Category: Feature

Categories
Culture, Society & Family Feature Health & Medicine Student researchers

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

Categories
Culture, Society & Family Feature Fossils & Ruins Researcher news SMU In The News

Sapiens: Why the Famous Folsom Point Isn’t a Smoking Gun

A Folsom spear point was discovered between the ribs of an extinct species of bison — but was it really proof that humans had killed the animal?

A Folsom spear point was discovered between the ribs of an extinct species of bison — but was it really proof that humans had killed the animal?

The research into the arrival of how and when people first arrived in North America by noted SMU archaeologist David J. Meltzer was covered in the online anthropology magazine Sapiens in a column by Stephen E. Nash, science historian and archaeologist at the Denver Museum of Nature & Science.

The article, Why the Famous Folsom Point Isn’t a Smoking Gun, published Aug. 29, 2017.

Meltzer, a member of the National Academy of Sciences and Henderson-Morrison Professor of Prehistory in SMU’s Dedman College of Humanities and Sciences, conducts original research into the origins, antiquity and adaptations of the first Americans.

Paleoindians colonized the North American continent at the end of the Ice Age. Meltzer focuses on how those hunter-gatherers met the challenges of moving across and adapting to the vast, ecologically diverse landscape of Late Glacial North America during a time of significant climate change.

Meltzer’s archaeology and history research has been supported by grants from the National Geographic Society, the National Science Foundation, The Potts and Sibley Foundation and the Smithsonian Institution. In 1996, he received a research endowment from Joseph and Ruth Cramer to establish the Quest Archaeological Research Program at SMU, which will support in perpetuity research on the earliest occupants of North America.

Read the full story.

EXCERPT:

By Stephen E. Nash
Sapiens
Remember the iconic Folsom point? The one that I said, in my last post, changed the future of archaeology?

To recap: On August 29, 1927, paleontologists from the Colorado Museum of Natural History (renamed the Denver Museum of Nature & Science in 2000) discovered a stone projectile point embedded in the ribs of an extinct form of bison.

After making that discovery in the field, the researchers left the point sitting where it was and immediately sent out a call to their colleagues to come to northeastern New Mexico to see it for themselves. Within two weeks a number of well-known scientists had visited the site, seen the point in position, and established a scientific consensus: Native Americans lived and hunted in North America during the end of the last Ice Age, about 12,000 years ago, far earlier than they were previously thought to be here.

It turns out, though, that the story at the Folsom Site was more complicated than researchers initially believed. So what has changed since 1927? The latest part of the story began 20 years ago.

In 1997, David Meltzer, an archaeologist at Southern Methodist University who studies “Paleoindians,” the earliest inhabitants of North America, began a three-year project at the Folsom Site to reassess and re-excavate the site using modern tools and techniques—which were not available in the 1920s. His goal was to better understand how, and under what conditions, the Folsom Site formed. Meltzer and his team used now-standard excavation-control techniques to record their findings in three-dimensional space and to determine if any unexcavated areas of the site could be found. In so doing, they hoped to find evidence of the Paleoindian campsite that might have been associated with the main bison-kill and butchering site.

As a result of Meltzer’s research, we now know that the bison-kill event occurred in the fall. How do we know? Bison reproduce, give birth, and grow up on a reasonably predictable annual cycle. Meltzer and his colleagues analyzed dental eruption patterns on excavated bison teeth to determine the season of the kill.

The archaeologists also determined that Folsom hunters were experts at their job, having systematically killed and butchered at least 32 bison at the site.

Read the full story.

Categories
Earth & Climate Feature Fossils & Ruins Plants & Animals Researcher news

The mystery of leaf size solved by global team of scientists

A global team of researchers, including SMU paleobotanist Bonnie Jacobs, have cracked the mystery of leaf size. The research was published Sept. 1, 2017 as a cover story in Science.

SMU paleobotanist Bonnie F. Jacobs has contributed research to a major new study that provides scientists with a new tool for understanding both ancient and future climate by looking at the size of plant leaves.

Why is a banana leaf a million times bigger than a common heather leaf? Why are leaves generally much larger in tropical jungles than in temperate forests and deserts? The textbooks say it’s a balance between water availability and overheating.

But it’s not that simple, the researchers found.

The study, published in the Sept. 1, 2017 issue of Science, was led by Associate Professor Ian Wright from Macquarie University, Australia. The study’s findings reveal that in much of the world the key factor limiting the size of a plant’s leaves is the temperature at night and the risk of frost damage to leaves.

Jacobs said the implications of the study are significant for enabling scientists to either predict modern leaf size in the distant future, or to understand the climate for a locality as it may have been in the past.

“This research provides scientists with another tool for predicting future changes in vegetation, given climate change, and for describing ancient climate given fossil leaves,” said Jacobs, a professor in SMU’s Roy M. Huffington Department of Earth Sciences in the Dedman College of Humanities and Sciences.

