Even a terrific fastball hitter like Buster Posey has a speed limit. Not long ago, the San Francisco Giants’ catcher quizzed a few older ballplayers about the recent invasion of flame-throwing heat monsters.

“I’ll ask them. ‘Is it just me?’ I mean, I’m about ready to move the mound back a little bit,” Posey cracked.

“You have middle-relief guys coming in throwing 100 mph. And I’m like, ‘Wait, I thought 100 mph was supposed to be one or two guys across the league.’ ”

It’s not just you, Buster. Triple-digit radar gun readings, once the sole provenance of legends like Nolan Ryan, now make for a crowded expressway.

A record 31 big league pitchers touched 100 mph on the radar gun last season, according to PITCHf/x data, and two pitchers – Aroldis Chapman and Mauricio Cabrera – averaged at least 100 mph for the season.

There’s more heat in the forecast. Baseball America documented another 71 prospects clocked at 100 mph in the minor leagues last year.

The fastball fixation is nothing new. You can fairly trace pitching history through baseball’s rapidly spinning seams, from Walter Johnson to Bob Feller to Bob Gibson to Nolan Ryan to Aroldis Chapman.

But it’s becoming increasingly clear that baseball’s best arms are cruising at dangerous speeds. Pitchers are getting injured at record rates, and a recent wave of studies demonstrates a relationship between increased velocity and increased risk in Tommy John surgeries.

There are apparently only so many Newton-meters of torque a human elbow can take.

“We’re seeing so many young kids coming up throwing 95-98. They throw as hard as they can for a full season,” Oakland A’s catcher Stephen Vogt said, “and they come back the next season and their arm is gone.

“I think it’s become the mentality of a lot of organizations: ‘Well, let’s just use this guy until he can’t pitch anymore and next in line.’ I’m not a big fan of that.”

Velocity has gone up or held steady in 14 of the past 15 seasons. In the bullpen, especially, it’s as if everyone suddenly comes equipped with a Goose Gossage fastball. It’s not just Goose anymore, it’s geese: The top 20 relievers last year averaged 96.72 with their heaters, according to numbers collected from fangraphs.com.

Better training, more sophisticated throwing programs and advances in medicine have paved the way for this generation of young, hard throwers. But there’s no way to strengthen an elbow ligament, leaving the UCL to bear the brunt of this unprecedented fastball force.

Stan Conte, the former Giants and Dodgers trainer, last year was the first to report that while shoulder injuries are on the decline in major league baseball, the number of elbow injuries continues to rise.

The trend of mega-velocity has been described as baseball’s Faustian bargain: Throwing hard will get you drafted and could make you a star – and then, almost certainly, it will destroy you.

“Our bodies are not designed to withstand that kind of velocity,” Vogt said. “If you can, you’re a freak.”

THROWING FOR SHOW

In 2008, the PITCHf/x system was installed in all 30 ballparks, creating a generation of rubberneckers who swivel to see the MPH on the scoreboard.

“I feel like that’s the main thing that you look for,” A’s right-hander Jharel Cotton said. “If I throw a pitch and I think it’s hard, I’ll look back and say, ‘OK, that’s pretty cool.’ ”

Chapman, of course, is the reigning king of pop.

According to MLB’s Statcast, the left-hander threw the 30 fastest pitches in the majors in 2016, with the swiftest coming on a 105.1 mph fastball on June 18 against Baltimore.

Pitchers are so reliant on stadium readings that opponents have been known to pull a fast one (at least before MLB cracked down on the antics). Kevin Towers, the former Padres general manager, said his team used to intentionally dial the gun down whenever Brad Penny of the Los Angeles Dodgers took the mound in San Diego.

“He liked velocity. He’d stare at the board,” Towers told the Arizona Republic in 2011. “He was throwing 95-96, but we’d have it at 91 and he’d get (ticked) off and throw harder and harder, and start elevating.”

Long before that, back when radar guns at the stadium were a mere novelty, teammates used to mess with A’s right-hander Steve McCatty.

“They had me looking up at the board in Texas one day and I said, ‘I’m throwing 101,’ ” McCatty told Bleacher Report. “Then it was 103. And then I realized it was the temperature.”

That was a good gag for the old days, but those numbers no longer seem so laughable.

In 2010, the average fastball for a qualified major league starter was 90.5. Last year it was up to 91.76.

Why are pitchers throwing harder than ever?

“Because they’re trying to,” deadpanned one injury expert.

The expert wasn’t being sarcastic. It was a perfect four-word summation for a world gone mad for mph. From the youth leagues on up, the gun is god.

Players recognize from an early age that velocity gets you the college scholarship. Kids know a good heater gets you drafted. Vogt sees the cult of the radar gun every time he agrees to catch a high school kid during the offseason.

“They’ll come out and they’re throwing as hard as they can. And I’m diving for the ball,” Vogt said, shaking his head. “I’ll ask, ‘Hey, what are you working on?’ And they’ll say, ‘I’m just trying to throw hard.’ ”

When young pitchers go to a showcase where scouts are watching, they aren’t trying to paint the outside corner. They’re trying to light up the gun.

It should be no surprise, then, the biggest rise in Tommy John surgeries is among 15- to 19-year-olds. The surgery rate for that age range rose 9.1 percent per year between 2007-11 according to one study.

