"Lat's all, folks." That was the punchline in the New York Post on May 1, the day after Mets ace Noah Syndergaard walked off the mound at Nationals Park, just 1 1/3 innings and 38 pitches into his fifth start of this still-young 2017 season. An MRI -- which Syndergaard had declined to undergo days prior when he was scratched from his scheduled start with biceps soreness -- confirmed a strain of his right latissimus dorsi. And while that may be all for Syndergaard for now, there is plenty more to say about this tricky-to-treat, rather uncommon baseball injury.
For starters, what is it? The latissimus dorsi is the direct translation of its Latin name; it is the broadest muscle of the back. It extends from the iliac crest -- the top of the hip -- to the lower six thoracic vertebrae in the mid back and up to the top of the humerus at the front of the shoulder; the humerus is the long bone in the upper arm that forms the ball of the ball-and-socket shoulder joint.
Most lat strains in pitchers occur at the top end of the muscle near the humerus, which is why they are often difficult to diagnose. They are often initially treated as biceps tendinitis or a rotator cuff issue, because physicians don't always recognize that lat strains can create anterior shoulder soreness due to the attachment at the front of the shoulder.

So what does the lat do in pitching? Quite a lot, especially if you're a pro.
"The best pitchers on the planet use their lats the most," said Eric Cressey of Cressey Performance in Hudson, Mass. "They use big muscles to do big jobs."
Cressey also noted that the lat connects the lower body to the upper body to allow for force transfer that ultimately leads to arm speed and ball velocity.
"The lat is a powerful anterior stabilizer that works eccentrically to prevent the upper arm from flying off the body in the layback phase of the pitching motion when the shoulder is externally rotated," he said. "The lat then helps to aggressively internally rotate the shoulder during the acceleration phase of the delivery."

The lat, quite simply, is an accelerator muscle. And what does Syndergaard do? He accelerates better than the vast majority of pitchers in Major League Baseball. In 2017, Syndergaard is the only starter who averages over 98 mph. And his top fastball velocity of 100.9 mph is only 2.8 mph faster than his 98.1 mph average. So while many pitchers can throw hard occasionally or when they need to, Syndergaard lives at or near his very high max velocity every time he throws a fastball, which is around 60 percent of the time.
Syndergaard is not the only pitcher who throws hard to have dealt with such an injury. Jacob Peavy, Roy Halladay, Kerry Wood, Stephen Strasburg, Joe Kelly, Sonny Gray, Brandon Finnegan, Huston Street and Trevor Rosenthal have all had similar issues. In 2014, Clayton Kershaw spent 41 days on the DL with a teres major strain, which is nearly the same muscle; in 30 percent of people, the two muscles even come together into one tendon. And in '10, Peavy became the first big league pitcher to have a lat surgically repaired when his tore completely off the humerus. Peavy missed a year of baseball with that Grade 3 tear, but returned to become an All-Star in '12.

Syndergaard's strain has been labeled Grade 2, which means it has not torn completely off the bone, and surgery is generally not deemed the best course of action.
"You have to ask, what potential does the lat tendon have to heal versus not heal?" said Dr. Jeff Dugas of the American Sports Medicine Institute in Birmingham, Ala. "If it's torn all the way through and is separated from the bone, it's not going to crawl out and reattach itself. But if it's not completely detached and separated from bone, or separated from itself, it has the potential to heal itself. So do you repair it? Or do you let the patient's biology do it for you? With a Grade 2 tear, it's better to give it a chance."
The fact that the lat is also a core stabilizer used in basically every human activity as well as a respiratory muscle means it never gets a break, which makes resting it enough to allow it to heal a tricky endeavor.
In 2016, a case study done by doctors at the Cleveland Clinic looked at 30 MLB pitchers who had suffered lat or teres major strains. Twenty-nine were treated conservatively and allowed to heal on their own. Only one underwent surgical treatment. The average time required to return to pitching for the non-surgical group was 99.8 days, while the pitcher who had surgery missed 140 days.
Syndergaard, it seems, is looking at that 100-day timeframe.
"Anytime you are dealing with a tendon attachment to a bone, the healing time is six to eight weeks before resisted stress can be applied, which includes throwing," said longtime Dodgers trainer Stan Conte, now of Conte Injury Analytics. "Then, he'll have to start his throwing program from scratch. He'll have to play catch, long toss, increase his endurance, move to the mound, regain his velocity, work in the curveball and the slider, eventually pitch to live hitters, make several rehab starts ... it just takes a long time."
Then, finally, the Mets will again have their ace and be able to say, with all kidding aside, "Lat's all, folks."