Research: The speed secrets of super sprinters

Peter Weyand

Research: The speed secrets of super sprinters

The world’s fastest sprinters have unique gait features that account for their ability to achieve fast speeds, according to two new studies from SMU’s Annette Caldwell Simmons School of Education and Human Development.

The new findings indicate that the secret to elite sprinting speeds lies in the distinct limb dynamics sprinters use to elevate ground forces upon foot-ground impact.

“Our new studies show that these elite sprinters don’t use their legs to just bounce off the ground as most other runners do,” said human biomechanics expert Ken Clark, a researcher in the SMU Locomotor Performance Laboratory and lead author on the studies. “The top sprinters have developed a wind-up and delivery mechanism to augment impact forces. Other runners do not do so.”

The new findings address a major performance question that has remained unanswered for more than a decade. Previous studies had established that faster runners attain faster speeds by hitting the ground more forcefully than other runners do in relation to their body weight. However, how faster runners are able to do this was fully unknown. That sparked considerable debate and uncertainty about the best strategies for athletes to enhance ground-force application and speed.

“Elite speed athletes have a running pattern that is distinct,” Clark said. “Our data indicate the fastest sprinters each have identified the same solution for maximizing speed, which strongly implies that when you put the physics and the biology together, there’s only one way to sprint really fast.”

The critical and distinctive gait features identified by the study’s authors occur as the lower limb approaches and impacts the ground, said study co-author and running mechanics expert Peter Weyand, director of the Locomotor Performance Lab.

“We found that the fastest athletes all do the same thing to apply the greater forces needed to attain faster speeds,” Weyand said. “They cock the knee high before driving the foot into the ground, while maintaining a stiff ankle. These actions elevate ground forces by stopping the lower leg abruptly upon impact.”

The new research indicates that the fastest runners decelerate their foot and ankle in just over two-hundredths of a second after initial contact with the ground.

The findings are reported in the Journal of Applied Physiology in the article, “Are running speeds maximized with simple-spring stance mechanics?” It appears online at Physiology.org in advance of appearing in the print journal.

Written by Margaret Allen

> Read the full story at the SMU Research blog

September 18, 2014|Faculty in the News, Research, Year of the Faculty|

Faculty in the News: March 8, 2011

Jake Batsell on CBS-11 NewsJake Batsell, Journalism, Meadows School of the Arts, provided expertise for a CBS-11 News story on tweeting and sports that was broadcast March 6, 2011. Watch Jake Batsell on CBS-11. video

Ed Fox, JCPenney Center for Retail Excellence, Cox School of Business, talked about the possible effects of rising commodity prices on Dallas-area consumers with The Dallas Morning News Feb. 22, 2011.

Bud Weinstein, Maguire Energy Institute, wrote that the current turmoil in the Middle East should be taken as a sign the United States should develop and maintain a complete portfolio of domestic energy sources in an article that appeared in The Hill Feb. 22, 2011. He also wrote about the potential of natural gas locked in shale formations in a story published by The Washington Examiner Feb. 18, 2011. In addition, he wrote about this resource’s potential impact on the Texas economy in a Fort Worth Star-Telegram article published Feb. 28, 2011.

Cal Jillson, Political Science, Dedman College, talked about the political implications of Texas’ changing demographics with The Houston Chronicle Feb. 18, 2011, and with The New York Times Feb. 25, 2011. He also discussed with The Canadian Press the political fallout from President Obama’s instruction to the U.S. Department of Justice to stop defending the Defense of Marriage Act, which prohibits same-sex marriage. The article was published Feb. 28, 2011, and appeared on numerous Canadian news sites.

Peter Weyand, Applied Physiology and Wellness, Annette Caldwell Simmons School of Education and Human Development, provided expertise for a story about how fast humans may eventually be able to run that appeared on National Public Radio Feb. 19, 2011.

Linda Eads, Dedman School of Law, talked about Texas lawyers’ vote against proposed amendments to the state bar’s Disciplinary Rules of Professional Conduct with Texas Lawyer Feb. 17, 2011.

John Attanasio, Dean, Dedman School of Law, provided expertise for a National Law Journal story on the successes of an SMU program that pays law firms to “test drive” new Law School graduates. The article appeared in the Feb. 28, 2011 edition.

