Winter officially begins next week with the winter solstice—the day of the year with the fewest hours of sunlight—on Dec. 21. With the cold weather and shorter days, you might be tempted to curl up under a blanket until the spring thaw. Whether you plan to hibernate or get outside to enjoy the chill, we’ve got some good reads about how our physiology responds to the cold weather.
Check out these throwback posts featuring cold weather tips to help you stay safe and healthy during the coldest months:
Have fun, be safe and take note of how your body adapts to the season!
– Stacy Brooks and Erica Roth
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 Sweazea, PhD, is an associate professor in the School of Nutrition & Health Promotion and the School of Life Sciences at Arizona State University.
Credit: iStock/Getty Images
Rapamycin, a drug used to prevent organ transplant rejection, may also turn back time—in dogs at least. A study is underway to see if rapamycin can delay aging in dogs, and the puppy-like energy of one canine participant, eight-year-old Bela, gives some hope that the drug might work. Rapamycin is one of several drugs prescribed to treat other conditions that are being studied for their potential to help humans grow old without the health problems of aging. These drugs are particularly promising because they are already being used by people and are well-tolerated by the body. Other drugs being investigated include:
- Metformin: Metformin is a commonly prescribed treatment for type 2 diabetes. The specifics of how it counteracts aging are still being debated, but the scientific community generally agrees that small doses of metformin can improve metabolic health, reduce cancer risk and lengthen lifespan. The Targeting/Taming Aging with Metformin study is currently underway to test if metformin has anti-aging effects in people, as it did in mice.
- Aspirin: Constant low-level inflammation is considered a hallmark sign of aging, so researchers wonder if anti-inflammatory drugs such as aspirin can help. Studies have found that lifelong use of aspirin lengthens the average lifespan of male mice but does not increase maximum lifespan. No effects have been seen in female mice. Other studies in mice have shown that aspirin can improve immune, metabolic and cardiovascular health. However, aspirin also prevents blood from clotting and irritates the intestines, which can increase the risk of internal bleeding.
Researchers are also looking at lifestyle choices for their fountain-of-youth benefits, including:
- Vegan diet: A vegan diet reduces the consumption of methionine, a nutrient abundant in eggs and meat. Eating less methionine has been shown to increase the lifespan of yeast, worms, flies and rodents. However, methionine is an essential nutrient for the body, so its anti-aging properties may be counteracted by the health effects of not having enough of it.
- Calorie restriction: Reduced-calorie diets are a well-established method for extending the lifespan in various species, including certain strains of mice. However, in other mice strains, calorie restriction dramatically shortens the lifespan.
This detrimental effect in mice demonstrates a primary concern for testing anti-aging treatments in humans: A drug or lifestyle switch might shorten a healthy participant’s life. While it will take many years to find out if a treatment can truly increase longevity, we already know that wisdom only comes with time—and age.
If you regularly read this blog, you may know that the research questions that physiologists ask relate to wide range of topics—cells, tissues and organs, insects and animals, and how the environment influences all of these things. Nowhere is this more apparent than at the annual Experimental Biology meeting. This year, thousands of physiology-based research abstracts were presented over five days. Read on to learn about two research studies on extreme sports that caught our eye.
Credit: Ram Barkai
Ice swimming is growing in popularity, with hundreds of athletes worldwide giving this chilly sport a try. Human performance in water this cold—swims must take place in water that’s 5 degrees Celsius or colder—has not been well-studied. In a study presented at the EB meeting, researchers looked at how age, gender and environmental factors such as wind chill affected athletes during one-mile ice swims. Among other results, they found that age doesn’t have a large effect on swim times, suggesting that athletes can be competitive in the sport well into their 30s and 40s. This is significantly older than the average age of the athletes on the most recent U.S. Winter Olympic team (26 years old), giving hope to older athletes as the sport is being considered as a new Winter Olympics event.
Fifty kilometer (~31 mile) mountain ultramarathons test athletes aerobic and anaerobic fitness through changes in elevation, terrain and weather. Aerobic fitness refers to how the body uses energy when there is enough oxygen, such as the energy burn that occurs when running at a comfortable pace. Anaerobic fitness refers to the body’s ability to exercise when there’s not enough oxygen, such as during a sprint to the finish line at the end of a race. While it may seem that aerobic fitness would be a better predictor of how fast a person would finish an ultramarathon, researchers found that competitors with the best anaerobic fitness finished faster. That’s why exercises that build anaerobic endurance, such as uphill sprints, would be a worthwhile addition to the training regimen of anyone preparing for this type of race.
