This week, the I Spy Physiology blog answers a reader question: Why do we get dizzy when getting out of a hot tub?
There may not be a better way to chase away the winter “blahs” than soaking in the hot tub or standing under a steaming shower. However, sometimes, after a lengthy soak or steam you may feel lightheaded when you stand up. You may start to feel woozy and your balance may waver. You may even see stars for a moment or faint. Why does this happen?
When body temperature rises due to hot water, hot weather or fever, the body activates mechanisms to cool down toward normal temperature (97–99°F). The blood coursing through the body must rise to the surface of the skin, releasing heat, to reduce core temperature. This happens through a process called vasodilation. During vasodilation, blood vessels carrying blood away from the heart (arteries) open up to allow a larger volume of blood to flow through them. Blood flowing through the arteries near the skin’s surface releases heat into the environment and cools the body. However, when many arteries open up at the same time (while a person is standing up), gravity pulls the blood into the legs and away from the brain and heart. Pooling of blood in the legs can cause dizziness or lightheadedness because the brain and heart aren’t getting enough blood.
Lightheadedness and even fainting are the body’s way of “fixing” the lack of blood in the brain and heart. Once the brain, heart and legs are at the same level (when a person is lying down), blood flows into each organ more easily because gravity no longer pulls so much blood into the legs. Flexing the muscles is another way to return more blood to the brain and heart. Muscle contraction works against gravity and forces blood back to the heart and ultimately the brain. This provides the brain with enough blood volume to eliminate wooziness.
The next time you are enjoying a dip in a hot tub or a steaming shower, pause, flex your muscles and steady yourself before stepping out.
Jessica C. Taylor, PhD, is the Senior Manager of Higher Education Programs at the American Physiological Society. She is a cardiovascular physiologist, exercise enthusiast and firm believer in warming up in hot water.
When young people think about their muscles, they often focus on enhancing their muscle size and strength for cosmetic or athletic reasons. Those older than 50, however, need to be more concerned with just keeping the muscle they have. On average, people over the age of 50 lose 1 to 2 percent of their muscle mass each year, and after age 60, this number increases to 3 percent. Bed rest, lack of exercise and sedentary behavior in the elderly can speed up this gradual loss over time. Why is maintaining muscle so important for the elderly?
The simplest reason is that muscle is essential for all kinds of movement. Mobility is a crucial component of maintaining independence as we age. Adequate muscle mass and strength allow seniors to continue performing simple daily activities—things like bathing, getting dressed and preparing food—without assistance. Another less obvious reason is that muscle burns a large percentage of the energy that we get from the foods we eat. Losing muscle mass means that we do not use the energy from food as effectively, which can lead to chronic health conditions. In fact, loss of muscle mass is a major contributor to the increased rates of type 2 diabetes in older adults.
Current research has revealed, however, that muscle size is not the only, or even best measure of muscle health. Scientists have traditionally used the term “sarcopenia” to refer to aged-related loss of muscle mass, but many scientists are now focusing more on “dynapenia,” which indicates the loss of muscle function due to aging. New research is showing that how well muscle works can be just as important as how much muscle mass remains. In fact, a person with a smaller amount of muscle mass whose muscle function is good may be stronger and healthier than someone with more muscle mass but poor muscle function. This realization has led to new strategies for promoting muscle health in aging. Although maintaining muscle mass is still important, new approaches are targeting improvement in muscle function. These strategies go beyond simply lifting weights and look at ways to make the inner machinery of the muscle work better. Although nothing can completely stop the loss of muscle function with age, promising new nutritional and exercise therapies are emerging to substantially slow the decline, helping seniors stay active and independent for as long as possible.
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.
If getting more exercise is one of your New Year’s resolutions, here is another reason to stick with it: daily exercise—which is known to lower blood pressure—has also been shown to reduce stress and anxiety. I am not the first to notice that physical activity improves my ability to respond to stressful situations, but as a physiologist, I naturally wonder about the biological basis of this observation.
The hippocampus—one of the brain regions that regulates anxiety levels—becomes activated during both exercise and stress. Research suggests that exercise can calm some of the nerve cells in the hippocampus that become overstimulated during times of stress. While we don’t fully understand the mechanisms, we do know that certain chemical signals in the brain inhibit nerve cell activity, and some of these signals are likely responsible for the observed reduction in stress and anxiety.