“Now we can reliably use this as another way to look at future climate models for a specific location and predict the size of plant leaves,” she said. “Or, if we’re trying to understand what the climate was for a prehistoric site tens of millions of years ago, we can look at the plant fossils discovered in that location and describe what the climate most likely was at that time.”

Wright, Jacobs and 15 colleagues from Australia, the U.K., Canada, Argentina, the United States, Estonia, Spain and China analyzed leaves from more than 7,600 species, then pooled and analyzed the data with new theory to create a series of equations that can predict the maximum viable leaf size anywhere in the world based on the risk of daytime overheating and night-time freezing.

The researchers will use these findings to create more accurate vegetation models. This will be used by governments to predict how vegetation will change locally and globally under climate change, and to plan for adaptation.

Big data solves century-old conundrum
The iconic paintings of Henri Rousseau illustrate that when we think of steamy tropics we expect large leaves. But for scientists it’s been a century-old conundrum: why does leaf size vary with latitude – from very small near the poles to massive leaves in the tropics?

“The conventional explanation was that water availability and overheating were the two major limits to leaf size. But the data didn’t fit,” says Wright. “For example the tropics are both wet and hot, and leaves in cooler parts of the world are unlikely to overheat.”

“Our team worked both ends of the problem – observation and theory,” he says. “We used big data – measurements made on tens of thousands of leaves. By sampling across all continents, climate zones and plant types we were able to show that simple ‘rules’ seemingly operate across the world’s plant species, rules that were not apparent from previous, more limited analyses.”

Jacobs contributed an extensive leaf database she compiled about 20 years ago, funded by a National Science Foundation grant. She analyzed the leaf characteristics of 880 species of modern tropical African plants, which occurred in various combinations among 30 plant communities. Jacobs measured leaves of the plant specimens at the Missouri Botanical Garden Herbarium, one of the largest archives of pressed dried plant specimens from around the world.

She looked at all aspects of leaf shape and climate, ranging from seasonal and annual rainfall and temperature for each locale, as well as leaf shape, size, tip, base, among others. Using statistical analyses to plot the variables, she found the most prominent relationship between leaf shape and climate was that size increases with rainfall amount. Wet sites had species with larger leaves than dry sites.

Her Africa database was added to those of many other scientists who have compiled similar data for other localities around the world.

Threat of night time frost damage determines the size of a leaf
“Using our knowledge of plant function and biophysics we developed a fresh take on ‘leaf energy balance’ theory, and compared our predictions to observed leaf sizes,” Wright says.

“The most surprising result was that over much of the world the maximum size of leaves is set not by the risk of overheating, but rather by the risk of damaging frost at night. Larger leaves have thicker, insulating ‘boundary layers’ of still air that slows their ability to draw heat from their surroundings – heat that is needed to compensate for longwave energy lost to the night-time sky,” says co-author Colin Prentice from Imperial College London, who co-ordinated the mathematical modelling effort.

“International collaborations are making ecology into a predictive science at global scale,” says Emeritus Professor Mark Westoby. “At Macquarie University we’re proud to have led this networking over the past 20 years.” — Margaret Allen, SMU, and Macquarie University

By Ian Wright
Macquarie University
As a plant ecologist, I try to understand variation in plant traits (the physical, chemical and physiological properties of their tissues) and how this variation affects plant function in different ecosystems.

For this study I worked with 16 colleagues from Australia, the UK, Canada, Argentina, the US, Estonia, Spain and China to analyse leaves from more than 7,600 species. We then teamed the data with new theory to create a model that can predict the maximum viable leaf size anywhere in the world, based on the dual risks of daytime overheating and night-time freezing.

These findings will be used to improve global vegetation models, which are used to predict how vegetation will change under climate change, and also to better understand past climates from leaf fossils.

From giants to dwarfs
The world’s plant species vary enormously in the typical size of their leaves; from 1 square millimetre in desert species such as common eutaxia (Eutaxia microphylla), or in common heather (Calluna vulgaris) in Europe, to as much as 1 square metre in tropical species like Musa textilis, the Filipino banana tree.

But what is the physiological or ecological significance of all this variation in leaf size? How does it affect the way that plants “do business”, using leaves as protein-rich factories that trade water (transpiration) for carbon (photosynthesis), powered by energy from the sun?

More than a century ago, early plant ecologists such as Eugenius Warming argued that it was the high rainfall in the tropics that allowed large-leaved species to flourish there.

In the 1960s and ‘70s physicists and physiologists tackled the problem, showing that in mid-summer large leaves are more prone to overheating, requiring higher rates of “transpirational cooling” (a process akin to sweating) to avoid damage. This explained why many desert species have small leaves, and why species growing in cool, shaded understoreys (below the tree canopy) can have large leaves.

