Forget 98.6°F. Humans Are Cooling off — Here’s Why
By Kristen Fischer
The "normal" body temperature of 98.6°F (37°C) is actually not so normal. New research finds the average human body temperature of Americans has dropped.
"What everybody grew up learning, which is that our normal temperature is 98.6, is wrong," said Dr. Julie Parsonnet, a professor of medicine as well as health research and policy at Stanford University School of Medicine.
The 98.6°F standard was established by a German doctor in 1851. Recent studies have indicated that's too high; research on 35,000 British people found their average was 97.9°F.
Parsonnet's study published this week in eLife. It found that temperature changes since 1851 reflect a historical pattern instead of an error. They contend the decrease is the result of environmental changes over the past 200 years that have affected human physiology.
Parsonnet looked at data from 1862 through 1930, 1971 through 1975, and 2007 through 2017. It included 677,423 temperature measurements.
The body temperature of men born in the 2000s is 1.06°F degrees lower, on average, than men born in the early 1800s. Women have temps about 0.58°F lower than those born in the 1890s. That means body temperatures declined 0.05°F every decade.
Parsonnet's team also found a decline in temperature since the 1960s, not just since the Civil War.
Body temperature is complicated, Parsonnet says. It can vary not just from person to person but at different times of day and at different ages.
It can be almost half a degree higher in the afternoon than morning. It's much lower in older adults. Your weight and height as well as hot or humid weather can also affect it, Parsonnet says.
In her experience, Parsonnet says at least 75 percent of normal temperatures are below 98.6°F.
"Even in younger adults at the end of the day, when temperatures are at their highest, the temperature still doesn't get up to 98.6," she said. "In the elderly, it would be quite unusual to have a temperature as high as 98.6."
"The threshold for fever is generally held as 1°C above normal," said Dr. Bradley Uren, assistant professor of emergency medicine at Michigan Medicine. "A fever is generally held as 38°C, or 100.4°F."
"It is rare to see a patient at exactly 98.6," he noted. "A temperature is just one piece of information that physicians must and do consider in determining a course of treatment for an individual."
Even though our temperatures can fluctuate, doctors still know what's generally normal. They also know to look for variations in temperature, which can indicate a medical condition, Uren says.
"Physicians must take into account the entirety of a patient's condition in determining if a temperature, either higher or lower, or even within the normal range, is significant," Uren said.
"For example, patients may be treated for infection even with a normal temperature if the other historical and physical findings, and the patient's overall condition, is consistent with infection," he said.
Dr. Amy Mullins, medical director of quality improvement for the American Academy of Family Physicians, notes that the study won't change how patients or doctors should define fevers.
Why Temps Are Falling
It's possible that some of these changes may be because thermometers provide more accurate readings, Parsonnet noted in her study.
However, that doesn't explain all of it. Temperatures declined over time even when her team controlled for different devices.
Susan Yeargin, Ph.D., associate professor of exercise science at University of South Carolina, has tested all types of temperature devices in diagnosing hyper- and hypothermia. They were inaccurate compared to the rectal temperature.
"Each person's unique normothermic body temperature should be considered by healthcare providers. Certain medications can influence a person's regular 'set point' temperature, and obviously hot and cold outdoor temperatures can affect a person's body temperature over time," Yeargin said.
"When healthcare providers give advice to individuals about these medications and environments, their unique normothermic body temperature should be considered," she said.
According to Parsonnet, other reasons for the decline in body temperature over time could be that we're also using less energy and have a lower metabolic rate than in the past.
The reduction may be due to a population-wide decline in inflammation. Generally, inflammation increases our metabolism and raises temperature.
Because of improvements in public health, this could be why inflammation has decreased. The ambient temperatures we live in, thanks to heating and air conditioning, could be factors in lower metabolic rates.
"I think it's most likely because we have much less inflammation in our bodies now than we did when the standard was developed in the mid-19th century," Parsonnet said.
"We have less inflammation because we have far fewer chronic infectious diseases like tuberculosis and periodontal disease, far less recurrent infection, shifts in our microbiomes, and we also have learned how to combat inflammation directly through better diets, and also with things like nonsteroidal drugs and statins," she explained.
In general, humans are physiologically different than we were in the past, Parsonnet says.
Reposted with permission from Healthline.
