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Dr. Diandra: The ins and outs of driver hydration

Fans at Nashville Superspeedway may struggle to keep cool in temperatures projected to be in the 80s. But for NASCAR drivers, staying chill is just one more part of their weekly training routine. Each driver has a slightly different approach.

“I’m a wimp,” Todd Gilliland said, “I’ve been wearing (a cool shirt) everywhere since the beginning of the year and I’ve got a cool box.”

Daniel Hemric told SiriusXM’s “The Morning Drive” that part of his training included playing golf in the heat.

SCORCHER AT NASHVILLE: Cup drivers battle heat Sunday

You’ll hear all kinds of strategies: cool shirts, cool boxes, ice bags, water bottles, exercising in the heat, saunas… some drivers even have personalized hydration programs.

A whole hydration program sounds like overkill. David Ferguson, Associate Professor of Kinesiology at Michigan State University, assures me it’s not. Proper hydration gives drivers a performance edge.


Credit: Michigan State University

You might wonder how a Ph.D. -- the author of academic papers like “Vivo-morpholinos induced transient knockdown of physical activity related proteins” -- becomes an authority on racecar driver hydration.

For Ferguson, it was a series of coincidences. The first was seeing a NASCAR race on television. Jeff Gordon’s debut made him want to drive racecars. Except…

“I was basically too old and too poor,” Ferguson said. “At 18, I decided I’m going to go to medical school and become a surgeon. Then I can afford my race cars later in life.”

He attended a track day in Las Vegas where the temperature rose to 116 °F. Ferguson complemented the driver who had been second fastest for the day.

“The driver was like ‘what are you talking about?” Ferguson recounts, “There are three cars in front of me.’ He was so dehydrated that he’s actually seeing triple.”

Ferguson wondered why, with all the effort that goes into engineering race cars, no one engineers drivers. A masters degree in exercise physiology at the University of North Carolina – Charlotte followed. He graduated just in time for the 2008 recession to eliminate his first motorsports job before he even started it.

So Ferguson returned to school and earned a doctorate from Texas A&M. Michigan State hired him to pursue research on how early-life nutrition influences cardiovascular development. But when he arrived, the construction of his lab was behind schedule.

That gave him time to pursue his other research interest: motorsports.

The dangers of dehydration

Your core body temperature is the temperature of your internal organs. They prefer to operate at around 37 degrees Celsius (98.6 °F), but can deal with a rise of about one degree Celsius — about 1.8 degrees °F. Ferguson measures core body temperatures using a pill the driver swallows. The pill sends him core temperature readings via a Bluetooth signal.

A rise in core temperature causes your body to sweat. Liquid on your skin evaporates, pulling heat away.

Sweat comes from the fluid in the cells in your vascular system. When you lose fluid, Ferguson said, “it’s like oil in your engine. Bad things are going to happen.”

Those bad things start with getting thirsty — the first indication you’re dehydrated. Because you’re low on fluid, your body can’t produce enough sweat to cool itself. If you don’t replenish fluids, your temperature continues to rise.

“So 38.5 °C (101.3 °F) is ‘I’m thirsty, I’ve got a headache,” Ferguson said. “And then 39 °C (102.2 °F) is ‘I’m kind of dizzy, kind of confused.’” Muscles cramp or fatigue.

Once your body realizes that sweating isn’t cooling you, it switches to trying not to create any more heat. That means shutting down any body function not essential to survival. You may pass out.

The real danger starts if your temperature continue to rise.

“If your core temperature reaches about 41 °C (105.8 F),” Ferguson says, “the body actually thinks you’ve got a really bad virus.”

The body generates heat because heat kills viruses. That’s why you run a fever when you get the flu.

Now your temperature goes up — exponentially.

“You’ll very quickly hit 45 °C (113 °F),” Ferguson said, “And we need to be at the emergency room. Now.”

In addition to monitoring core body temperature, Ferguson quantifies hydration by testing the specific gravity of the driver’s urine. That’s a quantitative analog to determining your hydration level by looking at the color of your urine.

A special patch collects driver sweat, because everyone perspires differently. Measuring ion concentration in the sweat tells Ferguson how many electrolytes the driver is losing. And, of course, weighing the driver before and after the race determines net fluid loss.

Hydration programs

Hydration is extra important for racecar drivers because they work in enclosed, hot spaces where safety equipment covers every square inch of skin. They’re often so focused on racing that they might not even realize they’re getting dehydrated.

Ferguson recommends drivers drink 10 milliliters of water per kilogram of body weight two hours before the race. That’s roughly two teaspoons for every pound of weight. A 150-lb driver would fill his pre-race hydration bottle with 20.5 ounces of water or a sports drink formulated to enhance hydration.

But the driver’s not done when he climbs into the car. Most drivers drink from a water bottle or drinking system under caution or while pitting.

“They’ll grab the straw, chug, chug, chug, chug,” Ferguson said. “You’re getting fluid in. It’s better than nothing. But it actually expands the stomach and slows water getting out. You’re not actually getting the benefits of replenishing.”

Proper in-car hydration requires the driver to continuously replenish fluids. That means an in-helmet drinking system — and getting in the habit of using it throughout the race.

“We’re going to tell you to drink at key intervals,” Ferguson said, “whether it’s every time you pass start-finish, or we may put a light on your dash to remind you or maybe an auditory tone in the earpiece.”

After the race, the driver should repeat the pre-race hydration, even if they don’t feel thirsty.

“You cannot over-hydrate,” Ferguson said, “You’ll just pee out the fluid.”

Hydrating early and often

I’ve never understood why drivers start hydrating days before the race. Water drunk on Thursday is long gone by Sunday.

“If they start dehydrated,” Ferguson explained, “they’ll release antidiuretic hormones. All these hormones try to retain water. So when you do give them water, they’re actually going to bloat and be uncomfortable.”

That’s the physiological reason for starting well before reaching the track. But there’s a psychological reason as well. Staying conscious of water intake helps the driver build positive hydration habits. That’s especially important with the Next Gen car.

“It’s definitely going to be hot,” Alex Bowman said, “but I think that’s what we all train for and all expect. Cup racing in the summer is a very uncomfortable environment, and the Next Gen car has made that environment way more uncomfortable, but just have to keep training. I think that stuff pays off, and hopefully, I’m on the right side of that.”

The pee question

No driver hydration discussion can be considered complete without talking about drivers having to pee in the car during a race.

“Where drivers get into trouble,” Ferguson said, “is they just think, keep taking it on, keep taking it on, like a liter every hour, go sit in a hot environment and drink a liter per hour. Then you are going to pee a ton.”

A driver who is otherwise in good health, and who correctly hydrates shouldn’t have to pee in the car. One more reason for the crew to encourage the driver to stick to his hydration program.