These studies were just the tip of the iceberg. Read more physiology research highlights from the EB meeting:
How exercise to protect the blood vessels from stress
Why a high-salt and high-sugar diet is a fast track to high blood pressure
The benefits of gastric bypass surgery that occur before the weight comes off
Elephant seals that protect themselves with CO2
What tobacco hornworms can tell us about fat metabolism
How an inhaler could protect against life-threatening accumulation of fluid in the lungs
Have you ever had a morning where you just did not have the energy to go out for your five-mile run? What if you woke up in New York City and had to run to Miami? That is the distance Alaskan Huskies run every year at the annual Iditarod sled dog race. How these amazing canine athletes accomplish this feat is interesting to scientists because it provides insight into how human performance can be maintained in challenging conditions.
Muscles get energy to exercise from glucose (sugar) and fats stored in the body. Muscles use oxygen from the air to transform the two into energy. Scientists originally assumed that the Alaskan Huskies used fat to sustain long periods of exercise. Huskies are fed a diet rich in fat, and the body stores fat in greater quantities than glucose. However, a recent study found that the dogs actually used glucose to sustain exercise and that the glucose was made from a part of fat called glycerol. The dogs took advantage of their fat stores, but they used the fat stores to make glucose.
Why go through the trouble of turning a part of fat into glucose rather than using fat as is? That answer is not entirely clear yet, but one possibility is that the dogs typically run the Iditarod at an average of 10 miles per hour, or six-minute miles, while pulling a sled. Muscles prefer glucose to fuel intense exercise because they can get more energy out of it for every molecule of oxygen breathed in. Sustaining such high speeds while pulling a load may require the use of glucose over fat. This is not to say that fat is not important for the dogs. As mentioned, the dogs use the fat, just not directly, and fat is good fuel during rest periods and recovery between running.
The Alaskan Huskies were bred to perform these amazing endurance feats, but we don’t know yet if human muscles can invoke the same rate of fat-to-glucose conversion processes to fuel exercise of such long distance. However, humans performing at such high speeds for prolonged periods would most likely need to do this same type of conversion.
Next time you’re not up for your morning run, channel your inner sled dog: Five miles really isn’t that bad.
Benjamin Miller, PhD, is an associate professor in the Department of Health and Exercise Science at Colorado State University. He co-directs the Translational Research in Aging and Chronic Disease (TRACD) Laboratory with Karyn Hamilton, PhD.
Dr. Miller with study participant.
Credit: Getty Images
The NFL has been under a lot of heat over concussion injuries in its players and the long-term brain injury and health impacts. With the size of the player and the speed he runs, it’s not hard to imagine the sheer force and damage that can occur from even a single collision. Woodpeckers, though, bang their head about 12,000 times a day at 10 times the impact of the average football hit. Why don’t woodpeckers get concussions?
The human brain floats in the skull in what is known as cerebrospinal fluid. This fluid acts as a cushion between the brain and the skull and helps lessen the impact of a blow to the head. Sudden, violent motions, such has from helmet-to-helmet contact, twist the brain or slam it against the skull. The movement stretches and damages the brain cells, causing problems in how the brain processes information.
Woodpeckers avoid brain injury because of the way their heads are designed. The bird’s brain fits snugly in the skull, so the brain doesn’t slosh around after a head impact. The brain is also oriented differently. Brains are shaped like a walnut: an oval-shaped dome. In humans, the dome faces the top of the head. In woodpeckers, the dome faces forward so the force of an impact is spread over a larger area. Size helps, too. Similar to how a cellphone stays intact after falling off the table while a laptop may not, a smaller brain has a better chance of getting away unharmed after a head injury.
The NFL recently found that more concussions were diagnosed in the 2015 season than in 2014. Officials and team physicians are not sure if the increase is due to more self-reporting by players and active identification of injury by trainers. Let’s root for Super Bowl 50 this Sunday to be full of drama on the field and 100 percent concussion free.
If temperatures in the teens (or the 50s for the warmer climates) make you grumble, be glad you’re not a mammal living in the Arctic or around Antarctica. These animals face much colder air temperatures of -40 to -76 degrees Fahrenheit. While humans bundle up with thick sweaters and jackets to get through the winter cold, mammals such as seals, penguins and polar bears stay warm with blubber, feathers and fur. How do these materials keep the arctic chill out?
Credit: Getty Images
The ability of a material to insulate depends on how easily it lets heat pass through—a property called thermal conductivity. Fat has a low conductivity, which means it slows heat getting out and helps keep heat in. Marine mammals such as whales and seals have a layer of blubber beneath their skin. The blubber insulates their body so they don’t lose body heat while swimming in icy waters.
Feather and fur also have low thermal conductivity and are good for keeping warm. They also trap air—another substance with low thermal conductivity—creating an insulating layer of air around the body. If the animal feels cold, goose bumps fluff up their feathers or fur, which traps more air to slow down heat loss. This is why down jackets are so cozy: Down traps air, and this air layer insulates us.
