Shhh … I’m Hibernating!

Bear nest

Man crawling out of uninhabited bear hibernating den (not recommended). Credit: IStock

As the days grow shorter, many animals, such as bats, bears and bees, begin getting ready to hibernate. It’s a process that allows animals to spend the winter months conserving energy by reducing metabolism, oxygen consumption and body temperature. So why don’t humans do it, too? Well, a new study suggests that some humans—specifically those with chronic fatigue syndrome (CFS), which affects more than 2.5 million people in the U.S.—may be doing something similar to hibernating.

People with chronic fatigue syndrome experience extreme fatigue. But this is not your run-of-the-mill kind of post-holiday exhaustion. It is severe fatigue that does not get better, even with sleep. People with CFS may also experience issues related to memory and headaches. It’s not clear why people develop the disorder, but some theories point to infections, exposure to chemicals or stress as possible causes.

The new study, published in the Proceedings of the National Academies of Science, looked at specific molecules (metabolites) that are byproducts of energy production (metabolism) in the blood of people who have CFS and healthy people who do not have the disease. The researchers found that people with the condition had 80 percent fewer metabolites compared to the healthy control subjects. Those with chronic fatigue syndrome also had some impairment in the way their metabolism functioned. The findings suggest a less active metabolism in people with CFS similar to metabolic activity seen in animals that hibernate. Reduction in metabolic state is thought to be a defensive strategy all humans can use to cope with situations in which environmental or other stressors are present. The problem for people with CFS is that this defense mechanism stays turned on, slowing metabolism—and draining energy—on an ongoing basis.

What’s great about this study is that researchers and clinicians finally have a set of chemical markers in the blood that they can use to test people for CFS. The hope is that by understanding what’s going wrong, metabolically speaking, a treatment can be developed.

Karen SweazeaKaren Sweazea, PhD, is an associate professor in the School of Nutrition & Health Promotion and the School of Life Sciences at Arizona State University.

What Happens during Heat Stroke and How to Prevent It


Young kids are at increased risk of heat stroke. Credit: IStock

Temperatures in July and August 2016 were the hottest ever recorded on the planet and much of the U.S. is still struggling with a heat wave. Hundreds of heat-related deaths occur in the U.S. each year, and these rates are on the rise. Awareness of when the body is losing the ability to deal with heat and seeking treatment for heat illness and dehydration are key to reducing heat stroke-related deaths. So it’s extremely important to understand the causes and symptoms of heat illnesses, such as heat stroke, and who’s at risk.

Under normal physiologic conditions, the human body can counteract overheating by sweating and other means. Heat illness occurs when the body is overwhelmed by the heat and can no longer maintain its temperature. Heat stroke is the most dangerous type of heat illness, though heat fatigue, heat cramps and heat exhaustion can also occur. These conditions can have a variety of effects on the body, blood flow and a person’s mental capacity. For example, heat stress with mild to moderate dehydration can result in loss of blood flow to the brain and the inability to stay upright.

Who’s at Risk of Heat Stroke and How to Prevent It

Heat stroke can develop in people of any age or health status, but the sedentary elderly, very young people and individuals with chronic disease such as heart disease have a significantly higher risk of having one. People who take certain medications, drink alcohol, are very overweight or who have poor blood circulation (such as those with diabetes and heart disease) or reduced sweat production due to aging are also at an increased risk. Prolonged, intense exercise in a hot environment without proper hydration can cause a heat stroke during heat waves, even among young and healthy people.

The most effective ways to prevent heat stroke is to ensure that high-risk populations:

  • have access to air conditioning or a cool environment with air flow;
  • dress comfortably in layers that can be removed as the temperature rises;
  • stay hydrated by consuming water, fruits and vegetables (such as watermelon, tomatoes, lettuce, pineapple, cranberries and oranges), herbal tea, etc; and
  • understand the signs and symptoms of heat stroke.

People may be developing heat illness if they appear confused or faint, are not sweating or have flushed skin after being exposed to the heat. Any individual experiencing these symptoms should be removed from the heat, offered fluids and examined for the possibility of heat illness or heat stroke.


Robert Carter, III, PhD, MPH, FACSM, is an adjunct professor of emergency medicine at the University of Texas Health Science Center at San Antonio and the product manager for medical simulation at the Program Executive Office for Simulation, Training and Instrumentation in Orlando.

What Is Physiology?…and Why You Should Care


Credit: IStock

Physiology provides an explanation of life, and everyone—not just doctors and scientists—would benefit from understanding some essential physiological concepts. But to learn how physiology applies to everyday life, you must first understand what it is.

