The competitive-eating elite will descend on New York City’s Coney Island this Fourth of July to flex their hot dog eating skills at the annual Nathan’s Famous Hot Dog Eating Contest. Last year, the male winner ate 62 hot dogs and the female winner ate 38 hot dogs in 10 minutes. Competitive eaters are surprisingly slight for the enormous amount of food they are able to consume. Where do all those hot dogs go?
The stomach is not a passive sack but an active organ that expands and contracts. An empty stomach holds about 1/4 cup, but when a meal is swallowed, the stomach expands to hold as much as 6 cups without stretching its walls. Besides relaxing to hold the meal, the stomach’s walls squeeze in and out and back and forth to move the food into the intestines, a process called gastric emptying. Researchers at the University of Pennsylvania wondered if speed eaters’ ability to keep down so many hot dogs was because their stomachs emptied faster or if their stomachs were trained to hold much more food than the average person.
The researchers recruited a professional speed eater and compared his gastric physiology to an individual with a big appetite. A gastric emptying test revealed that the professional speed eater’s stomach emptied slower than the regular eater. After 10 minutes, the regular eater consumed seven hot dogs, and his stomach was not stretched out. In contrast, the speed eater ate 36 hot dogs, and his stomach became a “massively distended, food-filled sac occupying most of the upper abdomen,” the researchers wrote. While the regular eater felt sick, the speed eater said he didn’t feel full, leading the researchers to wonder if the competitive-eating training made the stomach so stretchy and limp that the competitors never get the “full” physiological signal.
Although the study examined only one professional speed eater, the results support the idea that competitive speed eaters could eat large amounts of food in short periods of time not because their stomachs emptied faster but because their stomachs were able to enlarge dramatically.
The record for most hot dogs eaten is 69. How does the stomach look after that many? Not great, this video from ESPN shows.
The Aosta Valley in Italy where the Tor des Geants is held. Credit: iStock
Of all the extreme endurance races out there—such as the Ironman triathlon or 50- or 100-mile marathons—the Tor des Géants ultra-mountain marathon may be the most extreme. The course is 205 miles long on the rugged terrain of the Italian Alps with a cumulative elevation gain of 24,000 feet. Participants have 150 hours, little more than six days, to complete the course. These feats of ultra-endurance are fascinating for scientists because they showcase how the heart adapts when pushed to the limit. Previous studies have found that after 3- to 15-hour races like marathons and the Ironman triathlon, the heart doesn’t pump as well, a condition referred to as exercise-induced cardiac fatigue. A group of French researchers looked at what happened to the heart after running for over 100 hours in the Tor des Géants. They were surprised to find that unlike with marathons and triathlons, heart function improved after the ultra-mountain marathon race.
During a heartbeat, the heart fills with blood and then squeezes together to push out the blood. In situations in which the body constantly needs more oxygen, such as with exercise, the amount of blood filling the heart is one signal that tells the heart to keep beating harder. The more the heart fills, the stronger the heart contracts.
This study found that the runners’ hearts filled more during each heartbeat. The researchers think it’s because the amount of plasma, which is the liquid portion of blood, increased, raising the overall amount of blood in the body. But why it increased is not clear. Fluid intake could be one factor, says Michael Joyner, MD, an exercise physiologist not involved in the study, in a podcast. Runners in ultra-long races pay extra attention to staying hydrated and often maintain or gain weight from the extra fluids, he says. Stéphane Nottin, PhD, the lead investigator of the study, wonders if inflammation from the extreme physical stress or greater retention of sodium (the kidneys use sodium to absorb water) is also involved.
“Physiology has a long history of expedition-led investigations—whether it’s high altitude, desert—and this paper follows in that wonderful tradition,” Joyner says. Other current ongoing studies in this spirit include a Mount Everest climb to examine cognitive decline at low oxygen levels and a study on the heart of a swimmer swimming across the Pacific.
Sports and alcohol are a famous pair. Whether you’re a fan or an athlete, it’s common to follow up a great game with a drink or two. But does that drink affect your recovery after your workout? Researchers at California Polytechnic State University think that it might.
Rafael Jimenez, Amy Engel and a team of scientists studied this question by exercising rats for 60–90 minutes, then giving some of them ethanol, which is the type of alcohol found in alcoholic beverages. It was a heavy dose of alcohol, Jimenez says, noting that in other studies the dose produced a blood alcohol content of about 0.27 percent. (That’s equivalent to a 140-lb. man having about 9–10 drinks.) Three hours after the rats’ intoxication, the researchers measured the expression of recovery proteins in the rats’ muscles.
In particular, they measured the expression of PGC-1α, an important gene involved with the cell’s recovery response to exercise. PGC-1α is a major player in the creation of new mitochondria—the “engines” that provide cells with energy.
