Sweat science: MLB players, teams devise methods to stay cool as temperatures rise

New York Times

11 hours ago

In between innings on the mound, Tampa Bay Rays starter Ryan Pepiot disappears into the dugout tunnel and parks himself near a portable air conditioning unit prepared for the right-hander's arrival.
He places his pitching hand inside a device designed to cool his body's core temperature. With his left hand, he hydrates. First he sips from a bottle that is 'very salty and doesn't taste great,' he said. After the first out is recorded, he switches to a more appetizing mixture that includes DripDrop electrolyte packets.
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Pepiot developed this routine last summer. It has become even more imperative with his team spending this season playing in the sweltering humidity of Tampa's George M. Steinbrenner Field. He used to finish the two bottles every four innings. Now he estimates he is consuming nearly twice as much.
'They've had to make extra ones for me this year,' Pepiot said.
Unlike the other major North American sports — and European soccer — baseball plays the heart of its season under the summer sun, putting it in a uniquely difficult position as those summers continue to get hotter. As June now turns to July, baseball players across the country are dealing with different versions of the same question: How do you stay cool in this heat? Or, more to the point, how do you keep playing without cramping and vomiting?
There are devices like the CoolMitt and regular hydration tests. There are precise instructions for how to consume liquids. There are ways to train your body to prepare for the elements. But sometimes, the best approach is the simple one: 'Drink as much water as possible and pray to God it's enough,' Rays starter Drew Rasmussen said.
The heat has begun to make its mark on this season. Cincinnati Reds shortstop Elly De La Cruz vomited in the outfield on a 96-degree late June afternoon in St. Louis. A day later, Detroit Tigers starter Casey Mize exited an outing in Tampa while suffering from cramps. The Atlanta Braves visited Citi Field last week in the midst of an East Coast heat wave that saw temperatures surpass 100 in certain parts of New York. A video board in the New York Mets clubhouse featured an illustration of a droplet with a two-word admonition: DRINK WATER.
That was what Braves starter Spencer Schwellenbach did before facing the Mets a week ago Monday in the teeth of the heat wave. He hydrated 'way more than usual,' draining four or five bottles of water in the morning before flooding his system with sodium tablets and electrolytes at the ballpark. With the temperature hovering in the mid-80s that night, he logged seven scoreless innings.
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'I was peeing, like, every 30 minutes,' Schwellenbach said. 'It was unbelievable. But during the game I felt good.'
The next day, with triple-digit heat before the game and a 97-degree first pitch, Mets outfielder Tyrone Taylor pointed to a Vitamin Water bottle with a pinkish hue sitting in his locker. The drink came courtesy of Jeremy Chiang, the club's performance nutrition coordinator. The coloring came from a hydration packet called Right Stuff. During the game, Chiang packed individual coolers of these drinks for each player. 'We get a lot of reminders just to drink a lot of water and take those,' Taylor said.
The state of athletic nutrition has advanced to the point where teams can test players for hydration levels, measure the rates at which they sweat and devise specific plans for each individual. They can replace fluid and electrolytes with specialized drinks designed for each player, and they can bring down elevated body temperatures with ice baths and frozen towels.
'In baseball, it only takes being a little proactive to overcome it because you have opportunities to cool and to drink and to be in shade, especially at the pro level,' said Douglas Casa, CEO of the Korey Stringer Institute and one of the leading experts on heat management for athletes. 'It has to be more than taking a sip of fluid. It has to be meaningful.'
In the not-so-distant future, Casa said, teams might have a dugout iPad showing each player's real-time hydration level — eventually, their body temperature, too — but even then, it will be imperative that teams prepare ahead of time. Casa said he worries first about a player's pregame hydration level — it's hard to make up ground, especially in difficult conditions — and he stressed that there is no one-size-fits-all strategy for addressing it.
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The Mets provided a series of guidelines for making it through last week's games. Not every suggestion made sense for every player. Mets starter Clay Holmes said he did not require cold towels in between innings. 'I don't really like getting, like, more wet,' Holmes said. 'I try to dry off a little bit.' The training staff advised players to build a base of cool liquids in the morning and consider taking a cold shower in the evening. During the games, the players were told to consume five to eight ounces of liquid every inning, even if they weren't thirsty. Chugging was not recommended.
