Mets starting pitcher Zack Wheeler delivers against the Washington Nationals...

Mets starting pitcher Zack Wheeler delivers against the Washington Nationals during an MLB baseball game at Citi Field on Saturday, Sept. 13, 2014. Credit: Kathleen Malone-Van Dyke

Hall of Fame executive Branch Rickey called baseball a game of inches. The tip of an outstretched finger can be the difference between safe and out, and games have been won and lost on the hairbreadth between ball four and strike three. And for decades, the fate of hundreds of pitchers -- of entire seasons and even careers -- has been determined by damage to a small stretch of thick, triangle-shaped connective tissue in the elbow.

Matt Harvey was a victim. He underwent Tommy John surgery to repair the torn ligament in his right elbow and had to be shut down for part of the 2013 season and all of 2014. And less than two weeks ago, Mets teammate Zack Wheeler, who came to spring training with that telltale twinge in his right elbow, met the same fate.

The ulnar collateral ligament, or UCL, has entered common parlance for sports fans, but more than 40 years after Dr. Frank Jobe first performed his breakthrough surgery on Tommy John, there are lingering questions over what factors and what motions lend themselves to the stress that leads to tearing or rupture.

Unpopular mechanics

"There's always a natural assumption that if you have bad mechanics, you're more prone to injury," Dr. David Altchek said from his office in the Hospital for Special Surgery in Manhattan. "That's probably the opposite, because good mechanics promote more force, more velocity. I'm not promoting bad mechanics, but if there's any powerful correlation with the injury, it's the power pitchers.''

Altchek, the Mets' team doctor, would know. He's performed almost 1,000 Tommy John surgeries, he said, including the one on Wheeler. In 1994, he helped pioneer a "docking'' technique, considered less traumatic than traditional Tommy John surgery. On its website, the hospital explained that the technique entails splitting the muscles and keeping the ulnar nerve in place as opposed to detaching the muscle and moving the nerve.

Altchek ticked off the risk factors for a pitcher: how hard you throw, how much you throw, average velocity, the type of pitch you throw and the condition of your shoulder. Since the UCL can develop tears over time and the repetition of motion, there can be countless more factors, he said, and information is always emerging. One thing, though, is certain -- there is one part of the pitching motion that is far more traumatic than all others.

He gave an example with a baseball bat. Batters bring their bats back to help provide the force they need to hit the ball. "Why are they doing that?'' he said. "They're building up the potential energy in their forearms, wrists, hands and in the bat itself. The bat is almost bending a little bit, then they release all that energy. It's the same thing with pitching.''

This time, though, it's the arm that's bending. Altchek demonstrated, cocking his arm back, mimicking a pitcher gathering momentum before the arm goes forward.

"They leave their arm behind for a second and it builds up energy. Then they release it,'' he said. "It's that early acceleration where the load peaks.''

And, said Dr. Glenn Fleisig, research director for the American Sports Medicine Institute, it's at this point of extreme stress -- the moment when the arm is back and the palm is up -- when the UCL comes into play. Its job is to stabilize the elbow and, by extension, the arm, he said.

While the shoulder takes the brunt of the stress during other parts of the pitching process, in this phase, the elbow is responsible for stopping backward progress and redirecting the arm forward so it can continue on to the next two phases of arm deceleration (the point before release) and follow-through.

"All these Tommy John injuries happen when the arm is back,'' Fleisig said. "It's always the most stressful time.''

It's known as "varus torque,'' and thanks to the advent of biomechanics -- literally, the use of machines and technology to study biology -- the data available on this torque, or elbow stress, are getting more and more refined.

Pitching sleeve

"Put out your arm,'' Ben Hansen said. "Now when I push against your wrist'' -- he pushed lightly against the outstretched arm, moving it away from the body -- "Push back . . . you feel that in your elbow? That's the UCL.''

Hansen, the vice president and chief technology officer at Motus Global, is on the cutting edge of sports biomechanics. Four years ago, his Massapequa-based company began developing a pitching sleeve that measures a host of things -- from workload to arm speed to arm slot to, yes, varus torque.

Pitchers usually have to wear multiple sensors all over their bodies, but this sleeve -- with a sensor about the size and shape of a blue packing peanut -- is simple enough for everyday use. Nine major league clubs used the sleeve in their fall instructional leagues, Hansen said, and, after winter meetings, that total ballooned to 25, including the Mets and Yankees.

The sensor works with a cellphone so a pitcher can see how he stacked up and even how much stress he put on his elbow.

This means graphs, this means numbers, this means an app named mThrow that changes colors to tell you when you've overworked your arm.

