Is this the beginning of LeBron James' end?

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IF THERE'S A LOW POINT of LeBron James' career, you could make a case for Game 5 against the Celtics in the 2010 Eastern Conference semifinals. James is 25, in his athletic prime, coming off the ninth-best season in PER in NBA history to that point -- the only players to have done better being named Wilt and Michael. Expectations are supernatural. Instead, everything this night fits a pattern of "general lameness."

In a normal contest, LeBron dunks over opponents the size of Paul Pierce with ease. On this night, he's holding the ball for several unproductive seconds, burning clock, failing to conjure plans, firing bailout passes to the far corners. A man who averaged almost 30 points on the season makes only three shots all night. Almost every jumper is short. LeBron's performance -- the Celtics cruise to a 120-88 win -- will be bizarre enough to launch media-consuming conspiracy theories about undisclosed injuries and off-court distractions of all kinds. Perhaps you've heard a few.

But what if there was a simpler explanation? What if James was just ... exhausted?

In the years since, what's becoming clear to scientists and many coaches is that "general lameness" is a likely result of overwork. Consider: On that day in 2010, James was wrapping up seven seasons in which he'd played 25,197 total minutes. It's been nearly 20 years since any other player has done the same. By the 2015 playoffs, one of the high priests of biometric science, Athletic Lab's Michael Young, would declare James' workload "unfathomable," perhaps greater than any other athlete in any other sport.

This preseason, Cavs coach Tyronn Lue talked about managing James' minutes, as LeBron's coaches long have. The team even bragged about a cutting-edge system that sorts players into red, yellow and green categories of fatigue. But the Cavs struggled and failed to win the East, and James ultimately led the NBA in minutes per game.

Now more than ever the Cavs need James to walk on water because by every rational analysis, the team is toast -- loser of 15 of its last 26 regular-season games and having entered its first-round series with only a 3.7 percent chance of taking the title, according to the Basketball Power Index Playoff Odds. So the question of the playoffs becomes: Is James too fried to be his best when it matters most? With a title hanging in the balance, I sought the answer.

DR. MICHAEL JOYNER leads a Mayo Clinic lab that studies "how humans respond to various forms of physical and mental stress during activities such as exercise." He has worked with everyone from elite marathoners to NASA and the Department of Defense. He is, in many respects, the perfect person for the first question I pose to experts in a Slack group chat: Is LeBron fried merely by attempting to play 90-plus games a year?

Soon after I post it, Joyner emails: "This is complicated ...," he writes, offering that there are five factors of fatigue: 1. travel/sleep/recovery, 2. minor injuries, 3. season duration, 4. number of hard efforts (games) in a two-week window, 5. mental grind.

When we connect by phone, Joyner announces he's live from the Portland, Oregon, airport, where he's been advising a Nike-funded effort to break the two-hour marathon. There's excellent espresso at PDX, and I immediately sense that Joyner has enjoyed a cup or three. He's talking so fast, making such expansive connective ideas, that I'm reminded of a scene from Homeland in which fictitious CIA agent Carrie Matthiesen snorts powdered caffeine. I scribble on a stack of index cards as he talks, struggling with the pace, using both sides. I run out before the 15-minute call ends. It all looks like this ...

Artificial intelligence for schedule makers would be good ... three games a week ... extend season a week or two, eliminate preseason ... if I were Adam Silver I'd make two or three models of different comparisons of how recent years could have gone, get some really smart nerds on it ... no more back-to-backs, no more four-in-five ... hard workouts in season? A lot of moving parts, depends on the person, but if you have three or four days off, maybe.

The gist, Joyner says, is this: One of Le­Bron's biggest challenges is that he asks his body to do truly hard work -- all-out effort, sustained high heart rate, ending in sweaty exhaustion -- more times than most elite athletes can handle. "A good rule of thumb is five really hard efforts in two weeks," he says. "Make me NBA czar and I would shoot for no more than five games in a two-week period with no back-to-backs. That makes the regular season about 33 weeks."

In other words, if players received proper rest, that 82-game regular season would last as long as the current regular season and playoffs combined.

MY ESPN COLLEAGUE Brian Windhorst has been covering James since high school. Who better to ask about how LeBron's approach to injury prevention has changed? "When LeBron was a springy 18-year-old, he didn't even tape his ankles regularly," he says. "But now he invests hundreds of thousands per year on his body." Windhorst reveals this fun tidbit: James has his own system of liquid nitrogen tanks to apply supercool cryotherapy to inflamed joints, and a black Mercedes Sprinter van with custom white leather lounger seats, in part to allow him to receive treatments on the go. On Slack, Brian writes that the days of acting invincible are over:

It's a nearly annual event for him to come into training camp with the goal of reducing his minutes. And sure enough, after he looked exhausted in the 2011 Finals and the Heat lost to the Mavs, his minutes per game declined from 38.8 in 2011 to 35.6 in 2016.