That might have been what went wrong for De La Cruz. After getting thrown out at the plate in the bottom of the third inning on June 21, he 'drank a bunch of water — I mean a bunch,' Reds manager Terry Francona said after the game. 'He went right out and got rid of it.'
Mize, who lives in Tampa during the offseason, could not discern a similar cause for his own heat-related issues. 'I feel like we're pretty buttoned up, man,' Mize said. 'I drink half my body weight in ounces of water every day.' He embarked on his usual routine before his outing against the Rays: He ate a banana before the game and three more during it. A plethora of Gatorade, water and cold towels could not prevent his body from locking up with cramps after five innings.
'Get me out of Steinbrenner Field, I guess,' Mize said.'That place is rough.'
In deference to the facility's lack of a roof and the instability of south Florida weather, Major League Baseball front-loaded Tampa Bay's schedule with home games this year as Tropicana Field undergoes repairs for damage sustained during Hurricane Milton. The Rays will play at Steinbrenner Field only 16 times in July and August. On Monday, the team welcomed the Athletics, the other club using a minor-league stadium as its home ballpark in 2025.
The issues at Sutter Health Ballpark in Sacramento are well-documented, as Athletics pitcher Luis Severino relayed to The Athletic this past weekend: Sparse crowds, a lack of air conditioning, minimal cover from the sun during day games. The Athletics plan to play in Sacramento through at least 2027. By then, the organization hopes, construction will be complete on a new stadium in Las Vegas. The design plans released by the team describe the Vegas ballpark as 'climate-controlled,' with a roof to ward off the hellish desert sun.
In the meantime, designated hitter Brent Rooker said, the days in Sacramento may be tough, but at the very least, the temperature at night has been tolerable.
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'Honestly, it hasn't been too bad at home,' Rooker said. 'What we've found at Sac is no matter how hot it has been during the day, it cools down a ton at night. So the night games have been, generally, fine.'
The same cannot be said for the humidity in Tampa.
Experts refer to something called the WetBulb Globe Temperature, which the National Weather Service describes as 'a measure of the heat stress in direct sunlight, which takes into account: temperature, humidity, wind speed, sun angle and cloud cover.' It's basically the WAR of heat — an advanced metric reducing multiple factors into a single number. FIFA has introduced guidelines calling for additional mid-game cooling breaks when the Wetbulb temperature exceeds 32 degrees Celsius (a little over 89 degrees Fahrenheit) — they have been a regular feature at this year's Club World Cup — and American football teams and long-distance runners have also become familiar with the Wetbulb concept while working with experts like Casa to keep athletes from overheating when the measurement gets too high.
Baseball isn't as fraught as soccer and football, largely because each half-inning provides an opportunity for players to cool and hydrate. (In fact, Casa said he worries at least as much about the umpires who do not get regular breaks and often — ahem — are not in professional athlete shape.) It's imperative, Casa said, that players begin each game fully hydrated, replace lost fluids in-game, and keep their core temperature well shy of the 104-degree extreme danger zone. Each player handles heat differently, and simply cooling by a degree or two, Casa said, can improve physical, emotional and cognitive function.
Or, more to the point: it can keep a player from puking in left field.
'That's why these people are making the effort,' Casa said. 'Like the Tampa Bay Rays, they're making the effort to figure it out because of the individual variability.'
The Rays understood the elements would be unkind this season. The training staff recommends players drink tart cherry juice, beet juice and water mixed with a recovery pack called Juven. During spring training, the Rays tested each player's sweat rate — second baseman Brandon Lowe discovered that he was a 'Tier 2 sweater' — and Pepiot tried to acclimate to the heat by taking his dog on longer walks. The players try to spend time outside before games, 'so when it's time to go to work, I'm not getting kicked in the teeth because I've been sitting in the air conditioning all day,' Pepiot said.
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The group has responded to the challenge. The team entered Monday trailing the New York Yankees by only a half game in the American League East. Tampa Bay has a winning record at home. Several Rays suggested those early months at Steinbrenner Field have prepared the club well for future heat waves this summer.
'It kind of seemed like a curse,' Rasmussen said. 'But maybe it was more of a blessing in disguise.'
On Saturday afternoon, as the temperature at Baltimore's Camden Yards inched into the 90s, there were Rays swarmed across the infield for optional pregame fielding drills. The team had grown comfortable being uncomfortable.
'We're used to it now,' Pepiot said. 'We're playing outdoors in Tampa, Fla. It is not cool at all.'
With reports from The Athletic's Cody Stavenhagen
(Illustration: Will Tullos / The Athletic; Photo: William Purnell / Getty Images)