Hansen pulled up his laptop to show a video of a major league pitcher. The pitcher was still doing it old-school, with sensors all over his body. The numbers popping up were consistent with the ones they've achieved with the sleeve, he said.

Specifically, this pitcher, throwing a fastball, was exercising a torque of "87 Newton metres'' on his elbow. For comparison, Motus Global's data stated that the average range for a professional pitcher is between 69 and 106.

What's interesting is the chart that keeps popping up -- both with Motus and with the American Sports Medicine Institute (Fleisig is a board member with Motus and Altchek is a medical adviser). All data, even from studies dating to the 1980s, show the same severe bell curve when it comes to the pitching motion.

There is very little stress put on the elbow in the first two phases, as defined by the ASMI as windup and stride. Then the huge spike happens: From cocking to arm acceleration, the sample graph provided by the institute shows a peak varus torque of more than 89 Nm.

'Million-dollar question'

Added stress can come from multiple sources., an MLB/ USA Baseball initiative that promotes safe pitching practices (Andrews and Fleisig are on the advisory committee), says there is no conclusive evidence whether the height of the mound leads to tears.

That said, both Altchek and Michael "Mickey'' Levinson, a physical therapist at the Hospital for Special Surgery who has treated and overseen hundreds of recovering pitchers (many professional), believe it leads to extra stress.

"Unfortunately, mechanics that allow them to throw the hardest also probably put the most torque on the ligament,'' Levinson said. "Combine that with throwing down a hill [the mound] -- I don't care what the research says out there -- that has to increase the amount of stress on the inside of the elbow.''

So if good mechanics can lead to UCL tears, and throwing fast can lead to UCL tears, and even the mound a pitcher throws from can lead to UCL tears, what's an athlete to do?

"That's the million-dollar question,'' Levinson said.

The truth, Fleisig said, is really bad mechanics can still lead you down the Tommy John path. "When you're throwing, you're not just throwing with your elbow, you're throwing with your whole body,'' he said. "If you do too much of this or too much of that, it's too much stress . . . It's still frustrating that there are so many injuries. I don't have any false pretense that we're going to find some mechanics that are going to make it no injuries.''

Fleisig said the shoulder, core, hips and legs have a big part in the pitching process. In short, if you're the sort of pitcher who practices bad mechanics and doesn't have all these moving parts in sync, you still can tear a UCL.

Even so, every person Newsday interviewed for this article agreed: Velocity and workload are primary factors. Thus, hypothetically, Levinson said, the key to avoiding injury is to work within those confines.

"A lot of these things are hypothetical,'' he said. "We look at the different part of the kinetic chain . . . and maybe there are certain flexibility deficits . . . [like] loss of internal rotation of the shoulder, which can predispose them to putting more stress around the elbow.''

So strengthening the muscles around the shoulder or scapula is an option, he said, as is working on flexibility, "which, theoretically, helps protect the inside of the elbow.''

But as with most things in this extremely faceted nook of sports medicine, a lot of things still are being explored.

"Through sports medicine, pitchers are bigger and stronger,'' Fleisig said. "But the UCL is a ligament [and it] makes your ligaments and tendons a little stronger, but it makes your muscles much stronger. Conditioning is good, and good mechanics is good, but we've created a situation where people can pitch very hard.''

Not only that, but they're pitching very hard at a very young age, incorporating injury-causing sliders as young teens and even pitching year-round -- something, Fleisig said, that is a relatively new phenomenon.

In fact, a chart provided by ASMI that measured youth Tommy John surgery at Andrews Sports Medicine in Alabama noted that, from zero surgeries in 1994, the percentage of reconstructions performed on youth and high school pitchers jumped to 26 percent in 2003 and to 32 percent in 2008. The graph stops at 2011. said numbers from that facility indicated that surgery numbers have almost doubled since 2000.

"Now with specialization, kids . . . show up as a pro and they already have damage in their arm,'' Fleisig said. "They would have been better off, in most cases, playing multiple sports and being athletic.''

Additionally, studies published in the American Journal of Sports Medicine, in addition to anecdotes from Altchek and Levinson, say the idea that pitchers come back stronger from Tommy John surgery is a myth. If they do seem to pitch better, Levinson said, it's because they're more aware and better conditioned and, perhaps most important, not in pain. And not everyone comes back.

"The younger players especially become much more educated on how to take care of themselves,'' Levinson said. "They're all so talented . . . but a lot do no strength and conditioning and rely on that talent . . . Then you rehab muscles around the shoulder, and work on the flexibility that they've never worked at, and you work with the kinetic chain -- legs, hips, core -- and you take away their pain. The elbow just goes for the ride.''

And if the emerging science is any indication, what a ride it is.