Was it hard to concentrate during that long meeting? Or, does the crossword seem a little tougher? You could be mildly dehydrated.
A growing body of evidence finds that being just a little dehydrated is tied to a range of subtle effects — from mood changes to muddled thinking.
“We find that when people are mildly dehydrated they really don’t do as well on tasks that require complex processing or on tasks that require a lot of their attention,” says Mindy Millard-Stafford, director of the Exercise Physiology Laboratory at Georgia Institute of Technology. She published an analysis of the evidence this month, based on 33 studies.
How long does it take to become mildly dehydrated in the summer heat? Not long at all, studies show, especially when you exercise outdoors.
“If I were hiking at moderate intensity for one hour, I could reach about 1.5 percent to 2 percent dehydration,” says Doug Casa, a professor of kinesiology at the University of Connecticut, and CEO of the Korey Stringer Institute.
For an average-size person, 2 percent dehydration equates to sweating out about a liter of water.
“Most people don’t realize how high their sweat rate is in the heat,” Casa says. If you’re going hard during a run, you can reach that level of dehydration in about 30 minutes.
And, at this level of dehydration the feeling of thirst, for many of us, is only just beginning to kick in. “Most people can’t perceive that they’re 1.5 percent dehydrated,” Casa says.
But, already, there are subtle — maybe even imperceptible — effects on our bodies and our mental performance.
Take, for example, the findings from a recent study of young, healthy and active women who agreed to take a bunch of cognitive tests, and also agreed to restrict their fluid intake to no more than six ounces for one day.
“We did manage to dehydrate them by [about] 1 percent just by telling them not to drink for the day,” says Nina Stachenfeld of the Yale School of Medicine and the John B. Pierce Laboratory, who led the research.
The women took one test designed to measure cognitive flexibility. It’s a card game that requires a lot of attention, since the rules keep changing throughout the game.
“When the women were dehydrated they had about 12 percent more total errors” in the game, says Stachenfeld.
She repeated the tests after the women drank sufficient water, and their performance improved. “We were able to improve executive function back to normal — in other words— back to the baseline day — when they rehydrated,” the scientist says.
Dehydration didn’t hamper performance on all the tests; the women’s reaction time, for example was not impeded. The decline was seen during thecomplicated tasks.
Though the study was small, and funded by PepsiCo, which sells bottled water, Stachenfeld designed the methods and completed the analysis independently. And other scientists say her findings fit with a growing body of independent evidence that points to similar conclusions.
“I absolutely think there could be big implications of having a mild cognitive deficiency with small amounts of dehydration,” Casa says.
If you’re a student, for example, a 12 percent increase in errors on a test might matter. And whether you’re a pilot, a soldier, a surgeon or a scholar, many daily tasks depend on the ability to be precise and pay attention.
For anyone trying to do their best work, the findings raise a number of questions:
How much water do we need?
There are no exact daily requirements, but there are general recommendations.
A panel of scholars convened several years ago by the National Academies of Sciences, Engineering and Medicine concluded that women should consume, on average, about 91 ounces of total water per day. For men, the suggested level is even higher (125 ounces).
Note that this total includes water from all sources, including food and other beverages, such as coffee and tea. Typically, people get about 20 percent of the water they need daily from fruits, vegetables and other food.
Also, water needs vary from person to person. For example, body weight and muscle mass matter. Also, physical activity and heat exposure can increase the amount of fluid a person needs.
How can you tell if you’re dehydrated?
One easy test: The color of your urine is a good guide. As a general rule of thumb, the darker the color, the more likely you are to be dehydrated. Aim for shades that have been described as “pale lemonade” or “straw.” A color chart developed by physiologist and University of Connecticut professor Lawrence Armstrong can be a helpful guide, researchers say.
Are older people more vulnerable to dehydration?
As we age, we’re not as good at recognizing thirst. And there’s evidence that older adults are prone to the same dips in mental sharpness as anyone else when mildly dehydrated.
Don’t wait until you’re thirsty. A good rule of thumb is to sip fluids throughout the day. No need to chug huge amounts at one time; there are some risks to overhydrating, too.
