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Every so often, after a marathon, headlines will pop up about a marathon runner collapsing and dying during or shortly after the race. It’s rare, but it happens: A 2025 study found records of 176 cardiac arrests during long-distance running events in the U.S. out of about 29 million people who finished the races. 

Deaths like these raise the question of whether such an intense physical feat as a marathon can possibly be dangerous, or at least unhealthy, for the heart. We asked scientists who study marathoners about long-distance races and heart health, plus what runners can do to keep themselves safe.

Is all that running actually good for you?

Experts are pretty unequivocal: Yes. “Exercise is good for the heart,” says David Oxborough, professor of echocardiography and cardiovascular physiology at Liverpool John Moores University in the U.K. “We know that regular moderate-intensity exercise improves your cardiovascular risk, it reduces mortality, and it has real positive benefits.”

Of course, training for a marathon—which can take months or years of steady increases in endurance—is different from the act of running the race itself, says Daniel Muniz, senior lecturer in exercise physiology at the University of Hertfordshire in the U.K. “Running a marathon is a big physiological stress. You're going to hurt after…and if you look at markers in your physiology, everything is going to be all over the place.” Markers of muscle damage and heart damage are elevated, at least for a little while. (Oxborough, who has studied some of these elevated markers, says that they come back down swiftly and don’t seem to be linked to long-term damage.)

But the consistent training that running a marathon requires carries positive effects for physical and mental health, Muniz continues. “The benefits far outweigh the negatives. I think that's very fair to say.” 

Why do people die running marathons, then?

Dying during a marathon is extremely uncommon, says Oxborough. What’s more, it doesn’t seem random. People who die during endurance running events tend to fall into two categories, often identified after the fact: either younger people who have undiagnosed genetic heart problems, or middle-aged men who have heart disease without any symptoms.  

“If you've got underlying disease, then there is a risk of sudden cardiac death. If you're under the age of 35, that is usually caused by an inherited cardiac disease, such as cardiomyopathy. As you go over 35, the main cause is more acquired disease, like coronary artery disease,” he says.

How can you find out if your heart is healthy enough for a marathon? And should you?

“You should, absolutely,” says Oxborough. “We do pre-participation cardiac screening for young people in competitive sport. We have charities in the U.K. It's now becoming much more accepted in the U.S., and it wasn't before. This is a simple 12-lead ECG and a questionnaire to young people.” 

That’s enough to start the process of figuring out whether people might have an inherited disease, the experts say. If they do, it doesn’t mean they have to stop training. It just might shape how they decide to train and manage their risk.

What about older people?

The problem with coronary artery disease is that many people have no symptoms in the early stages. 

If you’re thinking of running a marathon and you’re over 35 or 40, here’s what Oxborough recommends: “Go speak to your GP. Have a 12-lead ECG done. Have your blood done. Make sure your cholesterol levels are normal. Have your blood pressure taken, and if any of them show any sign that they may be a higher risk, then we recommend an exercise stress test. And if you're very lucky, if you're able to access it, a CT coronary angiogram,” he says. These are tests that will help establish your baseline and what is likely to be happening in your arteries before you really ramp up training.  

Not all of these are required, but “a baseline test of risk is really important, and that you can do at your GP,” he says.

Can anyone run a marathon?

In principle, yes. “I am of the opinion that most people with training should be able to run a marathon. The important bit there is: with appropriate training for a number of months or or perhaps a year,” says Muniz. 

This is not a physical challenge where you can go out and achieve it tomorrow without practice. “But if you start training and you start running for 20 minutes, or run and walk, and then transition to run for 20 minutes, 30 minutes, 40 minutes, and then you do that for a number of months, I think most people should be able to eventually run a marathon,” he says.

In the wet heat of a Guadalcanal afternoon on Christmas Eve 1944, two regiments of the 6th Marine Division met on a football field of packed earth and broken coral. They had come to settle a question argued over beer: Which of them had the better team? The island where the Pacific War’s first major American offensive was fought had been quiet for nearly two years, a staging ground of tents and supply depots where men trained and waited and swatted at the insects that gave the island’s Armed Forces Radio network its name. The game was a serious to-do: There were printed programs, numbered T-shirts, goalposts the Marines built themselves, and an announcer whose call went out over the Mosquito Network to men on ships and islands across the Pacific. At least 1,500 Marines lined the field, some with money on the outcome. Neither team scored. Three months later, the division sailed for Okinawa, an island on Japan’s doorstep, where 15 of the 65 men who played that day were killed. 