The expression of PGC-1α in muscle cells increased in all the rats after exercise. However, this increase was blunted in the rats that received ethanol. These findings are preliminary, but they suggest that drinking after exercise impairs recovery by keeping the cells from making more mitochondria. So next time you have a great workout, celebrate with a virgin margarita instead of an alcoholic drink to optimize recovery.
–Emily Johnson, PhD
Study authors Rafael Jimenez and Amy Engel present their poster “Effect of post-exercise ethanol on signaling pathways regulating mitochondrial biogenesis” at the Experimental Biology 2016 meeting in San Diego. Credit: Emily Johnson
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
Credit: Barnyz / Flikr
Spring is coming, and if you like to welcome the crisp March weather with water sports such as fishing and kayaking, remember that lakes, streams and oceans can have freezing temperatures this time of year. Falling into icy water is never part of the plan, but it happens even to the best cold-water adventurers. Exposure to cold water is dangerous and sometimes fatal but not because of hypothermia—low body temperature—as you might expect. In fact, hypothermia takes about half an hour to occur. Most cold-water drownings happen for another reason.
Being in cold water activates two opposing physiological responses at the same time. One is called the cold shock response, which activates the fight-or-flight response, a series of hormonal changes that rev up your body in stressful situations. This cold shock response causes you to gasp and breathe faster, increase your heart rate and pump blood to your muscles so you can escape the icy water quickly.
But mammals (including humans) also experience an opposite response to being in water called the diving reflex. It starts when cold water touches the face, and it prepares the body for a long dive. This response slows your heart rate, helps your body save oxygen and sends blood away from your muscles to your heart and brain.
These contradictory signals cause extreme stress on the heart. While the cold shock response dramatically increases blood pressure and heart rate, the diving reflex sends signals to reduce blood pressure and slow heart rate. These confusing signals can lead to irregular heartbeats (arrhythmias) and drastic changes in blood pressure, which can cause heart attack and lead to drowning. This is especially a risk for people with preexisting heart disease.
Bottom line: Be careful around bodies of cold water, and if you have a heart condition, don’t swim in them. It’s also wise to always swim with a buddy and have someone nearby who knows CPR whenever you are in the water. Following these tips can help you enjoy the weather, not the emergency room, during this spring season.
Learn more about the physiology of drowning.
Emily Johnson, PhD, ACSM clinical exercise physiologist, is a postdoctoral fellow at Washington State University Spokane.
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
I live in South Dakota where the winter days can be frigid and very dry. Many people, including me, have difficulty breathing while exercising in the winter because our airways temporarily narrow during exercise. This condition is called exercise-induced bronchoconstriction (EIB), formerly known as exercise-induced asthma, and it’s often triggered by working out in cold, dry air.
Scientists believe it’s the dryness of the air breathed in and the quality of the air, not the coldness, that cause the airways to narrow. The lungs have a number of defense mechanisms and reflexes to protect the small airspaces from dry air and particles in the air. The extensive network of airways moistens and warms inhaled air so that by the time the air arrives at the gas-exchange areas—where oxygen enters the blood and carbon dioxide leaves—it is humidified and the same temperature as the body. The airways are lined with mucus that helps catch inhaled particles through its stickiness. The airways also can constrict to prevent particles and dry air from getting farther into the lungs. Narrowing causes problems, however, because less air reaches the gas-exchange areas, preventing the body from getting enough oxygen.
How can you tell if you have EIB? You will experience one or more of the following symptoms, which last 10 to 15 minutes after you’ve finished exercising:
- shortness of breath or wheezing,
- decreased endurance,
- tightness in the chest,
- upset stomach and
- sore throat
While 90 percent of people with asthma have EIB, not everyone with EIB has asthma. You’ll need to see an allergist to determine whether your symptoms are solely exercise-induced, are a reaction to irritants in the air or are indications you have asthma.
EIB doesn’t have to keep you from exercising in the winter. In fact, many elite cross-country skiers, world-class figure skaters and ice hockey players have EIB. Here are some suggestions from the American College of Allergy, Asthma and Immunology to relieve your symptoms:
- Warm up with gentle exercises for 15 minutes before starting intense exercise.
- Cover your mouth and nose with a scarf or face mask.
- Try to breathe through your nose.
Medicine that widens the airways can also be prescribed to help prevent your symptoms and attacks. I try not to take a deep breath when I go outside on a cold South Dakota winter day. Then, I head out on a four-mile walk with my golden retriever.
Barb Goodman, PhD, is a a professor of physiology at the University of South Dakota.
Credit: Greg McFall/Flikr
The appeal of freediving may lie in its freedom. Freedivers, without cumbersome scuba gear and noisy regulators, easily glide through tranquil waters toward coral or rocky reefs with scenes unobstructed by bubble trails. With dives often exceeding five minutes, they get to see up close and personal the colorful marine life that typically flees from noisy scuba divers. Freedivers can extend their time underwater by hyperventilating—breathing in and out rapidly—before diving. This allows more oxygen into the lungs, but if the dive is not planned and executed well, it can also have dangerous results.