Can coffee, tea and other caffeinated drinks have a dehydrating effect?
The most recent evidence finds that coffee provides similar hydrating qualities to water. In other words, yes, your morning cup of joe — or whatever caffeinated beverage you fancy, can help to keep you hydrated.
As we reported in 2014, people who routinely drink coffee or tea develop a tolerance to the potential diuretic effects of caffeine.
Most states rank poorly on heat safety for their high school football players. Too many teens have paid the price, and temperatures are only getting worse.
JUL 20, 2018
Laurie Giordano had just arrived after her son collapsed on his high school football practice field in Fort Myers, Florida.
It was June 29, 2017, and she remembers it with painful clarity.
The Riverdale High School teammate who knocked on her car window at the end of a sweaty practice, telling her that her son couldn’t get up on his feet. Her son, cradled in a coach’s arms, making a slow, repetitive moaning sound, while players poured water in his mouth. The coach saying the player was just a little overheated.
The ambulance arrived, but 10 days later, Zach Martin-Polsenberg, a 16-year-old lineman, was dead, a victim of heat stroke. In the ambulance, Zach opened his eyes a few times and squeezed his mother’s hands, but that was the last of their communication.
Through her grief, a shocked Giordano tried to figure out how this could have happened and concluded Zach’s high school had not taken the potential for heat stroke seriously.
So she spent the last year trying to convince Florida authorities to tighten their heat-safety rules. Giordano shared Zach’s story with the leadership of the Florida High School Athletic Association, but she was only partly successful; the association bucked its own medical advisory committee by voting to “strongly recommend,” but not mandate, a first-aid tool experts say could have saved Zach’s life—a cooling tub, water and some ice.
“I felt like I couldn’t just sit in my grief and have it happen again,” Giordano said. “I don’t think I could live with that, knowing that I hadn’t done anything to try to make for change.”
Heat stroke can occur in all states. But researchers studying student athletes, especially football players during summer workouts, see more of it in the East, and particularly the Southeast, where sweltering temperatures, high humidity and intense sunshine make for a trifecta of deadly risk, and where high school football is very popular. These weather conditions are only getting worse as the climate changes, bringing more heat and humidity.
Just as coastal cities brace for rising seas and communities and farms look for ways to manage heavier rain, there’s an increasing awareness that adapting to climate change includes protecting people from heat, including young athletes. Yet a new ranking of states by their heat safety measures for youth sports shows that many states are failing to require simple precautions that could save lives.
“Heat is already a major safety hazard for athletes and the broader public,” said Andrew Grundstein, a University of Georgia professor of geography and climate science. “Yet we should still be able to do the activities like sports that we enjoy. Considering that our climate is warming, it is even more important that we have heat safety guidelines and policies. This will help us adapt and be more prepared for the more frequent hot conditions.”
Summer Days Are Getting Hotter
Since 1995, three football players a year on average have died of heat stroke, most of them high schoolers, according to the National Center for Catastrophic Sport Injury Research, which tracks football injuries and deaths. In the last five years, the average was about two—still too many when these deaths are avoidable.
Max Gilpin, a 15-year-old, was overcome by heat during an August football practice in 2008 at his Louisville, Kentucky, high school. There was no cooling tub there, either, recalled his mother, Michele Crockett.
“This was preventable,” said Crockett, who advocates for football safety through the Max Gilpin Beat the Heat Fund.
“What our family went through was horrific,” she said. “He struggled for three days in the hospital. We watched all that. We watched as his organs shut down. I never saw him regain consciousness again.”
Grundstein has been studying the impact of extreme heat on high school football for several years. He and his fellow researchers have identified the players most at risk of heat stroke—the largest ones—and studied the most dangerous practice weather based on a more sophisticated way of measuring heat.
Developed for the military, certain kinds of heat stress monitors now recommended for high school football practices take into account temperature, humidity, wind speed, sun angle and solar intensity instead of merely temperature. Heat stress monitors also go beyond the commonly used “heat index,” which factors in temperature and humidity to provide the “feels like” temperature numbers commonly used by forecasters and weather apps.
