechanics expert Peter Weyand and his colleagues Andrew Udofa and Laurence Ryan for a story about Usain Bolt’s asymmetrical running gait.

The article, “SMU Researchers: Usain Bolt’s Gait is Asymmetrical,” published July 5, 2017.

The researchers in the SMU Locomotor Performance Laboratory reported in June that world champion sprinter Usain Bolt may have an asymmetrical running gait. While not noticeable to the naked eye, Bolt’s potential asymmetry emerged after the researchers dissected race video to assess his pattern of ground-force application — literally how hard and fast each foot hits the ground. To do so they measured the “impulse” for each foot.

Biomechanics researcher Udofa presented the findings at the 35th International Conference on Biomechanics in Sport in Cologne, Germany. His presentation, “Ground Reaction Forces During Competitive Track Events: A Motion Based Assessment Method,” was delivered June 18.

The analysis thus far suggests that Bolt’s mechanics may vary between his left leg to his right. The existence of an unexpected and potentially significant asymmetry in the fastest human runner ever would help scientists better understand the basis of maximal running speeds. Running experts generally assume asymmetry impairs performance and slows runners down.

Udofa has said the observations raise the immediate scientific question of whether a lack of symmetry represents a personal mechanical optimization that makes Bolt the fastest sprinter ever or exists for reasons yet to be identified.

Weyand, who leads the lab and its researchers, he is an expert on human locomotion and the mechanics of running. He is Glenn Simmons Professor of Applied Physiology and professor of biomechanics in the Department of Applied Physiology & Wellness in SMU’s Annette Caldwell Simmons School of Education & Human Development, is director of the Locomotor Lab.

Read the full story.

EXCERPT:

By Lance Murray
Dallas Innovates
When it comes to running, nobody does it faster than Usain Bolt, the eight-time Olympic champion and triple world record holder.

The lanky Jamaican sprinter is known for his explosive acceleration down the track and the famous images of him looking back as he leaves his competitors in his wake.

You’d think Bolt’s powerful legs work as a symmetrical team propelling him at great speed toward the finish line, but according to researchers at Southern Methodist University, Bolt’s gait may, in fact, be asymmetrical.

SMU researchers examined the running mechanics of Bolt, who is considered the world’s fastest man.

The analysis, so far, suggests that his mechanics may vary from his right leg to his left, according to Andrew Udofa, a biometrics researcher in the SMU Locomotor Performance Laboratory.

According to a blog on SMU Research News, most running experts assume that asymmetry impairs performance and slows a runner down. This unexpected asymmetry in Bolt’s mechanics could help scientist better understand the basis of maximal running speeds, according to the university.

“Our observations raise the immediate scientific question of whether a lack of symmetry represents a personal mechanical optimization that makes Bolt the fastest sprinter ever or exists for reasons yet to be identified,” Udofa, a research team member, said in the blog.

Read the full story.

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Does symmetry matter for speed? Study finds Usain Bolt may have asymmetrical running gait

A new method for assessing patterns of ground-force application suggests the right and left legs of the world’s fastest man may perform differently, defying current scientific assumptions about running speed.

World champion sprinter Usain Bolt may have an asymmetrical running gait, according to data recently presented by researchers from Southern Methodist University, Dallas.

While not noticeable to the naked eye, Bolt’s potential asymmetry emerged after SMU researchers assessed the running mechanics of the world’s fastest man.

The analysis thus far suggests that Bolt’s mechanics may vary between his left leg and his right, said Andrew Udofa, a biomechanics researcher in the SMU Locomotor Performance Laboratory.

The existence of an unexpected and potentially significant asymmetry in the fastest human runner ever would help scientists better understand the basis of maximal running speeds. Running experts generally assume asymmetry impairs performance and slows runners down.

“Our observations raise the immediate scientific question of whether a lack of symmetry represents a personal mechanical optimization that makes Bolt the fastest sprinter ever or exists for reasons yet to be identified,” said Udofa, a member of the research team.