March 8, 2011|Faculty in the News|

Research Spotlight: How much energy does it take to walk?

Stock photo of family walking through woodsAny parent that takes their kid out for a walk knows that children tire more quickly than adults – but why is that? Do kids and small adults walk differently from taller people, or do they tire faster for some other reason?

SMU researcher Peter Weyand is fascinated by the effect that body size has on physiological function. To find answers, he has teamed up with Maurice Puyau and Nancy Butte, from the USDA/ARS Children’s Nutrition Research Center at Baylor College of Medicine, and undergraduate Bethany Smith.

Together they decided to measure the metabolic rates of children and adults, ranging from 5 to 32 years old, weighing between 15.9 kilograms and 88.7 kilograms and ranging in height from 1.07 meters to 1.83 meters, to try to find out why larger people are more economical walkers than smaller people.

Weyand and his colleagues publish their discovery that walkers of all heights use the same amount of energy per stride, making short people less economical because they take more steps. They also derive a fundamental equation to calculate exactly how much energy walkers use with direct applications in all walks of life.

The team published its discovery in the article “The mass-specific energy cost of human walking is set by stature” in the current issue of The Journal of Experimental Biology.

First Weyand and colleagues filmed male and female volunteers as they walked on a treadmill at speeds ranging from a slow 0.4 meters per second up to 1.9 meters per second. Meanwhile, they simultaneously measured the walkers’ oxygen consumption and carbon dioxide production rates to obtain their total metabolic rate.

Next the team calculated the amount of energy that each person used for walking by subtracting the basal metabolic rate (energy required to maintain the body’s basic metabolic functions) from the total metabolic rate measured while walking.

Finally, the team compared the way each person walked, measuring the walkers’ stride lengths, stride durations and the proportion of each stride they spent in contact with the ground (duty factor) to find out if large and small people walk differently.

Analysing the walkers’ styles, the team found that all of them moved in exactly the same way regardless of their height. Essentially, if you scaled a 5-year-old up to 2 meters, the giant child would walk in exactly the same way as a 2-meter-tall adult. So large people are not more economical because they walk differently from smaller people.

Next the team calculated the metabolic cost of a stride as each walker moved at their most economical pace and they discovered that walkers use the same amount of energy per stride regardless of their height. So, big people do not become more economical because they walk in a more economical style. Something else must account for their increased economy.

Finally, the four scientists plotted the walkers’ heights against their minimum energy expenditure and they were amazed when they got a straight line with a gradient of almost -1. The walkers’ energy costs were inversely proportional to their heights, with tall people walking more economically than short/smaller people because they have longer strides and have to take fewer steps to cover the same distance. So smaller people tire faster because each step costs the same and they have to take more steps to cover the same distance or travel at the same speed.

Peter Weyand and Oscar PistoriusBased on this discovery the group derived an equation that can be used to calculate the energetic cost of walking.

“The equation allows you to use your height, weight and distance walked to determine how many calories you burn,” says Weyand (at left in photo), associate professor of applied physiology and biomechanics in SMU’s Annette Caldwell Simmons School of Education and Human Development.

The equation could also be built into popular pedometers to provide users with a more realistic idea of how many calories they expend walking throughout the day. Finally, the team is keen to extend the equation to calculate metabolic costs at any speed.

“This has clinical applications, weight balance applications and the military is interested too because metabolic rates influence the physiological status of soldiers in the field,” explains Weyand.

Written by Kathryn Knight, The Company of Biologists

> Read more from the SMU Research blog

November 30, 2010|Research|

Faculty in the News: April 27, 2010

Jasper Smits, Psychology, Dedman College, discussed his research on how exercise can help get rid of anxiety with USA Today April 26, 2010.

Peter Weyand, Applied Physiology and Wellness, Annette Caldwell Simmons School of Education and Human Development, discussed the recent selection of single-amputee distance runner Amy Palmiero-Winters to the U.S. track team for an article that appeared in USA Today April 26, 2010.

Mary Spector, Dedman School of Law, talked about issues that arise when debt-collection companies use litigation to collect past-due bills for an article that appeared in The New York Times April 22, 2010.

