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Study: New simple method determines rate at which we burn calories walking uphill, downhill, and on level ground

New method uses three variables of speed, load carried and slope to improve on the accuracy of existing standards for predicting how much energy people require for walking — a method beneficial to many, including military strategists to model mission success

When military strategists plan a mission, one of many factors is the toll it takes on the Army’s foot soldiers.

A long march and heavy load drains energy. So military strategists are often concerned with the calories a soldier will burn, and the effect of metabolic stress on their overall physiological status, including body temperature, fuel needs and fatigue.

Now scientists at Southern Methodist University, Dallas, have discovered a new more accurate way to predict how much energy a soldier uses walking.

The method was developed with funding from the U.S. military. It significantly improves on two existing standards currently in use, and relies on just three readily available variables.

An accurate quantitative assessment tool is important because the rate at which people burn calories while walking can vary tenfold depending on how fast they walk, if they carry a load, and whether the walk is uphill, downhill or level.

“Our new method improves on the accuracy of the two leading standards that have been in use for nearly 50 years,” said exercise physiologist Lindsay W. Ludlow, an SMU post-doctoral fellow and lead author on the study. “Our model is fairly simple and improves predictions.”

The research is part of a larger load carriage initiative undertaken by the U.S. Army Medical Research and Materiel Command. The average load carried by light infantry foot soldiers in Afghanistan in April and May 2003 was 132 pounds, according to a U.S. Army Borden Institute report.

“Soldiers carry heavy loads, so quantitative information on the consequences of load is critical for many reasons, from planning a route to evaluating the likelihood of mission success,” said SMU biomechanist and physiologist Peter Weyand, @Dr_Weyand.

“The military uses a variety of approaches to model, predict and monitor foot-soldier status and performance, including having soldiers outfitted with wearable devices,” Weyand said. “There is a critical need with modern foot soldiers to understand performance from the perspective of how big a load they are carrying.”

Weyand is senior author on the research and directs the Locomotor Performance Laboratory in the SMU Simmons School of Education, where subjects for the study were tested.

The researchers call their new method the “Minimum Mechanics Model” to reflect that it requires only three basic and readily available inputs to deliver broad accurate predictions. They report their findings in “Walking economy is predictably determined by speed, grade and gravitational load” in the Journal of Applied Physiology.

The necessary variables are the walker’s speed, the grade or slope of the walking surface, and the total weight of the body plus any load the walker is carrying.

“That’s all it takes to accurately predict how much energy a walker burns,” Ludlow said.

While the measurement is a critical one for foot soldiers, it’s also useful for hikers, backpackers, mall-walkers and others who are calorie conscious and may rely on wearable electronic gadgets to track the calories they burn, she said.

Muscle and gait mechanics tightly coupled across speed, grade, load
Existing standards now in use rely on the same three variables, but differently, and with less accuracy and breadth.

The new theory is a departure from the prevailing view that the mechanics of walking are too complex to be both simple and accurate.

“Ultimately, we found that three remarkably simple mechanical variables can provide predictive accuracy across a broad range of conditions,” Ludlow said. “The accuracy achieved provides strong indirect evidence that the muscular activity determining calorie-burn rates during walking is tightly coupled to the speed, surface inclination and total weight terms in our model.”

By using two different sets of research subjects, the researchers independently evaluated their model’s ability to accurately predict the amount of energy burned.

“If muscle and gait mechanics were not tightly coupled across speed, grade and load, the level of predictive accuracy we achieved is unlikely,” Weyand said.

First generalized equation developed directly from a single, large database
The two existing equations that have been the working standards for nearly 50 years were necessarily based on just a few subjects and a limited number of data points.

One standard from the American College of Sports Medicine tested only speed and uphill grades, with its first formulation being based on data from only three individuals.

The other standard, commonly referred to as the Pandolf equation is used more frequently by the military and relies heavily on data from six soldiers combined with earlier experimental results.

In contrast, the generalized equation from SMU was derived from what is believed to be the largest database available for human walking metabolism.

The SMU study tested 32 adult subjects individually under 90 different speed-grade and load conditions on treadmills at the SMU Locomotor Performance Laboratory, @LocomotorLabSMU.

“The leading standardized equations included only level and uphill inclinations,” Weyand said. “We felt it was important to also provide downhill capabilities since soldiers in the field will encounter negative inclines as frequently as positive ones.”

Subjects fast prior to measuring their resting metabolic rates
Another key element of the SMU lab’s Minimum Mechanics Model is the quantitative treatment of resting metabolic rate.

“To obtain true resting metabolic rate, we had subjects fast for 8 to 12 hours prior to measuring their resting metabolic rates in the early morning,” Ludlow said. “Once at the lab, they laid down for an hour while the researchers measured their resting metabolic rate.”

In separate test sessions, the subjects walked on the treadmill for dozens of trials lasting five minutes each, wearing a mouthpiece and nose clip. In the last two minutes of each trial, the researchers measured steady-state rates of oxygen uptake to determine the rate at which each subject was burning energy.

