Any athlete will tell you that staying properly hydrated is critical to maximizing performance.

But knowing how much to drink and when to drink during rigorous physical exercise isn’t easy. Simply quenching your thirst often isn’t enough if you’re sweating profusely, exercising in high heat or humidity, or engaging in prolonged exertion, scientists say.

Many athletes, whether competitive performers or casual weekend players, do not voluntarily drink enough water to prevent dehydration, and that can create problems ranging from fatigue and dizziness to serious heat illness and heatstroke if left unchecked.

During two hot and humid summer days in July and August, researchers with the University’s Department of Kinesiology in the Neag School of Education tested the effect of different methods of hydration on competitive runners to see how it impacted their abilities.

The goal of the study is to help create more effective hydration guidelines for athletes, military personnel, firefighters, and other individuals who are required to perform in extreme conditions and who often push their bodies to dehydration through prolonged exertion, says Professor Douglas Casa, the University’s director of athletic training education and a certified athletic trainer.

A national expert on exertional heat illnesses, Casa is the study’s principal investigator. Carl Maresh, head of the kinesiology department and director of UConn’s Human Performance Lab, and Lawrence Armstrong, an expert in physiological responses to exercise and heat tolerance, are co-investigators.

“The basic idea of this study is to compare two different hydration protocols,” says Rebecca Lopez, a fourth-year kinesiology doctoral student and certified athletic trainer who is using the hydration study as the basis for her doctoral dissertation. “There is an ongoing debate over how much athletes should drink.”

In the study, 14 runners from Storrs and surrounding towns volunteered to participate in two, 20-kilometer runs on a specially-marked trail at Mansfield Hollow State Park. The runners were told to run at their maximum pace during each trial.

Researchers calculated each runner’s “sweat rate” prior to the trials. The researchers then used that sweat rate to determine how much water each athlete should receive during their runs. Also, before each run, professors and doctoral students weighed the athletes, took their blood, checked their vital signs, and gauged their abilities in a series of balance tests.

During one trial, runners were allowed to drink “ad libitum,” taking as much of the water as they wanted, Lopez says. In the other trial, the runners were told to drink all of the water in the bottles regardless of how they felt.

At the end of each day’s run, the researchers gathered another set of physiological data for comparison purposes. Lopez says she expects to analyze the data this fall and finalize some conclusions by spring.

The researchers hope the data will help them better understand whether athletes are hydrating themselves sufficiently on their own accord, and whether some hydration methods may be better than others at reducing core body temperature and improving performance.

“Most athletes are dehydrated,” Lopez says. “At 1 percent or 2 percent loss of body weight due to dehydration, it’s not a huge deal. But when you get into 3 percent or more it can start to be detrimental to performance.”

Previous field research done at UConn with runners has shown that body temperature is 0.5˚F higher for every additional 1 percent of body weight loss. That means a person’s core body temperature could be about 1˚F higher if they are just 2 percent more dehydrated, Casa says, and this could become quite relevant for health and performance issues as the level of dehydration gets more extreme.

When a person’s body is dehydrated, the loss in fluid leads to a drop in blood volume and that in turns forces the heart to work harder to move blood through the bloodstream to the brain, skin, and muscles where it is needed, Armstrong says.

In some sports, like track and field, baseball, or tennis, athletes have easy access to water. But in other sports, like soccer, lacrosse, and distance running, staying hydrated may be more difficult due to infrequent breaks. Athletes also need to be careful not to drink too much water – a condition known as hyponatremia – which can be equally detrimental to performance and health.

Katrina Gustafson, a competitive runner from Hebron who participated in the study, says she tries to stay hydrated during her runs but it can be difficult.

“It can be difficult during races,” says Gustafson, who runs about 40 miles a week. “Most of the time, you don’t hydrate enough.”

Some of the symptoms of dehydration include: thirst, dry mouth, weakness, dizziness, confusion, sluggishness, and fainting. One common rule of thumb for staying hydrated is to drink 16 ounces of fluid to replace every pound of fluid lost to sweat. Drinking fluids before exercise or rigorous activity is just as important as drinking during and after, the researchers say.

One easy and quick way to gauge hydration is to monitor your urine color, Armstrong says. The widely-accepted urine color chart has been used in UConn research studies since 1991. If your urine volume is small and/or your urine is dark in color, chances are you are dehydrated, Armstrong says, and although some medications and dietary supplements may darken urine, this rarely invalidates the technique.

“We often tell runners and cyclists if you look at your urine and it’s pale yellow or the color of straw,” he adds, “you are probably well hydrated and your body has a full supply of water.”