That trend has reversed this season. He's on pace to play the most minutes since 2013-14. LeBron and the Cavs have said this was by design, that James believed it would benefit him by playing more minutes to get into premium condition before tapering later in the season. But that hasn't happened -- as the Cavs faltered he's averaged more minutes in March than November. To make matters worse, the Cavs typically ride him when he plays the second night of back-to-backs, when he averages more minutes than he does with one or two days' rest.

Last season, LeBron averaged a career low in minutes and a career low in playoff minutes heading into the Finals. It stands to reason this contributed to Games 5-7 in the Finals, when he played perhaps the finest three consecutive games of his career.

FOLLOW ANY MARATHON training program and you'll be bombarded with science-based insight about how the most dramatically wrong way to train is to run 26 miles every day. Just working out more is the kind of thinking a middle school gym teacher might rightly offer a couch potato -- even the most elite training programs advocate multiple easy days every week. Since another one of my ESPN colleagues, Tom Haberstroh, has turned the science of all of this into his beat, I reached out to him on Slack: How do you manage LeBron?

I want more LeBron, not less. So I'd argue he should play less now. Seems backward! But I look at a guy like Isiah Thomas (the Piston, not Celtic), who was an ironman ... until he wasn't. Isiah never took days off, playing more games through age-31 than any player in NBA history before him. He finished his NBA career at 32 when his Achilles snapped. Then I look at Tim Duncan, who has the most DNP-Rests in history and played until 40. If I could choose the Isiah path or the Duncan path, I'm going Duncan every time.

THERE ARE, IN FACT, people who can support the Duncan way with data. A small but growing number of experts keep databases of NBA injuries. And when I reached out by phone to one injury analyst -- who spoke on condition of anonymity for fear of losing work he does for the league -- he said something mind-blowing: The NBA has a 100 percent injury rate. Every NBA player, he said, is injured now, or will be if he keeps playing long enough. You might imagine that a player who went 50 or 100 healthy games had acquired a body that had adjusted to the league. "No," says this guy.

"Every game they don't get injured brings them closer to their next injury."

SO IF AN ATHLETE is working out too hard, how can you tell? For that, I turn to Steve Magness, who has been called a "mad scientist" for his work as an elite performance coach, exercise physiologist and the co-author of the forthcoming Peak Performance: Elevate Your Game, Avoid Burnout and Thrive With the New Science of Success. On Slack, Magness wonders whether the NBA mishandles rest out of neither economics nor stubbornness but rather "conceptualization."

I don't think people understand fatigue. Most of us walk around thinking fatigue equals tiredness. We think of it as a relatively acute situation. Throw a little rest at it and we'll be fine. Or just "tough" your way through it. When the reality is, your performance can show very subtle signs of fatigue much earlier than you give away. As fatigue occurs, we all have compensation points. So our total performance might be pretty close to maximum, but we start getting there in slightly different ways. Watch an 800-meter runner at the end of a race: To maintain speed in the phase of fatigue, he might start swinging his arms through a bigger range of motion, or try to lift his knees a bit more.

The same occurs in basketball. At the end of the fourth quarter, to run up the floor, I won't run in the exact way I did in the first quarter. I put my body through slightly different ranges of motion, I use slightly different muscle fibers. My Achilles might not work as well as a spring in the fourth quarter, so to jump and land I might have to use more of my quads or calf muscles to generate the power to jump up for that rebound.

With each change, injury risk goes up, as my body's not relying on option A to get the job done. It's falling to options C, D and E. Our "last resort" options aren't as well-trained, so they are more susceptible to failure.

OF COURSE, IF YOU WANT TO KNOW about the state of LeBron's health, you'd want to reach out to the trainers he's worked with. But Le­Bron runs a tight ship. Miami-based trainer David Alexander, former Tim Grover employee and current Cavs employee Mike Mancias, former Navy SEAL and movement analyst Donnie Raimon and former Cavs trainer Max Benton all refused comment for this story. So we don't know about his blood values, optical tracking trends or force-plate measurements. Even his precise weight has long been a closely held secret.

"We know [players are] not at 100 percent with this schedule. How great would [LeBron James] be at his full maximal potential, fully rested?" Cheri Mah, research fellow at the UCSF Human Performance Center

Here's what we do know about LeBron, though: We know his travel schedule. He's frequently airborne at 1 a.m., crossing time zones, sleeping in airplane seats and getting up for shootaround the next morning. And now we've entered the bailiwick of Cheri Mah, a research fellow at the UCSF Human Performance Center who advises elite athletes on sleep habits. Based on her data, she says, the NBA schedule's days are numbered. "They're going to have to do something. It's not built to be sustainable long-term if they're not smart about how they play the athletes. At a certain point, you clash so much something terrible is going to happen."