Southeastern states, Grundstein said, already experience 40 to 60 days when heat stress factors can become extreme enough for schools to stop outdoor practices—roughly a heat index of 103 degrees. In the next 20 to 50 years, Grundstein expects an additional 30 days of these conditions in the Southeast, with other parts of the country also affected, but to a lesser yet still significant degree.
“Almost the whole country is going to see a lot more of these days in the summer, and they will extend into the spring and fall,” Grundstein said. “In the long term, we are going to see more hot, humid days that are going to pose a hazard to athletes.”
Since the 1980s, nationally, “it’s been steamrolling upward, and the story is not different than that in the Southeast. If you look at the Southeast now, since the 2010s, it’s actually the warmest period on record.”
As global warming continues, Kunkel said, the Southeast’s temperatures will rise.
Hydration Is for Survivors
Football’s tradition for tough summer workouts despite heat and humidity was described in a 1975 commentary, “Dog Days and Siriasis—How to Kill a Football Player”, in the Journal of the American Medical Association, by Dr. James P. Knochel of Dallas. An archaic term for heat stroke—siriasis—came from the expression “the dog days of summer,” or the time of the year when the dog star, Sirius, rose in the morning with the sun, Knochel wrote.
It was not uncommon, according to the JAMA commentary, to deny players water or to give overweight lineman diuretic pills to help them lose weight by ridding their bodies of needed water and salt.
Wearing full protective gear and helmets in the heat would also toughen up the players, the coaches’ believed.
“People thought hydration was for weaklings,” said Michael F. Bergeron, an expert on exercise-heat stress who has advised the International Olympic Committee and the Federation of State High School Associations. He recalled a scene in the 2000 movie “Remember the Titans” in which the coach played by Denzel Washington tells a player that “water is for cowards.”
Hydration helps maintain blood flow to muscles, vital organs and the brain, and assists in sweating, which cools the body, Bergeron said. But in hot, humid weather, sweat does not evaporate very well. So people cannot release as much heat through sweating and are at greater risk for dangerously overheating. Well hydrated athletes can still overheat “if the activity is too hard, for too long, especially while wearing too much uniform and protective gear,” said Bergeron, the senior vice president of SIVOTEC Analytics, a sports technology and analytics company.
Heat stroke, with a rectal temperature greater than 104 degrees and other symptoms, can cause the brain or other organs to swell, possibly resulting in permanent damage or death, according to the Mayo Clinic.
These High School Policies Can Save Lives
If cooling tubs can now be considered climate adaptation, so can other heat-safety recommendations from the Korey Stringer Institute at the University of Connecticut, named for the Minnesota Vikings football player who died from heat stroke in 2001
The institute conducts research and education on how to keep athletes, soldiers and laborers safe from sudden death, including heat stroke.
Last year, the institute published its first health and safety state rankingsfor high school athletes. The institute’s experts believe all high school teams should follow certain policies in categories such as sudden cardiac arrest, brain injury and heat, and its rankings are based on whether those recommendations are followed.
When it comes to heat, the institute wants coaches to ease players into summer workouts, limit the use of full gear and the duration of outdoor practices on hot days, and provide three hours of air conditioned breaks when two practices are held in the same day. It stresses the importance of life-saving cooling tubs by allotting three points out of 20 total possible points for states that mandate their use, and it gives more points for heat stress monitors.
Heat stress monitors, which cost around $100 to $200, are “the gold standard” and reflect conditions on the practice field, said Samantha Scarneo, vice president of sport safety for the institute. The tubs are the most effective way for teams to bring down body temperature, limit damage and save lives, she added.
“Without a doubt, cold water immersion has a very good cooling rate compared to other previously studied cooling methods, and it is the most feasible,” she said.
The Rankings: States and Heat Safety Measures
Using the institute’s latest state-by-state safety data, updated on July 19, InsideClimate News separated out the heat scores and ranked states accordingly.