- How modern life is transforming the human skeleton - BBC Future ›
- Designing bodies: How tech is changing what it means to be human ... ›
- How to Stay Cool Without Air Conditioning ›
- What Is the Normal Body Temperature: Babies, Kids, Adults, and More ›
- How to Tell If You Have a Fever: Symptoms, Next Steps, and More ›
EcoWatch Daily Newsletter
The U.S. Environmental Protection Agency (EPA) wrote a letter to the Army Corps of Engineers last week to say that it would not oppose or put a stop to a huge copper and gold mine near the world's largest sockeye salmon fishery, as The Washington Post reported.
- Trump Pushed for Mining Project That Could Destroy Alaska Salmon ... ›
- The Resource War Over Pebble Mine in Alaska's Bristol Bay ›
- 'The Wrong Mine in the Wrong Place': Former Republican EPA ... ›
The nationwide horror at the killing of George Floyd by the Minneapolis police has triggered protests in 75 cities. People are demonstrating against the systemic racism that has made people of color targets of lethal actions by law enforcement. In response, elected officials and public health experts are walking a fine line of affirming the rights of protestors while simultaneously worrying that the protests will lead to a new wave of coronavirus infections.
- Will Protests Spark a Second Viral Wave? - The New York Times ›
- Protests could cause catastrophic setback for controlling coronavirus ... ›
- Coronavirus lockdown protests risk your health and America's ... ›
- Some Protesters Call For Ending Coronavirus Lockdowns, Despite ... ›
- How Minneapolis Protesters Contend With COVID-19 | Time ›
By Sara Lindberg
Whether you've hit a workout plateau or you're just ready to turn things up a notch, adding more strenuous exercise — also known as high-intensity exercise — to your overall fitness routine is one way to increase your calorie burn, improve your heart health, and boost your metabolism.
However, to do it safely and effectively, there are some guidelines you should follow. Keep reading to learn more about the benefits of vigorous exercise and how to safely dial up the intensity of your workouts.
What Is Considered Strenuous Exercise?<p>When it comes to exercise, the intensity of how hard you work out is just as important as the duration of your exercise session. In general, exercise intensity is divided into three categories:</p><ul><li>low</li><li>moderate</li><li>vigorous or strenuous</li></ul><p>For an activity to be vigorous, you need to work at 70 to 85 percent of your maximum heart rate, according to the<a href="https://www.heart.org/en/healthy-living/fitness/fitness-basics/target-heart-rates" target="_blank"> American Heart Association</a>. Examples of vigorous exercise include:</p><ul><li>running</li><li>cycling at 10 mph or faster</li><li>walking briskly uphill with a heavy backpack</li><li>jumping rope</li></ul><p>Low to moderate exercise is easier to sustain for longer periods since you work below 70 percent of your maximum heart rate and, sometimes, well below that level.</p><p>To reap health benefits, the <a href="https://www.hhs.gov/fitness/be-active/physical-activity-guidelines-for-americans/index.html" target="_blank">Physical Activity Guidelines for Americans</a> recommends that people age 18 and older get one of the following:</p><ul><li><strong>150 minutes</strong> of moderate-intensity aerobic activity per week</li><li><strong>75 minutes</strong> of vigorous aerobic activity per week</li><li><strong>combination of both types</strong> of activity spread throughout the week</li></ul>
Strenuous Exercise Vs. Moderate Exercise<p>Increasing your exercise intensity is fairly simple to do. You can still participate in your favorite activities — just at a more vigorous pace.</p><p>One of the benefits of more strenuous exercise is that you can reap the same rewards as moderate-intensity exercise but in less time. So, if time is of the essence, doing a more strenuous 20-minute workout can be just as beneficial as doing a slower 40-minute workout session.</p><p>Here are some examples of <a href="https://www.cdc.gov/nccdphp/dnpa/physical/pdf/pa_intensity_table_2_1.pdf" target="_blank">strenuous vs. moderate exercise<span></span></a>.</p><table><tbody><tr><th>Moderate intensity</th><th>Strenuous intensity</th></tr><tr><td>bicycling at less than 10 mph</td><td>bicycling at more than 10 mph</td></tr><tr><td>walking briskly</td><td>running, or hiking uphill at a steady pace</td></tr><tr><td>jog-walk intervals</td><td>water jogging/running</td></tr><tr><td>shooting baskets in basketball</td><td>playing a basketball game</td></tr><tr><td>playing doubles tennis</td><td>playing singles tennis</td></tr><tr><td>raking leaves or mowing the lawn</td><td>shoveling more than 10 lbs. per minute, digging ditches</td></tr><tr><td>walking stairs</td><td>running stairs</td></tr></tbody></table>