Oxygen is key to our survival: It’s used to make ATP, a molecule that fuels everything we do. When we breathe in, oxygen in the air travels into our lungs, goes into our blood and finally makes it to our cells, where ATP is produced. Carbon dioxide (CO2) is also made during ATP production. As we make more and more ATP, CO2 builds up. To get rid of this accumulated CO2, CO2 flows from the cells to the blood and then into the lungs, where we eventually exhale it.
The presence of CO2 in our lungs means there is less room for oxygen. Hyperventilating can cut the amount of CO2 in half, allowing more space for oxygen. With this additional oxygen, freedivers can stay underwater a little longer, but they can misjudge when they need to head to the surface for air.
Low oxygen level is not what prompts us to breathe. Rather it’s the accumulation of CO2. Under normal breathing, the buildup of CO2 signals us to breathe before oxygen becomes too low. However, hyperventilating reduces CO2, and the signal to breathe comes later. Without a timely signal, a freediver may dive too long and allow too much oxygen to be consumed. As the diver finally heads to the surface, oxygen can become too low for the brain to maintain consciousness. The consequences can be fatal.
Cassondra Williams, PhD, is a postdoctoral fellow at Scripps Institution of Oceanography.
Credit: Getty Images
Those who are active year-round know that summer workouts are more tiring than those done in cooler weather. The good news is that it’s not a sign that you’re suddenly out of shape. Exercising in warm temperatures is not the same as exercising in cooler temperatures and the body’s physiology has to adjust. How does the body adapt and can these changes translate to performance gains in cooler temperatures?
The body takes about 10 days to acclimate to exercising in heat. The most noticeable signs that it has adapted to warmer weather are sweating more easily and a lower exercising heart rate. Less perceptible physiological changes include greater volume of plasma—the liquid portion of the blood in which the red blood cells are suspended—less salt released through sweat and more efficient heart and muscle function.
Because these physiological adaptations improve exercise performance in heat, scientists and athletes have wondered if these changes also mean enhanced performance in cool conditions. The jury, though, is still out. A study in 2010 in the Journal of Applied Physiology reported that exercising in heat did improve exercise performance in cooler weather. A new study published last month in the American Journal of Physiology—Heart and Circulatory Physiology concluded the opposite: heat training only improved performance in hot conditions, but not temperate ones. Nonetheless, both studies show that the body can adapt to new conditions relatively quickly. So, when you find it hard to catch up when it’s hot, be patient. You’re not out of shape, it’s just your body is catching up.
The muscles in our body contract and relax to walk and move us through our day. Even when we are not in motion, our muscles are actively working to keep us upright and steady. Surprisingly, this constant action doesn’t fatigue us like running at top speed for 30 seconds does. What is the physiological basis for why some activities exhaust us while others we don’t even register?
Muscles are made up of three types of fibers identified by how quickly they contract: slow, fast or super-fast. Besides contraction speed differences, the fibers fuel themselves differently—either through oxygen, glucose (sugar) or both. They also range in size, amount of power they produce and how quickly they get tired. Every muscle group in the body contains all three types but the proportions of each reflect the muscle’s purpose.
- Slow-contracting fibers derive their energy mainly from oxygen. They are resistant to fatigue and can contract for long periods of time. Muscles in the back contain a large number of slow fibers, which help sustain an upright posture for extended periods.
- Super-fast fibers get their energy mostly from glucose stores in the body. These fibers are larger in diameter than slow fibers and, because of their size, can generate more powerful contractions. However, super-fast fibers exhaust quickly. Muscles in the arms have more of these fibers, enabling them to produce large amounts of tension quickly, as when lifting objects.
- Fast-contracting fibers use both oxygen and glucose for energy. The size and fatigue rate of these fibers are in between the other two.
Just as fiber makeup varies between muscle groups, it also varies between individuals and can reflect the sports a person is best suited for. Marathon runners, who run for extended periods of time, have a large number of slow fibers in their quadriceps. Sprinters, on the other hand, need quick bursts of power and have a large number of fast oxygen/glucose-using fibers in theirs.
Former world champion sprinter Colin Jackson. Credit: Guy Evans/Flickr
A recent study in Journal of Applied Physiology looked at the fiber makeup of the quadricep of former world champion sprinter Colin Jackson. The investigators found that Jackson has a high number of the super-fast glucose-using fibers, which was surprising to them because other elite sprinters studied have very few. The researchers noted that animals that sprint, such as cheetahs and horses, also have a high percentage of these super-fast fibers and suggested that sprinting ability could be partly related to the number of these fibers. Jackson’s unique muscle profile “provides a scientific basis for the high level of sprinting success he achieved during his career,” the researchers stated.
– Maggie Kuo
Reviewed by Scott Trappe, PhD