Last Tuesday a group of leading sports scientists gathered in Northern England to watch the NBA Finals.

That wasn't the intended reason for the gathering. The idea was for top trainers and scientists, from teams like the Premier League's Southampton and Manchester United along with England, Scotland and Welsh rugby clubs, to hear from Michael Young, noted expert from the Athletic Lab. They wanted to learn what the latest research said about keeping highly paid athletes healthy and at their competitive best.

But the two-day workshop was overrun with talk of, and concern for, LeBron James. The worry begins with a baseline level of "stress" -- that's their term -- surrounding all NBA players. Sports science has exploded in recent years with evidence that factors like mucked-up sleep, air travel and densely scheduled games put players in jeopardy. The NBA is elite in all categories.

"It's unfathomable to go across the country from Cleveland to San Francisco -- at the very least a five-hour flight -- and then play 50 minutes in a game the next day," Young says. "You don't see that in any other sport. The travel stress alone can be debilitating.

"And then you add to the fact that basically it's a one-man team at this point, and the mental and physical burden -- it's just overwhelming," Young says.

Young remembers watching Game 3 while the trainers geeked out over the stamina of James, who was coming off two straight overtime games, including 50 minutes in Game 2. This was the party where people were dying to know LeBron's heart rate variability scores -- measuring his bodily stress levels. There was speculation about his OmegaWave outputs, a measure of neurological fatigue.

But mostly they just wanted to know how he could keep going at all.

By Thursday, James was discovering his limits. At halftime with his Cavaliers facing a 12-point deficit in Game 4, coach David Blatt blared toward his seated players like a suited lieutenant on enemy lines, hammering into them that there were only four games left "of their playoff lives."

"Lay it out there!" he screamed. "'Til you're done!"

Done came sooner than the Cavaliers had hoped. It was fewer than three minutes of play until the starting point guard asked to sit. James played the ensuing quarter but could barely move by the start of the fourth. He rested a bit as the Warriors went on a run. When he returned, he was no longer authoring an epic Finals performance. The Warriors took turns, it seemed, ripping the ball from his hands or tipping away his shots.

"I gassed out," James conceded after a fourth quarter with zero points. The Cavs lost by 21 at home.

As it turns out, the Cavs' bodies were just about cooked at halftime. Exhaustion is the toughest opponent James and his teammates face in the Finals.

And the science makes it clear: The NBA's program of bunching so many games so closely together combines with coaches' go-hard mentality to create a potent cocktail of injury risk.

"I can't think of another scenario quite like this where the turnaround times are so fast and there's so much travel," Young says. "It really is pretty crazy."

Science is uncovering fascinating lessons about fatigue. For example, rugby players exhibited faster recovery times after wins compared to losses. And sleep deprivation can cause humans to be effectively drunk after a snoozeless night. The more you play, the more your injury risk skyrockets.

In one study, European soccer players who played more than one match a week reported a higher injury rate than those who did not.

And flying is a problem. In the Premier League, players are never required to take flights longer than an hour. Studies show that long-distance travel that crosses time zones can have serious effects on muscle recovery.

Keep in mind, the NBA Finals schedule requires players to play three games in five days. And that's after an 82-game season and another three series of seven-game sets.

Other researchers have found that 10 minutes a week is, for most people, the threshold for maximum-effort jumping and sprinting. After that, performance declines and injuries mount.

"Having dealt with stress levels in our training of elite athletes, we all know that LeBron has to be absolutely shot," Young says. "There's something to being able to work through the fatigue, but that has its limits. And you really open up the window for injuries to start occurring."

"You just don't tough through it," Young says. "That notion is very antiquated."

Ronald Martinez/Getty Images

About the time of Blatt's halftime tribute to ignoring exhaustion, ESPN's Sage Steele asked NBA commissioner Adam Silver what could be done to reduce injuries in the NBA.

The obvious answer would seem to be to reduce the number of games -- something some NBA insiders say owners would never consider, as it could cut into revenue.

Silver made the insiders look prophetic, suggesting injury risk "was not about the length of the season." Instead, he says the league is looking into shuffling around off days to reduce regular-season back-to-back games and spells of four games in five nights. "We're working on that," he said. At other times he has mused about elongating the season slightly, and under his watch the NBA has stopped his predecessor's practice of fining teams for resting players.

It's fitting that we often see trainers massaging James' legs on the sidelines like a pit crew, because James himself treats his body like a Formula 1 race car.