Benefits of Vigorous Exercise<p>Besides being more efficient, turning up the heat on your fitness sessions can benefit your health in a variety of ways. Let's take a closer look at some of the evidence-based benefits of a higher intensity workout.</p><ul><li><strong>Higher calorie burn.</strong> According to the <a href="https://www.acefitness.org/education-and-resources/professional/expert-articles/5008/7-things-to-know-about-excess-post-exercise-oxygen-consumption-epoc/?utm_source=Rakuten&utm_medium=10&ranMID=42334&ranEAID=TnL5HPStwNw&ranSiteID=TnL5HPStwNw-hYlKnAcfzfixAUsvnO6Ubw" target="_blank">American Council on Exercise</a>, working out at a higher intensity requires more oxygen, which burns more calories. It also contributes to excess post-exercise oxygen consumption (EPOC) or the "afterburn effect" that allows you to continue burning calories even after you finish working out. This means your metabolism will stay elevated for longer after a vigorous exercise session.</li><li><strong>More weight loss.</strong> A <a href="https://www.healthline.com/health-news/interval-workouts-will-help-you-lose-weight-more-quickly" target="_blank">higher calorie burn</a> and an elevated metabolism will help you lose weight more quickly than doing low- or moderate-intensity exercise.</li><li><strong>Improved heart health.</strong> According to a <a href="https://www.ncbi.nlm.nih.gov/pubmed/16377300" target="_blank">2012 study</a>, high- and moderate-intensity exercise appears to offer low chance of cardiovascular events, even in those with heart disease. Cardiovascular benefits may include improvements in:<ul><li><a href="https://www.healthline.com/health/diastole-vs-systole" target="_blank">diastolic blood pressure</a></li><li><a href="https://www.healthline.com/nutrition/15-ways-to-lower-blood-sugar#TOC_TITLE_HDR_1" target="_blank">blood sugar control</a></li><li>aerobic capacity</li></ul></li><li><strong>Improved mood.</strong> High-intensity exercise may also boost your mood. According to a large <a href="https://www.jstage.jst.go.jp/article/jpts/27/4/27_jpts-2014-736/_article" target="_blank">2015 study</a> that analyzed the data of more than 12,000 participants, researchers found a significant link between strenuous exercise and fewer depressive symptoms.</li><li><strong>Lower risk of mortality.</strong> According to a 2015 <a href="https://www.ncbi.nlm.nih.gov/pubmed/25844882" target="_blank">study</a>, researchers found that vigorous activity may be key to avoiding an early death. The study, which followed 204,542 people for more than 6 years, reported a 9 to 13 percent decrease in mortality for those who increased the intensity of their exercise sessions.</li></ul>
How to Measure Exercise Intensity<p>So, how do you know for sure that you're exercising at a strenuous level? Let's look at three ways to measure the intensity of your physical activity.</p><h3>1. Your heart rate</h3><p>Monitoring your heart rate is one of the most reliable methods for measuring exercise intensity. Exercising at 70 to 85 percent of your maximum heart rate qualifies as vigorous exercise intensity.</p><blockquote><strong><strong>WHAT IS YOUR MAXIMUM HEART RATE?</strong></strong>Your maximum heart rate is the fastest your heart can safely beat. To find out what your maximum heart rate is you need to subtract your age from 220. For example, for a 40-year-old person: <ul><li>220 bpm (beats per minute) minus age</li><li>220 – 40 = 180 bpm</li></ul>To work out at a vigorous pace, you'll want to exercise within 70 to 85 percent of your maximum heart rate. For example: <ul><li>180 x 0.70 (70 percent) = 126</li><li>180 x 0.85 (85 percent) = 153</li></ul>For a 40-year-old person, a vigorous training range is 126 to 153 bpm.<br></blockquote><p>You can check your heart rate while you're working out by wearing a heart rate monitor or <a href="https://www.healthline.com/health/how-to-check-heart-rate" target="_blank">taking your pulse</a>.</p>