That game is the short reprieve at the heart of Peter Berg’s The Mosquito Bowl, in select theaters Oct. 30 and arriving Nov. 25 on Netflix. Directed by Berg, who wrote the screenplay with Mark L. Smith, the film adapts Pulitzer Prize-winning journalist Buzz Bissinger’s book and follows four of those players from the Saturday afternoons when the best of their lives still seemed to lie ahead, through weeks of training that could not prepare them for what came next, to one of the bloodiest battles of World War II. Nicholas Galitzine plays John McLaughry, alongside Tom Francis as Dave Schreiner, Bill Skarsgård as Bob Bauman, and Ray Nicholson as Tony Butkovich. Three of those men would die on Okinawa. The fourth would live to 90.

The stadiums give way to boot camp, boot camp to the reef at Tarawa, Tarawa to the long crossing toward Okinawa, where the familiar idea of victory becomes a contest with no whistle, no clock, and survival as the only trophy. What the film is after, once the pageantry is stripped away, is that moment of recognition: young men who thought they had been sent to win learning what they have really been sent to do.

Berg has made films (and a massively popular TV show) about football and films about war. Here the same young men must do both. “They got out there and very quickly found that it wasn’t a game,” Berg tells TIME. “They weren’t really qualified for it, but they were going to do their very best. The tragedy is the death of that innocence.”

The lives before the uniforms

What the four men shared, after Japan attacked Pearl Harbor on Dec. 7, 1941, was an assumption. Their country had been attacked, and young men like them were expected to go to war.

Schreiner, from Lancaster, Wisconsin, had twice been named an All-American in his career with the University of Wisconsin; in 1942 he was named the Big Ten’s most valuable player, and the Detroit Lions drafted him. The letters he left behind, now at the Wisconsin Historical Society, show a more private side of the star athlete. He was engaged to Odette Hendrickson, wrote to her and to his parents constantly and judged himself without mercy. “Tightly, tightly woven,” Bissinger says of the man. Francis found in him a care and a vulnerability that colored everything, and a mind that would not rest. “He overthinks everything, but then as soon as one of his brothers comes to him and isn’t quite there, he just can find a way to be like, ‘I’ve got you,’” the actor says.

Schreiner had options. “Dave could have gotten out of it because of who he was,” Bissinger says. “He could have easily been a phys ed instructor somewhere at one of the bases in the United States, and he said, ‘No, I got to go. My friends are going. I’m just sitting around doing nothing, and I can’t live with that.’”

The man who kept Schreiner loose was his teammate Bob Bauman, a tackle from Harvey, Ill. Bauman’s father died when he was a boy, and he grew up holding his family together. “Bob was more happy-go-lucky,” Bissinger says. When Schreiner tightened up, Bauman’s advice, as the author renders it, came down to a single line: “Dave, don’t overthink, Dave.” The two enlisted within months of each other and would serve in the same company.

Butkovich was the son of Croatian immigrants who settled in a coal town in central Illinois. He played two seasons at Illinois before the Marines sent him to Purdue, where he rushed for 833 yards in seven games in 1943. The team went undefeated, but the Marines called him away before the season ended, and he cried in the locker room over having to go. The Cleveland Rams made him a first-round pick in 1944, and he kept up a pen-pal correspondence with a 9-year-old fan. “He was really on this high level,” says Nicholson of Butkovich’s stature as a football star. “But at the same time, he was a mama’s boy.”

The oldest of the four, McLaughry was the only one already out of college. His father, Tuss McLaughry, coached at Brown, and John captained his father’s team in 1939 before playing a season for the New York Giants. He also painted. “Steady, solid, almost a Renaissance man,” Bissinger says. Galitzine was drawn to both McLaughry’s intellect and his artistic sensibility. He and Berg discussed McLaughry’s “ability to intellectualize things and how that kind of dissipates, given the trauma and the grotesque violence that he sees,” the actor recalls. What remains is a sense of duty more immediate than politics. “The loyalty you have really is not even to your nation necessarily, or to the men who send you to war, but it’s to your brothers who are in the foxhole next to you,” Galitzine says.

By the autumn of 1944, the war had brought all four to Guadalcanal. Though the film has them all in the same regiment, in reality, Schreiner, Bauman, and McLaughry were officers in the 4th Marines, and Butkovich served in the 29th, the other regiment on the field that Christmas Eve.

The game they made for themselves

Bissinger first learned of the Mosquito Bowl by chance, through a passing mention he found while working on another book. “It sounded ludicrous to me and totally unimaginable,” he says. A program survived, with both teams’ rosters, and then he learned that all but one of the men on them had since died. The lives behind those names emerged from what their families had kept: letters, report cards, pictures drawn in childhood.