Reduced anxiety and stress immediately after physical activity is not the only benefit of exercise. Blood pressure also declines to healthier levels within minutes after exercising. Studies suggest that exercise causes vasodilation, or widening of the blood vessels. When blood vessels open wider, it allows the blood to flow more easily, thereby lowering the pressure of the blood inside the vessels. Activation of histamine receptors is one mechanism that contributes to the reduction in blood pressure following exercise.
While there are many other benefits to regular exercise, the reductions in stress and blood pressure occur immediately and last for many hours. So, consider engaging in a physically active lifestyle that includes daily exercise, and encourage family and friends to join in. The result could be less stress, less anxiety, and lower blood pressure. What better way to start 2018?
William B. Farquhar, PhD, is a professor in the department of kinesiology and applied physiology at the University of Delaware. In addition to being a member of the American Physiological Society, he is a Fellow of the American College of Sports Medicine.
Your gut contains tens of trillions of microorganisms, including at least 1,000 different species of known bacteria. Even though these bacteria are microscopic in size, they are so abundant that they make up 1 to 3 percent of your total body mass! Many of these microorganisms that live in the body are actually beneficial to your health, although some can be harmful. The “good” bacteria in your digestive system protect your body by preventing the growth of “bad” bacteria that can make you sick. They also serve an essential function in food digestion by breaking down foods and proteins and synthesizing vitamins and nutrients. Recently, researchers have shown that gut bacteria, or microbiota, may play a role in diseases such as diabetes, obesity and Alzheimer’s disease, and they can affect distant organs such as the brain and even bone.
One of the ways that the gut affects bone is by regulating mineral absorption. As food passes through the body, the gastrointestinal (GI) system controls the amount of minerals that are absorbed from the food into the bloodstream. Many of these minerals—including calcium, phosphorous, and magnesium—are essential for healthy bones. In fact, studies report that people with GI diseases such as inflammatory bowel disease can experience bone complications.
Other research has added support to the theory that gut bacteria may affect the bone by contributing to the absorption of nutrients. Mouse studies have shown that the presence or absence of gut microbiota can actually change the structure and density of bone. Bone density, or bone mass, is one indicator of how strong and healthy your bones are. It’s not exactly clear how or why gut bacteria affect bone, but researchers believe that one way is by regulating how much calcium is absorbed into the body.
Taking probiotics is known to help maintain a healthy gut microbiota. Probiotics are live bacteria that can be taken by mouth as a dietary supplement. They contribute to the health of the digestive system by promoting the growth of good bacteria and inhibiting harmful bacteria. But new research is showing that they can also have beneficial effects on the bone.
While scientists continue to explore the link between the gut bacteria and bone, a few lifestyle adjustments can help protect your bones:
- Include plenty of calcium and vitamin D in your diet.
- Exercise regularly (preferably with weight-bearing exercises that strengthen your bones).
- Quit smoking and limit alcohol consumption.
- Avoid using steroid drugs, which can weaken your bones.
- Get bone mineral density testing according to the schedule recommended by your doctor.
Naiomy Rios-Arce, BS, is a PhD candidate in the Comparative Medicine and Integrative Biology program in the Department of Physiology at Michigan State University. Her research focuses on understanding the mechanism by which probiotics can affect bone density. Naiomy is originally from Hatillo, Puerto Rico.
With the new year upon us, many people are setting new goals for themselves related to improving their health or focusing on career-related goals. If establishing better exercise and nutrition habits are part of your quest to attain optimal health and productivity in 2018, you are not alone. New gym memberships are likely to rise in the coming months, and some may try nutritional products such as fruit and vegetable juice concoctions touted to enhance performance and overall health. The global juicing industry has gained a lot of traction in the last several years due to a wider health awareness among consumers. Emerging evidence suggests that casting beets in the starring role of your juice habit—along with aerobic exercise—may be one potential route to improving your cardiovascular health, and more recently shown, brain health.
Beets are a good source of antioxidants, minerals and nitrates. The nitrate-rich properties of beets have caught the attention of researchers, particularly those in the field of vascular medicine. Nitrates in food are converted to nitric oxide in the body. Nitric oxide relaxes the walls of the arteries, lowering blood pressure and increasing blood flow to muscles. That is one of the reasons why the nitrates in beetroot juice have been shown to enhance exercise performance in high-performing athletes, as well as in less elite exercisers.