Physiology is the study of how living organisms function in sickness and in health. Physiologists study functions that may take place on a small scale, such as in molecules or individual cells, or in whole animals such as humans. Physiological research has led to breakthroughs in our understanding of how we move, reproduce, gain and lose weight, live, thrive, die and much more. Because of this, a strong grasp of physiology is imperative for doctors and other health care providers who see patients and treat disease.

But it’s also important for the average person to have an understanding of physiology. It can help patients understand why their doctor recommends that they work out, eat less salt or take a certain medicine. Physiology can also inform our everyday decisions related to diet, exercise and sleep.

Integrative physiologists, like me, study how the body responds to stimuli such as exercise. Some examples of the type of functions we study include:

  • How oxygen supports metabolism, how its use determines how many calories we “burn” at rest and during exercise and how it can help determine a person’s cardiorespiratory fitness level.
  • How the body controls blood pressure, what happens to blood pressure when we exercise, and what can be done to lower blood pressure and prevent it from getting too high.
  • The critical role of sodium (salt) in regulating fluid levels in the body and how it can raise blood pressure and damage tissues when too much is consumed.
  • The importance of blood flow regulation in delivering nutrients and oxygen to the working muscles at rest and during exercise, which is critical for athletes and for slowing down age-related declines in physical function.

Key physiology concepts provide the framework for addressing these issues, and there is still so much to learn and explore!

To quote one of physiology’s forefathers, Arthur C. Guyton, “Physiology is indeed an explanation of life. What other subject matter is more fascinating, more exciting, more beautiful than the subject of life?” I agree (though I may be biased). But whether you’re intrigued by physiology or not, the insights into health and disease that it uncovers hold a benefit for us all.

william-farquharWilliam B. Farquhar, PhD, is a professor and chair in the department of kinesiology and applied physiology at the University of Delaware. He is a Fellow of the American College of Sports Medicine and member of the American Physiological Society.

A 10,000-Foot View from the ALMA Observatory in Atacama

Atacama Telescope

Rare clouds drift behind a telescope at the ALMA Observatory in Chile.

After fulfilling the main purpose of our trip—to build relationships with universities in Santiago, the capital city of Chile—we headed north to the Atacama Desert, the driest non-polar desert in the world.  The small town of San Pedro de Atacama serves as a starting point for adventure travelers looking to experience all this beautiful landscape has to offer. It is also the closest town to the Atacama Large Millimeter/submillimeter Array (ALMA)—a multi-national space observatory that seeks to understand our cosmic origins.

My colleagues and I boarded a public tour bus to the ALMA operations center. The on-board safety video once again put physiology front and center as it discussed a reality that locals here deal with every day: the effects of altitude on the human body.

San Pedro, and most of the Atacama Desert, is located at around 8,000 feet above sea level. The ALMA control center sits above the town at around 10,000 feet. Most impressively, the radio telescopes that make the observations are located on a plateau at 16,000 feet high. For comparison, Mount Whitney, the highest mountain in the continental U.S., is 14,505 feet above sea level.

UV Warning Atacama

A warning to ALMA visitors about prolonged UV exposure.

Spending time at high altitudes can have an impact on the cardiovascular and respiratory systems. The increased ultraviolet exposure is significant, and ALMA visitors (even just to the control center) are cautioned against spending prolonged periods in the sun and are advised to wear sunscreen and protective clothing. The extremely arid Atacama Desert also challenges the body’s ability to maintain proper hydration, so water is frequently provided to visitors.

The safety video explained that at 10,000 feet, the control center is considered “moderate” altitude that most people can tolerate well. However, we learned that any visitors to the actual telescopes—which the general public is not allowed to visit—must go through a medical screening that includes taking vital signs (heart rate, blood pressure, blood oxygenation) and assessing signs and symptoms of altitude sickness (dizziness, headaches, nausea). Telescope visitors must also spend a minimum of one night getting used to the high elevation (acclimatizing) in Calama (the town where the nearest airport is) or San Pedro to prepare the body for this challenging environment. They are also given supplemental oxygen to help prevent any altitude-related issues and to allow them to perform physical tasks that might otherwise be too difficult.

All of these physiological challenges of visiting and working at ALMA ultimately are what makes it perfectly suited for its main purpose, observing our skies. Dryness, high altitude, no clouds and minimal light or radio pollution from nearby sparsely populated towns (it’s not easy to live in the Atacama!) are perfect conditions for the ALMA scientists to try to solve important astronomical mysteries.

Anne Crecelius - Chile

Crecelius puts safety first during her visit to the ALMA Observatory.

This post is part two of a three-part series by physiologist Anne Crecelius, PhD, chronicling her summer of research and travels through South America. (Read part one here.) Crecelius is assistant professor at the University of Dayton.