VELOCITY AT A PRICE

Mike Reinold, a former Boston Red Sox head trainer and current Chicago Cubs consultant, is among those urging for cooler heads when it comes to high heat.

Reinold, the founder of Champion Physical Therapy and Performance in Boston, has emerged as one of the leading voices when it comes to the care and feeding of young arms.

He’s open to new training methods but said the problem is that “the internet has gone crazy.” Reinold said young pitchers are seeing eye-popping videos online and rushing to put their blind faith into programs yet to be backed up by data.

To help science catch up, Reinold was part of a study on the effects of using weighted baseballs to increase velocity. The findings remain preliminary, but appear to fall in line with baseball’s larger trend.

The good: 86 percent of Reinold’s participants added 4 percent to their mph readings.

The bad: 27 percent of the participants wound up injured. And Reinold said that was with an extremely conservative approach over a mere six-week program.

What really raised red flags for Reinold during the study was that they found using weighted balls yielded almost immediate physiological changes. Participants developed more external rotation in their shoulder, which is good for velocity but also correlates with higher injury risk. These arms were being pushed past their limit.

Troubled by the landscape, Reinold not long ago wrote a cautionary tale on his blog: “We have enough evidence to know that weighted ball training helps to increase pitching velocity. We’ve known this for decades. But at what cost?

“I hear this comment all the time from injured baseball players: ‘I started a weighted ball training program this winter, gained 3-5 mph on my fastball, and then hurt my arm for the first time during the season.’ I can’t tell you how common that is.”

ADDING MOVEMENT TO A PITCH

As pitchers reach for anything to give their fastballs a boost, hitters are forced to keep pace. At what point does a pitcher throw so hard it’s unhittable?

Is it 108 mph? 110? 115?

None of the above, Giants outfielder Hunter Pence said.

“No matter how hard you throw, it’s hittable,” Pence said. “There’s no one with a 0.00 ERA. There are some tremendous pitchers out there, but there are also good hitters. It’s just the nature of competing against the best.”

The 2016 documentary “Fastball” asked physicists to explain the difference between a good heater and a great one. A 90 mph fastball takes 450 milliseconds to reach home plate. A 100 mph fastball takes 396 milliseconds.

But, impossibly, hitters still manage to get the timing just right. Even the mighty Chapman can be had. A’s outfielder Rajai Davis, who played for Cleveland last season, blasted a 97.1 mph four-seamer from Chapman into the seats during Game 7 of the World Series last year.

Less remembered, except in the A’s clubhouse, is what Vogt did against Chapman on Aug. 7. Vogt fell behind 0-and-2 in the count.

“Everyone in the world knows that you’re going to strike out,” Vogt recalled this spring. “In a situation like that, you just kind of hope that he throws it in the zone. Because at 104, there’s no way to determine if it’s a ball or a strike. And that’s the honest truth.”

So Vogt banked on getting a fastball and decided if it was anywhere near the strike zone, he’d take a rip. The result was a single against a 103.9 mph rocket. At the time it was the fastest recorded pitch ever to be returned for a base hit. (Francisco Cervelli got Chapman at 104.2 a few weeks later.)

What if Chapman had thrown Vogt a slider?

“Had it been a slider,” he said, “I would have screwed myself into the ground and laughed my way back to the dugout.”

Such is life for hitters in this era. Batters are so accustomed to gearing up for the heat that so-called “soft throwers” – merely in the low 90s – now find it easier to exploit the art of pitching.

“They’re always looking to hit the fastball, and I personally think that’s helped my game,” Giants reliever George Kontos said. “A little bit of movement – whether it’s a sink or a cut or a good change-up – will have guys mis-hitting the ball just off the sweet spot.”

A’s reliever Sean Doolittle, who has spent his career in the 95 mph range, is finding new ways to approach hitters as he works his way back from injuries.

“The hitters have adapted. It’s just weird how it works,” Doolittle said. “It’s not about just throwing hard anymore. It’s more, ‘Can you cut it? Can you sink it? Can you have some deception in your delivery to make it seem harder than it is?’ ”

THROW UNTIL YOU CAN’T

There’s a common phrase in major league clubhouses these days: “Go until you blow.” The mentality is to throw as hard as you can for as long as you can because there is always more gas out in the bullpen.

Pitchers used to pace themselves, or at least vary the speeds of their fastballs. Tug McGraw called his hardest pitch a “John Jameson” fastball – that was a straight, hard one named after the Irish whiskey. But McGraw also threw a Peggy Lee, a slower one in honor of her song, “Is That All There Is?”

These days? Every pitch is a power ballad. Hunter Strickland was the hardest-throwing Giants pitcher last season. His four-seam fastball averaged 97.7 mph.

“I’ve learned very quickly that you can’t just throw a ball by somebody. But at the same time you can’t shy away from who you are,” Strickland said this spring. “So I still stick with my strengths, no matter what.”

Nolan Ryan pitched for 27 seasons, keeping the fastball fire burning until his elbow gave out at age 46. But for mere mortals, the risk of injury is real with every triple-digit pitch. The motto for this hard-throwing generation ought to be live fast, die young, leave a beautiful radar gun reading.

“The time of relief pitchers lasting 15-20 years is going away,” Vogt said. “It’s getting younger and younger. And it’s, ‘Come in and throw as hard as you can.’ Because if you can’t throw it 95, you’re not going to make it.”