North Carolina, Hawaii, New Jersey, Utah, Georgia and Kentucky came out on top. Texas, Washington, New Mexico, California, Colorado and New Hampshire were at the bottom.
Thirty-six states received less than half the maximum heat-safety points. Only 12 states require cooling tubs, and only six require heat stress monitors.
Georgia, a state that had been considered a leader with its response following a series of heat deaths several years ago, made for a perplexing case. Cooling tubs were first required by the Georgia High School Athletic Association in 2012, and a checklist that goes to coaches includes that. But it is unclear if the measure was ever enforced. Steve Figueroa, a spokesman for the association, said the requirement was left out of its main rulebook and only reinstated recently after InsideClimate News raised questions about it.
The rankings rankled some state associations and their National Federation of State High School Associations, which criticized last year’s study as incomplete and flawed by what they saw as a one-size-fits-all approach. “There has never been a time that coaches, athletic directors and school administrators were more focused on risk minimization,” the federation said.
Still, the federation acknowledged “room for improvement” and said schools need more funding.
States that don’t like the rankings tend to be the ones that haven’t scored as well, said Julian Tackett, commissioner of the Kentucky High School Athletic Association. “Anything that brings awareness is good,” he said.
Grundstein said heat safety policies are important but should reflect regional differences.
In the Deep South, players get used to really hot conditions, and that can help them during practices, he said. In northern states, student athletes can be less able to tolerate intense heat because they’re not as accustomed to it, he added.
A Dangerous Loophole: Summer Practice
Max’s death in Kentucky prompted officials there to make heat awareness training mandatory for all coaches and players—something Florida only required this year after Zach died.
Scarneo, of the Korey Stringer Institute, says Florida has had four high school football deaths from heat since 2010, the most for any state. The Institute wanted the Florida High School Athletic Association to mandate heat stress monitors and cooling tubs, too, she said.
So did the state association’s own medical advisory committee.
“We were a little surprised that the board wasn’t accepting of our recommendations,” said Robert Sefcik, executive director of the Jacksonville Sports Medicine Program, a nonprofit that advocates for youth sports injury prevention, and a member of the advisory committee. That the association “strongly recommended” heat stress monitors and cooling tubs was a step in the right direction, he added.
Kyle Niblett, spokesman for the Florida High School Athletic Association, would not answer questions about why the association’s board of directors had rejected its medical advisory committee recommendations.
Sefcik said association officials were worried that they didn’t have legal authority to mandate the purchase of cooling tubs or heat stress monitors and had questions about enforcement and liability. Niblett would only say in an email that the association will inform member schools of all heat safety precautions before fall practices are set to begin on July 30.
That date brings up another Florida controversy.
The association leaves heat safety up to county school districts for summer practices, held before July 30. Zach was in a summer practice when he developed heat stroke.
“It’s a huge loophole,” Sefcik said.
He said surveys suggest more than 95 percent of Florida high schools have cooling tubs already. But that doesn’t mean they always use them.
Zach’s high school is an example of that, he said. “The school did have an immersion tub, however it was in the locker room and not accessible either because it was out of sight or out of mind,” Sefcik said. “Nobody thought to utilize it.”
Zach’s family has submitted a notice of intent to sue the School District of Lee County. Giordano said the family is weighing legal options.
Because of potential litigation, district spokesman Rob Spiker said he was limited in what he could say. But he said Lee County schools will be using cooling tubs and buying heat stress monitors.
That’s a start, Giordano said. She is now working with Florida lawmakers to tighten up statewide heat safety rules that were punted by the association.
“I am frustrated they didn’t do more,” she said. “Even if Zach had lived, we would still be doing this. There is no way he would have let this go by without saying we need to do something. He was a protector.”
It’s 90 degrees and humid outside. The last thing you want to do is workout in this temperature – but did you know that training in the heat could actually work to your advantage?
A couple weeks ago, I had the opportunity to visit the Mission Heat Lab at the University of Connecticut campus in Storrs, CT. The lab is open to anyone – everyday Joe’s and athletes alike – all you have to do is reserve a time to visit.