But still there were missing pieces to this puzzle. For example, the tropics are both wet and hot, and these theories predicted disadvantages for large-leafed species in hot regions. And, in any case, overheating must surely be unlikely for leaves in many cooler parts of the world.

Our research aimed to find these missing pieces. By collecting samples from all continents, climate zones and plant types, our team found simple “rules” that appear to apply to all of the world’s plant species – rules that were not apparent from previous, more limited analyses.

We found the key factors are day and night temperatures, rainfall and solar radiation (largely determined by distance from the Equator and the amount of cloud cover). The interaction of these factors means that in hot and sunny regions that are also very dry, most species have small leaves, but in hot or sunny regions that receive high rainfall, many species have large leaves. Finally, in very cold regions (e.g. at high elevation, or at high northern latitudes), most species have small leaves.

But the most surprising results emerged from teaming the new theory for leaf size, leaf temperature and water use with the global data analyses, to investigate what sets the maximum size of leaves possible at any point on the globe.

Read the author’s full essay

Categories
Culture, Society & Family Feature Health & Medicine Learning & Education Researcher news SMU In The News

Sapiens: Can Medical Anthropology Solve the Diabetes Dilemma?

As the number of sufferers continues to rise, some researchers are moving in new directions to figure out how culture and lifestyle shape disease outcomes.

Sapiens reporter Kate Ruder covered the research of SMU anthropologist Carolyn Smith-Morris, who has studied diabetes among Arizona’s Pima Indians for more than 15 years.

Smith-Morris wrote about what she learned from her research in her 2006 book, “Diabetes Among the Pima: Stories of Survival.”

The Pima have the highest prevalence of diabetes ever recorded, although the disease is alarmingly on the increase throughout the United States. In an effort to understand the rise of the disease, the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) from 1965 to 2007 focused on the Pima to carry out the largest continuous study of diabetes in Native Americans. Researchers examined the environmental and genetic triggers of the disorder, management of the disease, and the treatment of thousands of Pimas.

Smith-Morris is a medical anthropologist and associate professor in the SMU Anthropology Department in Dedman College. Her research addresses chronic disease, particularly diabetes, through ethnographic and mixed methodologies. She has conducted ethnographic research among the Gila River (Akimel O’odham) Indian Community of Southern Arizona, Mexicans and Mexican immigrants to the U.S. and veterans with spinal cord injuries.

The Sapiens article, “Can Medical Anthropology Solve the Diabetes Dilemma?” published Aug. 22, 2017.

Read the full story.

EXCERPT:

By Kate Ruder
Sapiens
Mary (a pseudonym) was 18 years old and halfway through her second pregnancy when anthropologist Carolyn Smith-Morris met her 10 years ago. Mary, a Pima Indian, was living with her boyfriend, brother, parents, and 9-month-old baby in southern Arizona. She had been diagnosed with gestational diabetes during both of her pregnancies, but she didn’t consider herself diabetic because her diabetes had gone away after her first birth. Perhaps her diagnosis was even a mistake, she felt. Mary often missed her prenatal appointments, because she didn’t have a ride to the hospital from her remote home on the reservation. She considered diabetes testing a “personal thing,” so she didn’t discuss it with her family.

As Smith-Morris’ research revealed, Mary’s story was not unique among Pima women. Many had diabetes, but they didn’t understand the risks. These women’s narratives have helped to explain, in part, why diabetes has been so prevalent in this corner of the world. An astonishing half of all adult Pimas have diabetes.

Medical anthropologists like Smith-Morris are helping the biomedical community untangle the social roots of diabetes and understand how and why the disease is exploding in the United States. Smith-Morris, based out of Southern Methodist University in Dallas, Texas, has been working on this cause for over 15 years—from a decade spent among the Pimas, to a new study sponsored by Google aiming to prevent diabetes-related blindness. Anthropology, she says, provides the most holistic perspective of this complex problem: “Anthropology seems to me the only discipline that allows you to look both closely at disease … and from the bird’s eye perspective.”

More than 30 million people in the United States are estimated to have diabetes, and it’s on the rise. If trends continue, 1 out of every 3 American adults could have diabetes by 2050, according to the Centers for Disease Control and Prevention.

The condition involves insulin, a hormone that regulates the way the body uses food for energy. In type 1 diabetes, the body stops making insulin entirely; those affected need daily insulin injections to survive. In type 2 diabetes, which accounts for the vast majority of cases, change is more gradual.The body slowly makes less insulin and becomes less sensitive to it over the years. Gestational diabetes, which strikes during pregnancy, can give mothers a dangerous condition called preeclampsia, which is related to high blood pressure and can harm both mothers and babies. Women with gestational diabetes are more than seven times likelier to later develop type 2 diabetes than women who do not have the condition in pregnancy, and their children are at higher risk of obesity and diabetes. If left untreated, diabetes can cause heart disease, kidney failure, foot problems that can lead to amputation, and blindness.