How to Add Vigorous Activity to Your Workout<p>Adding strenuous activity to your weekly workout routine requires some careful planning. Fortunately, many of the activities that you do at a moderate level can easily be performed at a higher intensity.</p><p>One way of incorporating vigorous aerobic activity into your routine is to do a <a href="https://www.healthline.com/nutrition/benefits-of-hiit" target="_blank">high-intensity interval training (HIIT)</a> workout. This type of workout combines short bursts of intense activity — typically performed at 80 to 95 percent of your maximum heart rate — with recovery periods at 40 to 50 percent maximum heart rate.</p><p>To sustain this level of training, consider following a 2:1 work to rest ratio. For example, a <a href="https://www.healthline.com/health/treadmill-weight-loss#hiit" target="_blank">treadmill workout </a>or outdoor running session could include:</p><ul><li>running at 9 to 10 mph for 30 seconds</li><li>followed by walking at 3 to 4 mph for 60 seconds</li><li>alternating this work-to-rest ratio for 20 to 30 minutes</li></ul><p>Playing a fast-paced sport like soccer, basketball, or racquetball is another effective way to add strenuous activity to your fitness routine. Participating in <a href="https://www.healthline.com/health/benefits-of-a-spin-class" target="_blank">cycling classes</a> or swimming laps are other ways to build more strenuous exercise into your workouts.</p>
Safety Tips<p>Before you turn up the intensity on your workouts, it's important to keep the following safety tips in mind.</p><h3>Check with your doctor</h3><p>If you have a health condition or you haven't been active in a while, make sure you talk to your doctor before you start a high-intensity exercise routine. Your doctor can advise you on a safe level of exercise or how to become more active in the safest way possible.</p><h3>Build up the intensity slowly</h3><p>Going from low- or moderate-intensity workouts to vigorous exercise requires time and patience. While you may be ready to jump in with both feet, the safest way to add more vigorous exercise is to do it in bite-size increments. Pushing yourself too quickly can result in injuries and burnout.</p><p>For example:</p><ul><li><strong>Week 1:</strong> Swap out one moderate-paced cardio session for a HIIT workout.</li><li><strong>Week 2:</strong> Swap one moderate-paced session with a HIIT workout, and also add a circuit strength training session to your weekly routine.</li><li><strong>Week 3 and 4: </strong>Repeat weeks 1 and 2 before you start adding more high-intensity exercise to your weekly routine.</li></ul><p>It's also a good idea to space out your vigorous workouts throughout the week. Try not to do two strenuous sessions back-to-back.</p><h3>Don't forget the recovery time</h3><p>Your body requires more time to recover from a vigorous workout compared to a low- or moderate-intensity session.</p><p>To help your body recover, make sure to always include a cooldown and <a href="https://www.healthline.com/health/exercise-fitness/static-stretching" target="_blank">stretch routine</a> after strenuous physical activity.</p><h3>Stay hydrated</h3><p><a href="https://www.healthline.com/nutrition/7-health-benefits-of-water" target="_blank">Staying hydrated</a> is especially important when you're exercising hard. Not drinking enough fluids can affect the quality of your workout and make you feel tired, lethargic, or dizzy. It may even lead to <a href="https://www.healthline.com/health/dehydration-headache" target="_blank">headaches</a> and <a href="https://www.healthline.com/health/pain-relief/how-to-stop-leg-muscle-cramps" target="_blank">cramps</a>.</p>
The Bottom Line<p>Turning up the intensity of your workout sessions can be an effective way of boosting your overall health and fitness. It's also an easy way to save time when trying to fit a workout into your day.</p><p>To play it safe, always start slow and pay attention to how your body feels.</p><p>While vigorous exercise offers many health benefits, it's not appropriate for everyone. If you have a health condition or you haven't been active in a while, make sure to talk with your doctor before working out at a more strenuous level.</p>
- 10 Ways to Tell if You're Dehydrated - EcoWatch ›
- Should I Exercise During the Coronavirus Pandemic? Experts ... ›
A healthy coral reef is a noisy place.