Adults in one group of 20 subjects were each measured walking without a load at speeds of 0.4 meters per second, 0.7 meters per second, 1 meter per second, 1.3 meters per second and 1.6 meters per second on six different gradients: downhill grades of minus six degrees and minus three degrees; level ground; and uphill at inclines of three degrees, six degrees and nine degrees.

Adults in a second group of 20 were each tested at speeds of 0.6 meters per second, 1 meter per second and 1.4 meters per second on the same six gradients, but they carried loads that were 18 percent of body weight, and 31 percent of body weight.

Walking metabolic rates increased in proportion to increased load
As expected, walking metabolic rates increased in direct proportion to the increase in load, and largely in accordance with support force requirements across both speed and grade, said Weyand and Ludlow.

Weyand is Glenn Simmons Professor of Applied Physiology and professor of biomechanics in the Department of Applied Physiology and Wellness in SMU’s Annette Caldwell Simmons School of Education and Human Development. He also is lead scientist for the biomechanics and modeling portion of the Sub-2-Hour marathon project, an international research consortium based in the United Kingdom. — Margaret Allen, SMU

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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.

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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.

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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.

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LiveScience: Newfound dino looks like creepy love child of a turkey and ostrich

A new giant bird-like dinosaur discovered in China has been named for SMU paleontologist Louis L. Jacobs, Corythoraptor jacobsi, by the scientists who identified the new oviraptorid. (Credit: Zhao Chuang)

A new giant bird-like dinosaur discovered in China has been named for SMU paleontologist Louis L. Jacobs, Corythoraptor jacobsi, by the scientists who identified the new oviraptorid.

Live Science Senior Writer Laura Geggel covered the discovery of a new Cretaceous Period dinosaur from China that is named for paleontologist Louis L. Jacobs, an SMU professor in SMU’s Roy M. Huffington Department of Earth Sciences.

Jacobs mentored three of the authors on the article. First author on the paper was Junchang Lü, an SMU Ph.D. alum, with co-authors Yuong–Nam Lee and Yoshitsugu Kobayashi, both SMU Ph.D. alums.

The Live Science article, Newfound dino looks like creepy love child of a turkey and ostrich, published July 27, 2017. The dinosaur’s name, Corythoraptor jacobsi, translates to Jacobs’ helmeted thief.

The scientific article “High diversity of the Ganzhou Oviraptorid Fauna increased by a new “cassowary-like” crested species” was published July 27, 2017 in Nature’s online open access mega-journal of primary research Scientific Reports.

Jacobs in 2016 co-authored an analysis of the Cretaceous Period dinosaur Pawpawsaurus based on the first CT scans ever taken of the dinosaur’s skull.

He is president of SMU’s Institute for the Study of Earth and Man.

A world-renowned vertebrate paleontologist, Jacobs in 2012 was honored by the 7,200-member Science Teachers Association of Texas with their prestigious Skoog Cup for his significant contributions to advance quality science education. He joined SMU’s faculty in 1983.

Jacobs is the author of “Quest for the African Dinosaurs: Ancient Roots of the Modern World” (Villard Books and Johns Hopkins U. Press, 2000); “Lone Star Dinosaurs” (Texas A&M U. Press, 1999), which is the basis of a Texas dinosaur exhibit at the Fort Worth Museum of Science and History; “Cretaceous Airport” (ISEM, 1993); and more than 100 scientific papers and edited volumes.

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By Laura Geggel
Live Science
The newly identified oviraptorid dinosaur Corythoraptor jacobsi has a cassowary-like head crest, known as a casque.

A Chinese farmer has discovered the remains of a dinosaur that could have passed for the ostrich-like cassowary in its day, sporting the flightless bird’s head crest and long thunder thighs, indicating it could run quickly, just like its modern-day lookalike, a new study finds.

The newfound dinosaur’s 6-inch-tall (15 centimeters) head crest is uncannily similar to the cassowary’s headpiece, known as a casque, the researchers said. In fact, the crests have such similar shapes, the cassowary’s may provide clues about how the dinosaur used its crest more than 66 million years ago, they said.

The findings suggest that the dinosaur, which would have towered at 5.5 feet (1.6 meters), may have had a similar lifestyle to the modern cassowary bird (Casuarius unappendiculatus), which is native to Australia and New Guinea, the study’s lead researcher, Junchang Lü, a professor at the Institute of Geology, Chinese Academy of Geological Sciences, told Live Science in an email.

Researchers found the oviraptorid — a type of giant, bird-like dinosaur — in Ganzhou, a city in southern China, in 2013. The specimen was in remarkable shape: The paleontologists found an almost complete skeleton, including the skull and lower jaw, which helped them estimate that the creature was likely a young adult, or at least 8 years of age, when it died.

The long-necked and crested dinosaur lived from about 100 million to 66 million years ago during the late Cretaceous period, and likely used its clawed hands to hunt lizards and other small dinosaurs, Lü added.

The research team named the unique beast Corythoraptor jacobsi. Its genus name refers to the raptor’s cassowary-like crest, and the species name honors Louis Jacobs, a vertebrate paleontologist at Southern Methodist University who mentored three of the study’s researchers.

The researchers think the crest likely served the dinosaur in different ways, they said, including in display, communication and perhaps even as an indication of the dinosaur’s fitness during the mating season.

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