The "clash" she's noting is between what the science suggests and what the schedule demands of players.

LeBron can be as sophisticated as he wants, she says, with fancy vans and other "recovery modalities." But "he still can't totally hack his need for rest. He's still going through these time zones. He can't escape the need to recover." The effects are noticeable short-term and only build over time. As Mah notes: "Stay awake for 17 hours and your reaction time is impaired equivalent to the level of legal intoxication." On Slack she explains:

Bottom line, you've got to charge up your batteries every day through various recovery modalities. If you charge up only 60 percent, you're going to run out of fuel a lot faster than if you charged up 100 percent every day, especially over the long season. As for LeBron, I'd opt to prioritize increasing rest opportunities leading into playoffs to maximize chances of a successful title run. We know they're not at 100 percent with this schedule. How great would he be at his full maximal potential, fully rested?

IT'S A STUNNING BACKDROP, 11 feet high by 22 feet long, so blue it nearly glows, and covered with iconic logos. It's stored most of the year at NBA offices in Secaucus, New Jersey, where they have several. But on April 7, a week from the playoffs, NBA commissioner Adam Silver stands before this version in an ornate faux-Beaux Arts Manhattan hotel conference room. Looking as skinny and tired as ever, in gray pinstripes and trademark metal-rim glasses, Silver addresses the media after two days of meetings with the NBA's most powerful body and the only one with the power to reduce the number of games in an NBA season to deliver LeBron and other stars to the playoffs in top condition: the board of governors.

Before the meeting, LeBron and several Cavs teammates had been held out for a Saturday night ABC game against the Clippers that would go on to tie for the lowest-rated NBA game ever on a broadcast network. In the wake of that, Silver sent owners a memo, later leaked, that sitting players would be the topic of an upcoming meeting.

It was no secret that LeBron was at the center of this conversation, but Silver manages to never once actually use the word "LeBron" as he outlines the owners' tepid thoughts on addressing the issue of rest. Instead, Silver announces that the owners have agreed that if players have to be rested, it would be best to rest them at home -- presumably on the logic that lost ticket and beer sales would hit the bottom line of the resting team's owner -- and that teams should not rest multiple players at a time in nationally televised games. Silver reiterates that next season's schedule, which has a reduced preseason and an extra calendar week of season to reduce the density of games, also might help.

He says owners did not consider reducing the total number of games.

Dancing on the head of a pin is hard; Silver is dancing on both sides of the head of a pin. He has to sell the little changes the NBA is making and leave open the idea that the league might well make huge changes in the future -- both ideas that embrace emerging science -- while also arguing that its current schedule is reasonable and not undermined by research. All this, even though the NBA employs a staff, led by Harvard-trained statistician Jason Rosenfeld, that's three years into diving into the data on rest and injuries. Outside the NBA, consensus is easy to find among scientists that few athletes if any can perform at a high level on the schedule the league asks of Le­Bron. The league has presented no doctors, or other experts, to publicly or even privately declare the current schedule optimal.

Silver uses the phrase "complex issue" three times. Asked whether he thinks it would be good for the NBA if LeBron and other superstars played fewer minutes, as Spurs stars do, he offers little clarity: "Many of our coaches have pointed out that as disappointing as it is for any individual fan on a night where a player is rested, I think if we all came to the point where we accepted the science, the medical data supports genuine resting as improving performance and prolonging careers and reducing injuries, I think we'd all have to agree that it does make sense at certain points in the season to rest players." And then comes the kicker: "Anyone listening to this, send your scientific reports into the league office. We really are trying to get a better handle on this."

In other words, LeBron might wait the rest of his career for the owners to change the structure of the game in a way that will save him from himself.

LEBRON JAMES OFTEN SAYS that he's "not even supposed to be here," which is a nod to the impossible odds that a poor kid from an itinerant single parent in and around Akron would ever become a millionaire hundreds of times over. He has learned to fly on the wings of extraordinary competitive drive. It's insane to think such a person would ever be a global leader in sitting out.

The coach who might have delivered him to April in peak condition by sitting him more probably lacks the juice to do so. The owners who could make the schedule line up with the science of human limits lack the conviction to rest someone who is so phenomenally good for ratings.

And so here we are, with LeBron in the playoffs overworked, underslept and over-traveled -- a victim of his astonishing popularity. He was so good at becoming the best basketball player in the world that maybe this season, or another one soon, the preventable will become inevitable: He'll have exhausted his superhumanity, so compromised by fatigue that he won't be the best basketball player in the world anymore.

And here we'll allow Magness the final word in our quest for clarity on a subject that will forever defy it:

The NBA, and most professional sports, consists of attempting to go all out and hang on for dear life. It's hoping and praying that you have enough juice to make it to the finish line without hitting the wall. ... But everyone has a breaking point.