- This Robot Is Delivering Coral Babies to the Great Barrier Reef ... ›
- The Great Barrier Reef is on a Knife Edge ›
- 2020 Great Barrier Reef Bleaching Event Is Most Widespread to Date ›
By Jeffrey Miller
In January 2015, food sales at restaurants overtook those at grocery stores for the first time. Most thought this marked a permanent shift in the American meal.
Solving the Age-Old Problem of Spoiled Cheese<p>People have eaten pasta and cheese together for hundreds of years. Clifford Wright, the doyen of Mediterranean food history, says <a href="http://www.cliffordawright.com/caw/food/entries/display.php/topic_id/16/id/105/" target="_blank">the first written recipe</a> for macaroni and cheese was created in the court of the king of Naples in the 13th century, while <a href="https://food52.com/blog/9916-the-history-of-macaroni-and-cheese" target="_blank">the first reference</a> in an English language cookbook likely appeared in Elizabeth Raffald's 1769 book "The Experienced English Housekeeper."</p><p><span></span>An internet search for macaroni and cheese recipes will turn up over 5 million hits, but many still prefer to get theirs in a box – the kind with pasta that comes in shapes ranging from shells to Pokemon characters, accompanied by a packet of powdered cheese sauce.</p><p>Boxed macaroni and cheese was one outcome of the quest for ways to keep cheese longer. Some cheese gets better as it ages – a well-aged cheddar is one of life's delights – but once most cheeses hit their prime, <a href="https://www.dairyfoods.com/articles/91548-how-to-maximize-cheese-shelf-life" target="_blank">they tend to quickly go bad</a>. Before household refrigeration became common, many retailers wouldn't even stock cheese in the summer because it spoiled so quickly.</p><p>Processed cheese solved this age-old problem.</p>
When Natural Was Nasty<p>Today, food that's simple, pure and natural is <a href="https://theconversation.com/how-was-french-cuisine-toppled-as-the-king-of-fine-dining-66667" target="_blank">all the craze</a>, while <a href="https://apnews.com/c06a1200807c4b82a03452d08d480692" target="_blank">disdain for processed foods</a> is practically a credo among sophisticated consumers.</p><p>But when Kraft's different forms of processed cheese came out, they found widespread acceptance despite their strange textures. The fact that it wasn't natural didn't seem to bother consumers at all. In fact, as international food historian Rachel Laudan <a href="https://online.ucpress.edu/gastronomica/article/1/1/36/93394/A-Plea-for-Culinary-Modernism-Why-We-Should-Love" target="_blank">has noted</a>, back then, "natural was something quite nasty." She describes fresh milk as warm and "unmistakably a bodily secretion." Throughout the history of cookery, most recipes aimed to transform an unappetizing raw product into something delightful and delectable.</p><p>So for most consumers, processed foods were a godsend. They kept well, tended to be easily digestible and, most importantly, they tasted good. Many of them could be easily prepared, freeing women from spending entire days cooking and giving them more time to pursue professions and avocations.</p><p>In some ways, processed foods were also healthier. They could be fortified with vitamins and minerals, and, in an era before everyone had access to mechanical refrigeration, the fact that they kept well meant consumers were less likely to contract diseases from spoiled, rotten foods. Pasteurization of dairy products virtually <a href="https://www.the-scientist.com/foundations/rethinking-raw-milk--1918-65126" target="_blank">eliminated diseases like undulant fever</a>, while foods processed and canned in large factories were less likely to harbor food-borne illnesses that could crop up due to faulty or improperly sanitized equipment used by home canners.</p>
At least 14 people were killed when Tropical Storm Amanda walloped El Salvador Sunday, Interior Minister Mario Duran said.
- Mass arrests and overcrowded prisons in El Salvador spark fear of ... ›
- Savior or strongman? El Salvador's millennial president defies ... ›
- El Salvador: Inhumane Prison Lockdown Treatment | Human Rights ... ›
- Shocking cars submerged in El Salvador from tropical storm Amanda ›
- Tropical storm Amanda batters El Salvador | News | DW | 01.06.2020 ›
By Mark Kaufman
Some fires won't die.
They survive underground during the winter and then reemerge the following spring, as documented in places like Alaska. They're called "overwintering," "holdover," or "zombie" fires, and they may have now awoken in the Arctic Circle — a fast-warming region that experienced unprecedented fires in 2019. The European Union's Copernicus Atmosphere Monitoring Service is now watching these fires, via satellite.