The game stemmed from an argument. The former college players in the 29th were sure they could beat the former college players in the 4th. The rosters held three All-Americans, seven former captains, and close to 20 men who had been drafted by NFL teams or would go on to play in the league. By December, the regiments had drilled for months, and the drilling had gone stale; men were getting antsy, Bissinger says, and antsy men “get this thousand-yard stare.” The division’s commander, Major General Lemuel Shepherd, was looking for a way to lift their spirits. “When morale flags, Marines get worried,” Bissinger explains, reconstructing the general’s reasoning. “They preoccupy themselves with death, and we need some diversion.” Shepherd approved the game, and the Marines worked hard to make it resemble the real thing. “This was about joy,” Bissinger says. “It was about doing something that they loved, that for many of them would be the last thing they would ever do that they loved.”

Little of the game itself survives: the date, the printed program, a few photographs, and a final score of 0-0. The men wore T-shirts and cut-off dungarees. Nobody stuck to the intended mode of touch football for long, and the coral in the dirt drew blood. What matters about the Mosquito Bowl is not anything that happened on the field but that it happened at all, an afternoon in which the war paused and these men got to be what they had been raised to be. “The football of it all never really mattered. I think it wasn’t about who scored what, what tackle here, who had this many rushing yards,” Berg says. “It must have given them an opportunity in the middle of this descent into hell to stop, to get out of hell, to be free again, to be young again, and just play a game. That’s what kind of hooked me on Buzz’s book, and that’s what we tried to recreate.”

In the film, the game plays as a respite, beautiful and painful at once: everything they get back is exactly what the war will take. Most of the plays are lost, and Berg is untroubled by it. “I don’t even know what the score of the game is in our movie. I truly don’t know,” he says. “You ask me who won. I don’t know. Was it a tie? I think so. Did they have fun? Yes.”

There would be no rematch. On March 15, 1945, the division sailed from Guadalcanal, by way of the Navy anchorage at Ulithi, for Okinawa.

What Okinawa took

On the morning of April 1, 1945, Easter Sunday, the Americans came ashore on the western beaches of Okinawa, 350 miles south of mainland Japan, in the largest landing of the Pacific War. The defenders did not meet them at the beaches; they had dug into the ridges and limestone caves of the island’s southern third and waited. The 6th Marine Division swept north, cleared the island’s northern reaches in three weeks, then turned around and marched south.

The rains came in late May, and for days they did not stop. The roads dissolved, supplies went forward on men’s backs, and the wounded came back the same way. The terraced hills were cut with caves and family tombs the Japanese had turned into firing positions, so that an advance of a few hundred yards could last an entire day of sealing holes with dynamite and flame. Civilians hid in the same caves the soldiers fought from, and many died in them too. By late June, more than 12,000 Americans were dead or missing and nearly three times as many wounded. The Japanese defenders, told not to surrender, mostly did not. The Okinawans are the ones no one can count; estimates of the civilian dead run from about 94,000 to more than 140,000. The Cornerstone of Peace at the island’s southern tip carries more than 240,000 names, soldiers and civilians from every side, and names are still being added.

The worst of it came at a hill the Marines called Sugar Loaf. It stood only some 50 feet high, but it sat between the division and Naha, the island’s capital, and Japanese guns covered it from three directions. It changed hands again and again, and in the 10 days before the Marines finally held it, on May 18, more than 2,600 men from the division were killed or wounded. Three days before the hill fell, George Murphy, the former captain of Notre Dame, who had played in the Mosquito Bowl the previous Christmas Eve, was leading a platoon of the 29th Marines on its slopes.

As Bissinger tells it, Murphy was ordered to make another assault and protested. “We don’t have enough hand grenades,” he said. He would fight for his country, but this was a death assignment. “The captain said, ‘I don’t give a sh-t. You got to go up there,’” Bissinger says. The Army’s official history of the campaign tells it slightly differently. In that version, it was Murphy who asked to fall back and his captain who refused: the hill was to be held, whatever the cost. Murphy brought his men down anyway, through the mortar smoke. He stopped for one of the wounded on the way, and a fragment killed him there. Only 11 of his platoon’s 60 men were left. Bissinger, who refused to soften the book’s combat, puts it plainly: “War is not about glory. War is not about heroism. War is about death.”

Butkovich had been dead for a month by then. He was killed on April 18, during the division’s push through the north of the island. He had been on Okinawa less than three weeks. He was 24, the first of the four to die.

Bauman and Schreiner were still paired up. On the morning of June 4, the 4th Marines landed from the sea on the Oroku Peninsula, southwest of Naha. Bauman had been wounded in April and returned to the front. On June 6, his captain went forward with a scouting party, and Company A of the 4th Marines was Bauman’s to lead. He did not lead it long: a Japanese machine gun on the high ground nearby opened fire, and Bauman was killed. Schreiner, a platoon leader in the same company, had two more weeks to live.