Physiology for the Armchair Scientist


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Want to learn more about physiology without going back to school for a PhD? Check out The website, hosted by the American Physiological Society, goes in-depth to explain the multi-faceted field of physiology to nonscientists. In addition to examining hot and emerging areas of research such as brain physiology, obesity and exercise, we look at the how the body’s systems work individually and together to keep us going every day.

Our reference library houses quizzes that will test your physiology smarts, dozens of podcasts on cool research findings, a library of vintage equipment dating as far back as the 1870s and much more. We also feature timelines that highlight important milestones and people in the history of physiology.

We hope the site will serve as a helpful and informative resource about our area of research. Check back often for new information. And if you have questions you’d like us to address, let us know!

Stacy Brooks

If Only Birds Could Compete in the Summer Games

Frigatebird - Max Planck Ins

Frigatebird. Credit: Max Planck Institute.

Endurance is a hard-won characteristic of many elite athletes and is vital to winning most sporting competitions. If great frigatebirds could compete this summer, they would certainly take home a medal for endurance flight.

Frigatebirds are large sea birds with wingspans of more than six feet across. They are really good at gliding and can fly nonstop for weeks at a time. Researchers who study these birds suspected the birds got some shut-eye during these flights.

Recently,  Max Planck Institute for Ornithology researchers examined whether these birds are able to take naps while flying—yes, you read that right, while flying. To examine this, the team attached flight data recorders and measured brain activity of birds in flight.

The birds were awake and actively foraging during the day. However, at night the brain activity of the birds switched to a pattern that suggested they were taking short naps that were up to several minutes long while continuing to soar through the skies. In addition, they discovered that each hemisphere of their brain could take turns sleeping (i.e., unihemispheric sleep) or both sleep at the same time (i.e., bihemispheric sleep). Unihemispheric sleep allows the birds to stay partially alert to potential dangers,  watch where they are going and, of course, prevent themselves from falling from the sky.

This made me wonder how they prevent a crash landing when both sides of their brains take a nap. As it turns out, sleep duration for this deeper form of REM sleep only lasted a mere seconds and did not affect their flight pattern. Remarkably, these birds only average 42 minutes of sleep per day while out at sea. Researchers are still trying to figure out how they are able to function on such little sleep when they are known to sleep for more than 12 hours on land.

My thought is there must be a Starbucks in the sky.

Karen SweazeaKaren Sweazea, PhD, is an associate professor in the School of Nutrition & Health Promotion and the School of Life Sciences at Arizona State University.

In Santiago, What’s Smog Got to Do with It?


Smog hangs over the city of Santiago, Chile. Credit: Anne Crecelius

Upon arriving in Santiago, Chile, my travel companions from the University of Dayton and I were struck by the beautiful sights of the Andes mountains and the not-so-beautiful sight of a cloud of smog hanging over the city.

Like many major metropolitan areas, such as Los Angeles or Mexico City, the city of Santiago (population ~8 million) suffers from poor air quality. Typical contributors to pollution, such as dust and automobiles, are part of the problem, but Santiago also has a geological disadvantage. The city is located in a valley between the beautiful Andes mountains and the Pacific Coast, which often causes polluted air to “settle” in the city. Frequent thermal inversions—where cold air settles beneath warm air—amplify the smog problem, especially in the winter months (June through August in the Southern Hemisphere).

A recent study linked millions of deaths to air pollution in Asian countries. But what makes air pollution so bad for our bodies? Different pollutants can have different effects on each of the body’s systems. Depending on the size and amount of pollutants in the air, particles can irritate our lungs or even enter our bloodstream. Once in the blood, toxins can negatively affect multiple organs such as the lungs, heart, brain and liver.

So what are the residents of Santiago, or visitors like me, to do?

Keep Preexisting Conditions in Mind

People with existing conditions that affect the ability to breathe are at increased risk of problems caused by high smog levels. For example, my colleague who has asthma had to be extra careful and used her albuterol inhaler frequently. Albuterol is a medicine that acts on the passageways of the lungs to help them open and allow air to flow more easily.

Exercise with Caution

If air quality is exceptionally poor, such as during a thermal inversion, take extra caution when exercising outside, or consider indoor options.

Share the Road

Using public transportation, biking and walking can help reduce vehicle emissions. If you are around high-traffic areas, you still may want to cover your face to protect yourself from the larger particles in the air. While walking around the city, I observed many Chileans using this method.

My colleagues may not have taken notice, but I thought “I spy physiology!”

Anne Crecelius


This post is part one of a three-part series by physiologist Anne Crecelius, PhD, chronicling her summer of research and travels through South America. Crecelius is assistant professor at the University of Dayton.