The SMU Locomotor Lab, led by Peter Weyand, focuses on the mechanical basis of human performance. The group includes physicist and engineer Laurence Ryan, an expert in force and motion analysis, and doctoral researcher Udofa.

The intriguing possibility of Bolt’s asymmetry emerged after the SMU researchers decided to assess his pattern of ground-force application — literally how hard and fast each foot hits the ground. To do so they measured the “impulse” for each foot.

Impulse is a combination of the amount of force applied to the ground multiplied by the time of foot-ground contact.

“The manner in which Bolt achieves his impulses seems to vary from leg to leg,” Udofa said. “Both the timing and magnitude of force application differed between legs in the steps we have analyzed so far.”

Impulse matters because that’s what determines a runner’s time in the air between steps.

“If a runner has a smaller impulse, they don’t get as much aerial time,” Weyand said. “Our previous published research has shown greater ground forces delivered in shorter periods of foot-ground contact are necessary to achieve faster speeds. This is true in part because aerial times do not differ between fast and slow runners at their top speeds. Consequently, the combination of greater ground forces and shorter contact times is characteristic of the world’s fastest sprinters.”

The researchers didn’t test Bolt in the SMU lab. Instead, they used a new motion-based method to assess the patterns of ground-force application. They analyzed Bolt and other elite runners using existing high-speed race footage available from NBC Universal Sports. The runners were competing in the 2011 Diamond League race at the World Athletics Championships in Monaco.

Udofa analyzed 20 of Bolt’s steps from the Monaco race, averaging data from 10 left and 10 right.

The researchers relied upon foot-ground contact time, aerial time, running velocity and body mass to determine the ground reaction forces using the new method, made possible by the “two-mass model” of running mechanics.

Runners typically run on a force-instrumented treadmill or force plates for research examining running ground-reaction forces. However, the two-mass model method provides a tool that enables motion-based assessments of ground reaction forces without direct force measurements.

“There are new avenues of research the model may make possible because direct-force measurements are not required,” Weyand said. “These include investigations of the importance of symmetry for sprinting performance. The two-mass model may facilitate the acquisition of data from outside the lab to help us better address these kinds of questions.”

Udofa presented the findings at the 35th International Conference on Biomechanics in Sport in Cologne, Germany. His presentation, “Ground Reaction Forces During Competitive Track Events: A Motion Based Assessment Method,” was delivered June 18.

Two-mass model relies on basic motion data
SMU researchers developed the concise two-mass model as a simplified way to predict the entire pattern of force on the ground — from impact to toe-off — with very basic motion data.

The model integrates classic physics and human anatomy to link the motion of individual runners to their patterns of force on the ground.

It provides accurate predictions of the ground force vs. time patterns throughout each instant of the contact period, regardless of limb mechanics, foot-strike type or running speed.

The two-mass model is substantially less complex than other scientific models that explain patterns of ground force application during running. Most existing models are more elaborate in relying on 14 or more variables, many of which are less clearly linked to the human body.

“The two-mass model provides us with a new tool for assessing the crucial early portion of foot-ground contact that is so important for sprinting performance,” said Udofa. “The model advances our ability to assess the impact-phase force and time relationships from motion data only.”

The two-mass model was developed in SMU’s Locomotor Performance Laboratory by Kenneth P. Clark, now an assistant professor in the Department of Kinesiology at West Chester University, West Chester, Pa.; Ryan, a physicist and research engineer at SMU’s Locomotor Performance Laboratory; and Weyand.

The researchers described the two-mass model earlier this year in the Journal of Experimental Biology in their article, “A general relationship links gait mechanics and running ground reaction forces.” It’s available at bitly, http://bit.ly/2jKUCSq.

Support for the research came from the U.S. Army Medical Research and Materiel Command.

Weyand is Glenn Simmons Professor of Applied Physiology and professor of biomechanics in the Department of Applied Physiology & Wellness in SMU’s Annette Caldwell Simmons School of Education & Human Development. — Margaret Allen, SMU