There is no agreed-upon account of Schreiner’s final patrol. By June 20, the Japanese defense had collapsed into the island’s southern tip, and the Marines were clearing the last pockets of resistance there. Schreiner was mortally wounded on patrol. Accounts collected by Terry Frei, a chronicler of Schreiner’s Wisconsin team, differ on how: some cite grenade fragments, others a sniper or Japanese soldiers who appeared to surrender before opening fire. He died the following day, June 21, as the battle was drawing to a close. Japan announced its surrender less than two months later. McLaughry, whose platoon of self-propelled guns was supporting Schreiner’s battalion that day, was told at the time that a sniper had shot his friend, and later heard that the bullet had lodged in his spine.

McLaughry fought through all of it and lived. He came home to his wife, raised three children, led the football programs at three colleges, the last of them Brown, and kept painting, but the war stayed with him.

Bringing the men back

Bissinger never met any of the four, though his father, a rifleman in the 4th Marines, fought on Okinawa and never talked about it. “Can you make guys come alive you’ve never met, and never will meet?” he says. He is candid about how he chose them to tell this story: “I picked those people because they had the most readily accessible material.” The McLaughrys kept everything, down to letters John wrote at 4. Schreiner had a niece. Butkovich had a cousin, still living when Bissinger was writing. “Tony had really nothing, so I compiled as much as I could,” he says. “But I felt he had to be in there, particularly since he was the best of the football players.” Their stories reach only as far as their families, and the war, allowed.

The book found its way to the screen through family. Berg and Bissinger are cousins, and The Mosquito Bowl is the second of Bissinger’s books Berg has adapted, after Friday Night Lights. The book follows a wide cast of Marines through several battles; a two-hour film could not, and Berg took his cuts to its author. “I presented my kind of outline to Buzz. I’m like, how would you feel if I did this?” he recalls. “He thought about it, and he said, ‘Do it.’” The film takes dramatic license in places, including a grudge between Schreiner and Butkovich and a battle at Tarawa, the bloody November 1943 assault on a Pacific atoll, where none of the four fought; Marines stranded on a reef under fire was the first image Berg knew the film had to contain. “There were some areas in which Pete had to create his own narrative, and that was going to veer from the book. But that doesn’t bother me, because the essence was there,” Bissinger says.

Berg found his own way in on the ground. He walked Okinawa’s battlefields with Marines stationed there, and came away ready to write.

On set, Berg gave up some of the control a director usually keeps. “I like not being in complete control and allowing something to grow out of that,” he says. Filming in Australia, that meant a director who kept noticing terrain no one had checked. Wildlife handlers cleared the ground before the actors lay in it, Galitzine says, because the local snakes could kill. Berg would look past the cleared area to some unvetted cliff and announce that the actors should climb it. “We just did it,” Galitzine says. Crawling through the Australian bush made the four actors feel as though they were on an adventure together. “It really was an exercise in trust, in a lot of ways.”

Berg had never shot anything like the reef landing. The production put stuntmen, then actors, then camera operators into heavy Australian surf. “You can drown in that surf,” Berg says. “They call that ‘washing machine.’ You’re in the ‘washing machine.’ Think about doing that while you’re being shot at.” Elsewhere, a sand quarry near the coast stood in for the battlefield below Shuri Castle, the Japanese command post at the heart of the island’s defenses. Production designer Philip Ivey scattered scorched books, broken dishes, and clothing across it, the wreckage of ordinary life. The resulting film is intimate and enormous at once, the camera close enough to see fear, with cutaways from the ground to the planet itself that set the men’s suffering inside a scale too large to take in.

In the editing room, the question became how much football the film needed. Early versions spent considerably more time on the game. The finished film instead begins with McLaughry after his experience in combat, before going back to the men’s football years. “The football is there to serve a purpose, and that’s to illustrate that these men were living it up. They were at a good spot in their lives,” Berg says. “So I felt like we needed just enough football to tell that story, and then move on.” The actors trained for much more than made the final cut. Before cameras rolled, they spent weeks in training that was part football practice, part Marine boot camp, each actor drilled at a position, enabling the production to make limited use of stunt doubles.