LeBron's Recovery Acts Here's a sample of the rigorous routine LeBron

employs to get his body ready between games: Tuesday night (after the game) Recovery stretching Cold tub Rehydration Wednesday (off day) 30 minutes on stationary bike Breakfast Rehydration Cavaliers Practice Cold tub Massage Stretching Muscle stimulation 3-hour nap Stretching with specialized equipment Massage Cryotherapy Dinner Thursday (Game Day) Repeat Wednesday's process before game

Led by longtime personal trainer Mike Mancias, the four-time MVP's 24-hour recovery program has minute-by-minute treatments that are microtuned to get the most use of his available time. For instance: James recently installed a cold tub in his Akron, Ohio, home so he can save the trip to Cleveland. This summer, James and Mancias located a liquid nitrogen cryotherapy chamber nearby, and James frequents the facility on off days to prep his body for the annual 100-game grind.

And yet, despite all the round-the-clock precautions, his body is waving a white flag, pushed past the brink.

This is what happens after five straight Finals runs at the height of the sport. After three consecutive Finals appearances at the prime of his career, Michael Jordan left the sport and took the year off. Jordan retired after his second trio of Finals trips. Perhaps knowing this, James took a two-week break in January to ready himself for the arduous Finals road.

At 30, James has already played more NBA minutes than Larry Bird, Magic Johnson or Allen Iverson.

In Game 3, James rested on the bench for only 12 minutes and 41 seconds of real time, and just two minutes of game action, according to ESPN video tracking. The rest of the night, the 260-pound James was on his feet, leaping, colliding, sprinting, exploding, falling, rising and slaloming all over the 94-foot court.

Just 12 hours later at practice, James limped to the podium and could barely keep his eyes open as he addressed the media.

"You guys can see I'm not getting much sleep right now," James said. "It's been a difficult challenge, a tough challenge, but I knew that. Being the sole leader of a team and a franchise, it's taxing."

He needed IV fluids that night.

Two days later, Blatt played him 41 of the first 45 minutes of Game 4. Somewhere in the middle of that, he needed glue to patch up a head wound after smashing into a TV camera. Veterans with championship experience, Mike Miller, Shawn Marion and Kendrick Perkins all looked on from the bench.

"We haven't played many guys throughout this playoff run," James said.

In a calendar year during which stars like Kevin Durant, Paul George, Kevin Love, Kyrie Irving, Carmelo Anthony, Serge Ibaka, Wesley Matthews, Jabari Parker, Dwight Howard, Chris Bosh and Dwyane Wade battled overuse injuries of various degrees, James is still standing.

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The star of the Finals so far is the player charged with guarding James: the Warriors' Andre Iguodala. At a time of year when almost every player appears to be conserving energy, Iggy races the floor with abandon, relishing physical confrontations, like the chance to elevate and hammer-dunk over someone on the fast break.

He's also a player steeped in sports science, who has banned screens from his bedroom and wears a sleep monitor that feeds data to a laptop. His coach, Steve Kerr, deliberately benched Iguodala for games at a time during the season specifically so he'd have fresh legs at the end of the season. Part of the reason Kerr brought him off the bench was because the schedule demanded it.

"That's a big part of it," Kerr said. "We tried all season long to give Andre rest. We gave him four or five games off at key times, and we just wanted to keep him as fresh as possible."

AP Photo/Ben Margot

A photo of James hangs in a wooden frame on a wall inside the trainer's room of Premier League soccer club Liverpool FC (James is a part owner), one of the most successful clubs in competitive sports. Stars like Steven Gerrard and Raheem Sterling glance at him as their heart rate variables are monitored, presumably pleased they don't have to do anything like what the NBA asks of James.

Playing 40-plus minutes multiple times a week while traveling across the country and carrying the offensive load?

"That's the top of the top," Young says. "Every one of these NBA guys are under a tremendous amount of stress at this point, but LeBron in particular, playing 46 minutes a game with that travel and quick turnaround ... it's a little insane. That's unbelievable, really, to bear that mental and physical burden and still play at a high level."

When asked whether there is any athletic equivalent to playing two games in three days while traveling across three time zones, Young paused for a moment to think. He could point to only one.

"Maybe the Tour de France," Young says.

But even that, Young attests, can't quite capture the carnage on James' body.

"In cycling, there's no physical impact on your body like basketball," Young says. "The overall workload is significantly higher on the Tour, but there's no constant impact, which plays a huge role in fatigue that LeBron is probably experiencing. And there's no real travel to speak of."

Young and his sports science peers are watching the Finals closely. They've seen every caliber of athlete. And nothing compares to James and the workload he's asked to do now in the Finals.

"Unfathomable," Young says.