In addition to the cardiovascular and performance benefits of consuming beets, recent studies suggest that the root vegetable may also be linked to brain health. One study found that older adults who performed aerobic exercise for six weeks and drank beetroot juice daily had greater improvements in brain activity related to movement than the participants who exercised without drinking beetroot juice. The brain networks of the juicing group more closely resembled the brains of younger adults, suggesting that when combined with exercise, beets can enhance the brain’s ability to make new connections between brain cells. Another study showed that young adults who drank a single dose of beetroot juice had increased blood flow to the area of the brain involved in higher-order thinking. The study participants also fared better in cognitive tasks such as basic math.
So, before you lace up your running shoes or settle back into your office chair, consider topping off with a dose of beetroot to keep the juices flowing.
Yasina Somani, MS, is a PhD student in the Cardiovascular Aging and Exercise Lab at Penn State. She is interested in studying the effects of novel exercise and nutritional therapies on cardiovascular outcomes in both healthy and clinical populations.
Every January gym memberships spike and the wait to get on the treadmill gets longer. This happens because about 40 percent of Americans make New Year’s resolutions, the most common of which are exercising more and improving fitness. Some people may believe in the concept of “no pain no gain,” but it’s a common misconception that if your muscles don’t feel sore then you are not working out hard enough. Many athletes reach for nonsteroidal anti-inflammatory drugs (NSAIDs) to ease the aches and pains of a hard workout. Naproxen and ibuprofen are two commonly used NSAIDs that are available over the counter. Studies estimate that up to 75 percent of long-distance runners take NSAIDs before, after or during training.
Microscopic tears in the muscles cause soreness following strenuous exercise. In response to injury, the body produces compounds called prostaglandins, which play an important role in healing. NSAIDs reduce pain by slowing the production of prostaglandins, which reduces inflammation. The problem is that inflammation also plays an important role in healing damaged muscle as well as helping the muscle growth that occurs with regular exercise. In other words, taking NSAIDs after a workout may not necessarily be a good thing.
A recent study in mice found that levels of a specific prostaglandin increased after minor muscle injury. This particular prostaglandin stimulated regeneration of new muscle stem cells to repair the damage. But when the mice were given NSAIDs their bodies produced fewer active stem cells, leading to weaker muscles even after the injuries had healed.
Other negative effects, such as kidney injury, have been associated with NSAIDs. In one study, elite athletes took either 400 milligrams of ibuprofen or a placebo every four hours during a 50-mile race. At the end of the race, more than 40 percent of the runners tested high for creatinine, a marker of kidney injury. Runners who took ibuprofen instead of the placebo were more likely to develop kidney injury and their degree of injury tended to be worse. The study did not explain why ibuprofen may cause kidney injury in elite athletes, and it’s not clear whether the risks are similar in people participating in less-intense workouts. More studies are needed to examine the effects of ibuprofen following different types of exercise.
If exercising is one of your New Year’s resolutions, start off slow to avoid muscle pain. If you do overdo it, try easing your aches with a warm heating pad before reaching for the ibuprofen.
John Chatham, DPhil, is a professor of pathology and director of the Division of Molecular and Cellular Pathology at the University of Alabama at Birmingham.
Our blog is on winter break this week. See you in 2018! Have a safe and happy holiday season.
– Erica Roth
Another physiology-filled year on the I Spy Physiology blog is almost over. This year, we’ve explored dozens of topics, ranging from skin cancer, gut health and spinal cord injury to the mystery of how hibernating animals’ muscles remain strong. We’ve celebrated women in science and smiled at the thought of turkeys running on treadmills. Today, we’re highlighting the 10 most-read posts of 2017.
Scholarly articles highlight the need for more research about women’s responses to illness and disease risk. In that vein, our most popular post this year looked at the relationship between sex-specific hormones and asthma. Posts about the danger of e-cigs—especially in the under-21 set—and how muscle rebuilds during the daunting feat of cycling the 500-mile Colorado Trail rounded out the top three. Take a look at this year’s top 10:
- When Hormones Take Your Breath Away
- The Trouble with E-Cigs: Why They May Pose More Harm than Good
- Muscle Rebuilding on the Colorado Trail
- Beer Does a Body Good?
- Meet Karyn Hamilton, Health and Exercise Science Professor
- Dog Gazing: Bond between Hound and Human
- Why Does Air Pollution Affect More Women than Men?