The preventative measures for type 2 and gestational diabetes are seemingly straightforward: eat healthy foods, lose weight, and exercise. Treatment for both can include taking medications. Yet prevention, lifestyle, and treatment cannot entirely solve the problem; family history, ethnicity, and other factors play a critical role in a person’s susceptibility to type 2 and gestational diabetes. Both forms of diabetes continue to plague Americans, particularly certain groups, including Native Americans. “My interest in diabetes grew out of an interest in Indigenous groups,” says Smith-Morris. “I took on diabetes because it was important to them.”

From 1965 to 2007, the Pimas of Arizona were the focus of the largest continuous study of diabetes in Native Americans. Conducted by researchers from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), it examined the environmental and genetic triggers of the disorder, management of the disease, and the treatment of thousands of Pimas. It also documented that they had the highest prevalence of diabetes ever recorded. The pivotal work told researchers much of what they know about diabetes today, including that obesity is a significant risk factor, and that a mother’s diabetes during pregnancy can pass risk along to her children.

The political and economic contributors to the Pima people’s health problems have long been well-known: Their traditional farming practices collapsed during the late 1800s and early 1900s when non-Native settlers upstream diverted essential water resources, contributing to poverty, sedentariness, and a lack of fresh food. Yet Smith-Morris felt something integral was missing from this picture: the Pimas’ stories.

Read the full story.

Categories
Culture, Society & Family Earth & Climate Events Feature Learning & Education Slideshows SMU In The News Videos

A Total Eclipse of the First Day of School

Hundreds of students, faculty and townspeople gathered in the rotunda of Dallas Hall on Monday, Aug. 21 to view a projection of the Great American Solar Eclipse at a viewing hosted by Dedman College and the SMU Physics Department. (Jeff McWhorter/SMU)

Dedman College, SMU Physics Department host Great American Solar Eclipse 2017 viewing

Thousands of students, faculty and townspeople showed up to campus Monday, Aug. 21 to observe the Great American Solar Eclipse at a viewing hosted by Dedman College of Humanities and Sciences and the SMU Department of Physics.

The festive event coincided with the kick-off of SMU’s Fall Semester and included Solar Eclipse Cookies served while viewing the rare astronomical phenomenon.

The eclipse reached its peak at 1:09 p.m. in Dallas at more than 75% of totality.

“What a great first day of the semester and terrific event to bring everyone together with the help of Dedman College scientists,” said Dedman Dean Thomas DiPiero. “And the eclipse cookies weren’t bad, either.”

Physics faculty provided indirect methods for observing the eclipse, including a telescope with a viewing cone on the steps of historic Dallas Hall, a projection of the eclipse onto a screen into Dallas Hall, and a variety of homemade hand-held devices.

Outside on the steps of Dallas Hall, Associate Professor Stephen Sekula manned his home-built viewing tunnel attached to a telescope for people to indirectly view the eclipse.

“I was overwhelmed by the incredible response of the students, faculty and community,” Sekula said. “The people who flocked to Dallas Hall were energized and engaged. It moved me that they were so interested in — and, in some cases, had their perspective on the universe altered by — a partial eclipse of the sun by the moon.”

A team of Physics Department faculty assembled components to use a mirror to project the eclipse from a telescope on the steps of Dallas Hall into the rotunda onto a screen hanging from the second-floor balcony.

Adjunct Professor John Cotton built the mount for the mirror — with a spare, just in case — and Professor and Department Chairman Ryszard Stroynowski and Sekula arranged the tripod setup and tested the equipment.

Stroynowski also projected an illustration of the Earth, the moon and the sun onto the wall of the rotunda to help people visualize movement and location of those cosmic bodies during the solar eclipse.

Professor Fred Olness handed out cardboard projectors and showed people how to use them to indirectly view the eclipse.

“The turn-out was fantastic,” Olness said. “Many families with children participated, and we distributed cardboard with pinholes so they could project the eclipse onto the sidewalk. It was rewarding that they were enthused by the science.”

Stroynowski, Sekula and others at the viewing event were interviewed by CBS 11 TV journalist Robert Flagg.

Physics Professor Thomas Coan and Guillermo Vasquez, SMU Linux and research computing support specialist, put together a sequence of photos they took during the day from Fondren Science Building.

“The experience of bringing faculty, students and even some out-of-campus community members together by sharing goggles, cameras, and now pictures of one of the great natural events, was extremely gratifying,” Vasquez said.

Sekula said the enthusiastic response from the public is driving plans to prepare for the next event of this kind.

“I’m really excited to share with SMU and Dallas in a total eclipse of the sun on April 8, 2024,” he said.