You can test these materials out for yourself: This experiment in Advances in Physiological Education uses bubble wrap and vegetable shortening to demonstrate how fat and air work as insulators. Show us how your experiment turned out. Tweet a photo and use the hashtag #ISpyPhysiology.
Credit: Stephen Secor
Thanksgiving dinner can leave the stomach feeling and looking stuffed beyond capacity. The Burmese python goes beyond the post-meal bulge: Its intestines and other organs grow too, and these changes happen within days of eating. A recent study in Physiological Genomics examined how the organs can grow so much so soon.
The Burmese python takes about 10 days to digest its meal. Within two days of eating, its metabolism and digestive processes are working 10 to 44 times faster. Three days after eating, its heart, liver, small intestines and other organs have grown to up to double in size. The meal is digested by the 10th day after eating, and these bodily changes have reversed. The Burmese python shrinks and returns back to its pre-meal state to go through this cycle again the next time it eats.
A multi-institutional team of researchers led by Todd Castoe, PhD, of the University of Texas at Arlington tracked how gene expression changed as the Burmese python’s body transformed. A gene is expressed when the protein it codes for is made. Greater expression of a gene means more of its protein is produced and present in the body. The researchers found that the expression of at least 2,000 genes changed after the snake ate. To their surprise, most of the shifts occurred soon after eating—within six hours. Genes that varied included those involved with organ structure and nutrient absorption. Gene expression matched and often preceded physiological changes and, like the bodily changes, returned to pre-eating state by the 10th day after eating.
According to the researchers, this study is the first to link the extreme and rapid eating-induced transformations of the Burmese python’s body directly to changes in gene expression and also the first to show how quickly gene expression changed.
So much of what we hear in health news today involves how what we eat or how much we move affects the way we live. For example, if we overeat sugar or unhealthy foods and don’t get enough exercise, we can find ourselves at increased risk for diabetes and cardiovascular disease. These can affect our quality of life or even shorten our lifespan.
As a comparative physiologist, I compare examples of animals and humans, how their diets affect their health and the factors that drive the development of cardiovascular disease with poor nutrition and diabetes.
I find birds to be the most interesting natural animal model of living successfully with high blood sugar. These amazing animals have blood sugar levels that are 1.5–2 times higher than the amount measured in mammals of similar body size, yet they display none of the typical characteristics that we associate with diabetes. This is because living with high blood sugar is just a normal part of their physiology. Another surprising fact: Unlike endurance athletes, who rely on sugar stores to power exercise, birds use fat to power flight. This is contrary to what people often assume.
Birds also defy the “rate of living theory of aging.” This theory suggests that animals with higher metabolisms (such as mice) do not live as long as those with low metabolisms (such as sloths). But birds go against this theory because they have very high metabolisms and are known to live relatively long lives.
We’ve still got a lot to learn about human health and disease from our fine, feathered friends and many other animals, too! To learn more about comparative physiology, check out the APS Dr. Dolittle blog.
Karen Sweazea, PhD, is an associate professor in the School of Nutrition & Health Promotion and the School of Life Sciences at Arizona State University.
New study describes how the brain controls movement in walking stick insects. Credit: Trista Rada/Flickr
What happens when you accidentally step into a hole? You were expecting a solid landing, but all of a sudden, it’s not there. One leg is left hanging, and you are caught off-guard. How the body reacts in this situation says a lot about how the brain controls the muscles used to walk. A new study in the Journal of Neurophysiology from researchers at the University of Cologne in Germany used this idea on walking stick insects to understand how the brain times the activation of the leg muscles to contract when walking.
The brain controls and receives information about the body through an intricate network of cells called the nervous system. Walking reflects how the brain coordinates the muscles, and understanding this interaction can provide insight into how the nervous system works. The researchers study walking in insects because their nervous systems have fewer cells and are less complicated.
Taking a step can be divided into two phases: swing, when the foot is in the air, and stance, when it’s on the ground. Each phase requires the activation of different sets of muscles in the legs. When the foot touches the ground is the transitioning point between the two phases. The researchers wanted to know how the brain knows to activate the leg muscles used in stance. Does it wait for the leg to feel the pressure of the foot hitting the ground? Or does it do it automatically because it dictates the walking pace?
To answer this question, the researchers developed a new apparatus that instantaneously generates a hole beneath the insect’s foot as the insect moves across it. The researchers looked at five leg muscles used in stance and found that only the activation of one muscle, the flexor tibiae, a muscle in the thigh-equivalent in an insect, depended on the foot making contact with the ground. The other four muscles activated whether or not the foot touched the ground. However, the intensity of the activation of all five muscles, which corresponds to the strength of the muscle’s contraction, depended on how hard the foot hit the surface.
So next time you’re walking on uneven ground, know that you’ll be thinking twice.
– Maggie Kuo
Reviewed by Matthias Gruhn, PhD