Four actors, four men

Each of the four actors went looking for the man he was playing, and each found him somewhere different. Francis found his in a joke. The Mosquito Bowl was his first film, and early in the shoot he went to Skarsgård with a stage actor’s questions: Where do I look, what do I do, how do I make it all happen? Skarsgård’s answer was, “You’re overthinking, Schreiner.” Francis heard the character in it. “I was like, this is the man,” he recalls. Skarsgård leaned on the one fact that set Bauman and Schreiner apart from the others. They played beside each other at Wisconsin, joined the Marines a few months apart, and went to war together. “Tom can always come to me and lean on me, and I could always come to lean on him, both as actors, but also as our characters,” Skarsgård says. “The way that they worked was that Bob could pull Dave out.”

Nicholson found his in letters. He read Butkovich as a performer whose confidence was real and whose tenderness ran underneath it. “Once they go through this experience, that version of Tony Butkovich is forever gone,” he says. A five-page handwritten letter Nicholson sent Berg, one the director calls among the “most beautiful” he has ever received, showed him the passion he was casting for. Butkovich’s letters to a young fan, meanwhile, gave the actor a way into the man. Nicholson wrote letters of his own to his father, actor Jack Nicholson, who would have been about that boy’s age during the war. “How do you be someone’s hero?” he asks. “What is that like?” Purdue also sent him restored film of Butkovich with the ball. By chance it came on the anniversary of Butkovich’s death, and Nicholson watched it by himself with the lights off, feeling as if the two of them had somehow met.

Skarsgård went to the place itself. While researching the role, he spent three days on Okinawa with Marine guides, and at the end he asked them to take him to where Bauman was shot. It is in Naha now, a residential neighborhood with a playground and a convenience store. “I’m standing where he took his last breath,” Skarsgård recalls, describing the “immense amount of responsibility” he felt. He was struck by the unlikely connection between his own life and Bauman’s. “Here I am, a Swedish actor, 80 years after this happened, and I’m thinking about this man, and I’m connected with this man, and I feel just so much gratitude towards him.”

Galitzine carried a different weight, the survivor’s, and it came into sharper focus toward the end of filming. The production shot the last scene for Nicholson, Francis, and Skarsgård on a boat, and when it was done, they wrapped and he did not, because McLaughry’s story continued. “There was just this underlying sense of dread, for a lot of the movie, and guilt,” he says. He had spent months alongside the three actors, “knowing that they were going to have to say goodbye in a way that I didn’t.”

The lives that remained

Late in The Mosquito Bowl, in a scene Berg wrote, Schreiner talks with McLaughry on a secluded beach about having children and what a man might leave behind. “The contrast of being in one of the most beautiful places I’ve ever been, and then thinking about Dave going through that thought process, it was almost like an out-of-body experience,” Francis says. Galitzine, playing a version of McLaughry beginning to unravel, says that in the scene Schreiner helps “crystallize the reason why they’re doing what they’re doing,” and that Francis’s portrayal gave him “something larger than the chaos and the brutality.”

Schreiner never had those children. Bissinger keeps a photograph of him on his wall, and when he looks at it, he reaches for a word he acknowledges is probably not the right one: waste. “Here was a life that really should have been lived,” he says. “He should have had kids. He should have been married. He should have had a career. He should have had laughter. He should have had glory. He should have had disappointment. All the things that we have in life, and he’s never going to get that.”

The film frames the four men’s lives with a warning and a number: the Herbert Hoover line it opens on, about old men declaring wars the young must fight, and the loss it closes on, 75 million dead worldwide. Berg wants the audience to leave carrying both. “That wasn’t that long ago,” he says. “We live in a very violent planet today, and I really hope that never happens again. I don’t think a movie can change that. But taking a personal responsibility for each and every human being to think about how we can prevent people from having to go kill each other. If we can, let’s do it.”

Against that death toll, four men may seem like nothing. Yet the enormity of the war begins to register through the three lives it cut short and the one it forever changed. Of the dead, traces remain: Schreiner’s letters, Bauman’s snapshots, and restored footage of Butkovich running with the ball. The war left a fuller record of these men than ordinary lives would have, had they simply been allowed to go on living them uninterrupted. Had Schreiner come home, his handwriting might never have left Lancaster.

In the few photographs of the game, young men in T-shirts stand on the makeshift field, the jungle a dark line behind them. For one afternoon on Christmas Eve 1944, nothing was decided. Nobody lost.

McLaughry grew old with the years his friend never had. Then, in 1993, nearly half a century after Okinawa, he wrote out what he could remember of the day Schreiner was hit, a man in his seventies setting down what a young officer had seen, heard, and been told. Much of what he knew had reached him secondhand, and he doubted the version that had settled into the record. He returned to it all the same, because he was the last of the four men who could, and because somewhere on a field of coral in the flat afternoon light, with the ball sailing through the air, the other three were still 23, and in that borrowed moment, always would be.