Physiology Is Alive and Well, Just Ask an Undergraduate Student

Undergrad Poster Session at EB16

Physiology Undergraduate Poster Session at Experimental Biology 2016

When you think of a cutting-edge, exciting area of science, do you think of physiology? If not, you should. Physiology is the basis for medicine. Many important medical advances that we take for granted today are direct or indirect results of research conducted by physiologists. But despite the significance of our area of research, some universities are removing physiology from medical school curricula, shutting down physiology departments or calling them by another name. Not surprisingly, this causes a great deal of angst among physiologists and is often discussed in our community.

Luckily, physiology is flourishing at the undergraduate level. Despite a smorgasbord of options for college majors in life science disciplines—including bachelor of science degrees in genetics, biochemistry, cell and molecular biology, integrative biology, etc.—more universities have started to offer physiology as a stand-alone undergraduate major instead of  offering only a course on physiology. While the major has existed in a few isolated cases for many years (e.g., University of Arizona and Michigan State University), the past decade has seen many new programs added and the conversion of several programs from kinesiology to human physiology with 43 programs in the U.S. today. These programs typically have seen three- to five-fold increases in enrollment over the past five years.

Recently, we published a paper on the millennial student view of physiology. We found that:

  • 78 percent of physiology majors have preferences for studying whole-body physiology (with 67 percent interested in integrative/systems physiology and 11 percent interested in integrative and cellular physiology);
  • students interested in cell- and molecule-level function are gravitating to other majors such as biochemistry and genetics;
  • student interest in integrative physiology is aligned with
    • interest in an applied and holistic view of human health and disease and
    • student aspirations for careers in health care; and
  • physiology programs are the primary pathway for students heading into medicine, physical therapy and other allied health professions, with 85 to 90 percent of students in a physiology major stating career aspirations in health care.

Considering these findings, one thing seems clear: Millennial undergraduate students intuitively understand that physiology is the basis for medicine. They know that choosing a major in physiology is the best way to learn more about the human body. In my opinion, physiology is alive and well; you just have to know where to look.


Wehrwein_Erica 2009

Erica A. Wehrwein is an assistant professor at Michigan State University.  She leads the Physiology Majors Interest Groups (P-MIG), a consortium of physiology undergraduate programs.

Pop Quiz: Test Your Physiology Knowledge!

PIO Quiz Image

Take our physiology quizzes!

If you’ve been following along with the I Spy Physiology blog, you may be feeling like a physiology wiz. APS member-physiologists have developed a series of quizzes to help you test your physiology smarts and, perhaps, teach you something new. Visit to take one of our systems quizzes (cardiovascular, digestive, endocrine or respiratory) or check out our general physiology quizzes (part 1 and part 2) that test your knowledge of physiological functions throughout the body. Share the quizzes with your friends and colleagues to compare scores, and remember to check back often for new quizzes as they’re posted.

Happy quizzing!

Stacy Brooks

Not in the Same Vein

Human circulatory system, full figure, cutaway anatomy illustration.

Human circulatory system. Credit: IStock

The word “vein” pops up in a variety of contexts. When used as a figure of speech, vein means similar or alike, for example “in the same vein as.” But in the body, vein refers to a specific type of blood vessel.

Encyclopedia Britannica defines blood vessel as “a vessel in the human or animal body in which blood circulates.” Though they may be structurally similar to the two other types of blood vessels—arteries and capillaries—veins have a unique and important role in circulation.

When the heart contracts, it pumps out oxygen-rich blood that first passes through arteries, then into capillaries—the location where oxygen is sent out to the body and carbon dioxide and other waste is picked up. The deoxygenated blood then travels through the veins back to the heart. The whole process takes just 20 seconds to complete. (WATCH this cool real-time animation of the red blood cell cycle.)

While veins are primarily responsible for moving oxygen-depleted blood back to the heart, this is not always the case. The amount of oxygen in the blood carried in the veins varies depending on whether they service the lungs (as part of pulmonary circulation) or the rest of the body (as part of systemic circulation). In systemic circulation, arteries carry oxygenated blood to the organs, and muscles and veins carry deoxygenated blood back to the heart. In pulmonary circulation, the process is reversed. The arteries carry oxygen-poor blood to the lungs, while the veins deliver newly oxygenated blood to the heart.

Veins and arteries also look different. Arteries control blood flow and pressure, so they are muscular to narrow and widen (dilate) effectively. Veins are less muscular than arteries and have thin, stretchy walls, which is why you can see them bulge out of your arms and hands. Because the blood pressure in the veins is lower and the blood is often moving against gravity, most veins also have valves to ensure blood flows in only one direction.

So when it comes to blood vessels, differences in their look and function demonstrate that they are not in the same vein.

Maggie Kuo and Stacy Brooks