In the lab is a heat chamber that can be set to up to 110 degrees, and the humidity set between 10 and 90 percent. Inside the chamber, you can hop on one of the bikes or treadmills which will track your heart rate, core temperature, body mass, wattage, pace/speed and sweat rate. All of these factors are then used for sweat electrolyte and sodium balance tests, which can tell a person the amount of electrolytes he or she loses at a particular temperature, going a specific wattage, for a set amount of time.
“For athletes, they can set the temperature and humidity to match specific race conditions,” explains Robert Huggins, PhD, ATC, vice president of research and athletic performance and safety at the Korey Stringer Institute at the University of Connecticut. This would allow, for example, a triathlete to set Kona, Hawaii-like conditions so that they test in the same environment in which they’ll be racing.
“Using the electrolyte test, which involves sweat weight before and after, and a distilled water washdown to remove electrolytes to back calculate the concentrations, we can give recommendations that the athlete would need for that race based on the amount [of weight and electrolytes] they lost during the test.” That number can then be taken and used to help map out proper hydration and fueling for a longer race if need be.
Since I’m obviously not a professional athlete, I was just curious to find out my sweat rate running in the heat for a half hour. By taking an ingestible core body temperature sensor pill, which wirelessly transmitted readings to a recorder device outside my body, measuring my weight before and after the test, and exactly how much water I drank during the heated run, I was able to learn that I lose .74 liters per hour. That means that at that same temperature, if I were to run an hour, the perfect amount of fluid I should be taking in would be .74 liters because that’s how much I was sweating out.
Running in the heat for that long didn’t seem all too daunting at first, but by the end, I was so sweaty that I was counting down the minutes for it to be over. But I learned that when done safely, working out in the heat is actually very beneficial.
“With as little as five to seven days of training in the heat, and keeping your core temp between 101.5 to 103.0 with proper hydration for 60 minutes, you can achieve lots of benefits,” explained Huggins. Achieving this stabilization of core temperature and proper hydration is often called heat acclimatization.
“From a physiological standpoint [with heat acclimatization], your heart rate is lower at a given intensity, and blood volume expands allowing you to deliver more blood to the exercising muscles and to the skin for cooling via sweat,” Huggins said. “Most importantly, your core temperature is lower both at rest and during exercise and your body becomes a more efficient sweater.” And, he explained, if you can push heat training up to 10 to 14 days consecutively, you can also hold onto electrolytes and fluids better. Overall, you can become a more efficient athlete by sweating more efficiently, adjusting to the heat and maximizing your use of electrolytes.
For most athletes or people who exercise three to five times per week, it can take about two to three sessions of training in the heat for someone to feel more comfortable moving the body in hot conditions. But each person is different – some may take a full week depending on their fitness level. “In general, the more aerobically fit you are, the quicker you get used to it,” explains Huggins. “Once you achieve heat acclimatization, or ‘Heat Acc’ for short, in order to hold onto the benefits of the adaptations your body has made, you need to continue to exercise once every five days in the heat.” However, even after achieving Heat Acc, “if you go 10 to 14 days without exercising in the heat, a majority of those adaptations will be lost,” Huggins adds.
Of course, it’s easy to track your core temperature in a lab like the one I was in. For everyday athletes who don’t have access to a lab, the only way to accurately track your core temp – to be sure it’s in the correct range without spiking to an unsafe level – is to take your temperature rectally. That would mean pausing your run, bike or workout to get your temperature – not exactly ideal, or likely to happen.
The good news is you can track your sweat rate to find out how much fluid you’re losing when you exercise for a certain amount of time in a particular environment. Simply step onto a scale with a full water bottle before your workout, then work out and drink the water, and when you finish, step back onto the scale. The difference in your weight is your sweat rate or how much fluid you lost.
For athletes looking to improve performance, or for those who are just trying to stay hydrated on that next summer trail run, this could be a game changer. “If you’re having fueling issues, whether it’s over or under hydrating, this is a great way to hone in on that and figure out exactly how much fluids your body needs in specific conditions for a specified amount of time,” Huggins concludes.