Cal Jillson, Political Science, Dedman College, talked about civil-rights ramifications in the case of a gay couple seeking a divorce in Texas with The Fort Worth Star-Telegram April 20, 2010. He also discussed the popularity – and speaking fees – of Sarah Palin with the Star-Telegram April 19, 2010.

Alan Bromberg, Dedman School of Law, talked about the U.S. Securities and Exchange Commission’s fraud suit against Goldman Sachs with CNN Money April 19, 2010.

Bernard Weinstein, Maguire Energy Institute, Cox School of Business, wrote about creating a nuclear renaissance by reprocessing nuclear fuel in The Fort Worth Star-Telegram April 17, 2010.

Brian Bruce, EnCap Investments & LCM Group Alternative Asset Management Center, Cox School of Business, discussed how volatile markets have pushed some to invest in gold and jewels for an article published in The Chicago Tribune April 14, 2010.

David Meltzer, Anthropology, Dedman College, and Vance Holliday of the University of Arizona discussed how Paleoindians coped with climate change 11,000 years ago with Science News April 12, 2010.

Stan Wojewodski, Theatre, Meadows School of the Arts, discussed his career and his work with Dallas’ Undermain Theatre as part of a profile that appeared in The Dallas Morning News April 10, 2010. He becomes chair of the Meadows Division of Theatre in Fall 2010.

Carolyn Macartney, Cinema-TV, Meadows School of the Arts, discussed her upcoming film about the life of her grandmother – a former Wild West sharpshooter who was billed as Wanda Savage – with The Dallas Morning News April 9, 2010.

April 27, 2010|Faculty in the News|

Research Spotlight: Breaking the human speed limit

SMU sprinter Ebony CuingtonJamaican sprinter Usain Bolt‘s record-setting performances have unleashed a wave of interest in the ultimate limits to human running speed. A new study published Jan. 21, 2010, in the Journal of Applied Physiology offers intriguing insights into the biology and perhaps even the future of human running speed.

The newly published evidence identifies the critical variable imposing the biological limit to running speed, and offers an enticing view of how the biological limits might be pushed back beyond the nearly 28 miles per hour speeds achieved by Bolt to speeds of perhaps 35 or even 40 miles per hour.

The new paper, “The biological limits to running speed are imposed from the ground up,” was authored by Peter Weyand of SMU; Rosalind Sandell and Danille Prime, both formerly of Rice University; and Matthew Bundle of the University of Wyoming.

“The prevailing view that speed is limited by the force with which the limbs can strike the running surface is an eminently reasonable one,” says Weyand, associate professor of applied physiology and biomechanics in the Annette Caldwell Simmons School of Education and Human Development.

“If one considers that elite sprinters can apply peak forces of 800 to 1,000 pounds with a single limb during each sprinting step, it’s easy to believe that runners are probably operating at or near the force limits of their muscles and limbs,” he says. “However, our new data clearly show that this is not the case. Despite how large the running forces can be, we found that the limbs are capable of applying much greater ground forces than those present during top-speed forward running.”

The researchers found that the critical biological limit is actually imposed by time – specifically, the very brief periods of time available to apply force to the ground while sprinting. In elite sprinters, foot-ground contact times are less than one-tenth of one second, and peak ground forces occur within less than one-twentieth of one second of the first instant of foot-ground contact.

The researchers used a high-speed treadmill capable of attaining speeds greater than 40 miles per hour and of acquiring precise measurements of the forces applied to the surface with each footfall. They also had subjects perform at high speeds in different gaits. In addition to completing traditional top-speed forward running tests, subjects hopped on one leg and ran backward to their fastest possible speeds on the treadmill.

The unconventional tests were selected to examine the prevailing belief that human running speed is limited by how forcefully a runner’s limbs can strike the ground. However, the researchers found that the ground forces applied while hopping on one leg at top speed exceeded those applied during top-speed forward running by 30 percent or more, and that the forces generated by the active muscles within the limb were roughly 1.5 to 2 times greater in the one-legged hopping gait.

The new work shows that running speed limits are set by the contractile speed limits of the muscle fibers themselves, with fiber contractile speeds setting the limit on how quickly the runner’s limb can apply force to the running surface, the researchers say.

Read more and review international press coverage at the SMU Research blog

(Above, sophomore sprinter Ebony Cuington of SMU’s track and field team.)

January 26, 2010|Research|
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