- When Vampires Attack: How Your Body Reacts to Extreme Blood Loss
- Microvesicles and Blood Vessels and Exercise, Oh My!
- The Hispanic Paradox: Why Are Some Ethnic Groups Living Longer than Others?
We’d love to hear what you’d like us to feature next year. Share your thoughts in the comments or send us an email. And don’t forget to follow our blog in 2018.
– Erica Roth
If you tend to see the proverbial glass as half empty instead of half full, you may want to rethink your position. Looking on the bright side and expecting good things to happen may have a positive effect on your physical health. An optimistic outlook on life may reduce your cardiovascular disease risk, lower blood pressure and improve overall health and longevity. It can also reduce sensitivity to pain and may help people manage chronic pain more easily.
You may be skeptical or cautiously optimistic about this. How can simple optimism lead to good health? The answer is still not entirely clear, but scientists are slowly uncovering the biological details. They’ve learned that the body’s response to stress may be an important factor.
When the body is stressed, it sends biological messengers called stress hormones into the bloodstream to tell different organs to respond in various ways. One of the major stress hormones is cortisol. When cortisol is high, the body responds by making unhealthy amounts of certain substances (such as cholesterol) that can harm the heart. These substances may damage and cause inflammation in the blood vessels. Inflammation may also lead to more damage in the circulatory system. This unfavorable chain of events may increase the risk of heart disease.
People who look on the bright side may be more likely to have markers of good health—including lower stress hormone levels—even when they face stressful situations. One study found rats with pessimistic behavior traits had more inflammation than their optimistic counterparts. Lower cortisol and inflammation levels may be due to decreased activity of the fight-or-flight nervous response, although more research is needed.
Motivation may also play a role in boosting the health of optimists. People who think positively may be more motivated and tend to make more of an effort in social interactions than those who are pessimistic. This can lead to healthier social connections and an increase in beneficial behaviors such as exercising regularly and following a healthy diet. The motivational aspects of optimism (or pessimism) may also affect a person’s behavioral response to stress.
December 21 is “Look on the bright side” day. Try a visualization exercise to boost your optimism. It may have a positive effect on your overall health.
– Audrey Vasauskas
Shaina Willen, MD, of Vanderbilt University Medical Center, presents her poster at the Physiological and Pathophysiological Consequences of Sickle Cell Disease conference.
Sickle cell disease (SCD) is a lifelong disorder of the red blood cells. It’s caused by a mutation in a single gene and affects about 100,000 people in the U.S. Normal red blood cells are round, a shape that helps the cells carry oxygen around the body. But red blood cells in people with SCD can become abnormally shaped like a crescent (sickle), which can cause blood cells to get stuck in blood vessels and interfere with blood flow, leading to severe pain.
Scientists and medical doctors who specialize in SCD gathered last month in Washington, D.C., for the American Physiological Society conference “Physiological and Pathophysiological Consequences of Sickle Cell Disease.” They discussed new research into the causes of the disease and new therapies that can treat and even prevent SCD-related pain episodes. Read on to learn more about their findings.
Certain patients with SCD may have a higher risk than others of developing complications—such as increased pain, stroke, eye problems and kidney disease—but finding out which patients have a higher risk is challenging. New research from Vanderbilt University Medical Center has uncovered a genetic marker that may be able to identify which patients are more likely to have these complications.
Emotional stress is known to trigger or worsen physical symptoms of disease, including some types of pain. A group of researchers from California found that stress and the anticipation of pain causes blood vessels to become narrower (vasoconstriction). In people with SCD, vasoconstriction can be dangerous because abnormally shaped (sickled) cells may be more likely to get stuck in the blood vessels and block blood flow.
A healthy digestive system is typically filled with various types of bacteria that aid in digestion. However, researchers from Howard University found that people with SCD are more likely to have higher levels of one specific bacterium, Veillonella. Veillonella link together to form a film in the digestive tract, which can attract red blood cells. When red blood cells stick to the film, it can block blood flow to the rest of the body, which causes increased pain. This discovery may help scientists find a way to rebalance gut bacteria levels and reduce symptoms.
These studies are just a few examples of the high-caliber SCD research being done. Read more highlights from this year’s conference:
Alzheimer’s drugs may improve red blood cell function and quality of life
Scientists explore ways to create red blood cells outside the body and prevent sickling
– Erica Roth