In the top of the third inning of a March 25 Spring Training game against the Braves in Lake Buena Vista, Fla., Mets center fielder Juan Lagares stepped into the batter's box against knuckleballer R.A. Dickey. A few pitches into the at-bat, he fouled a ball off awkwardly and ran down the line as he watched it roll out of play. Lagares grounded out on the next pitch, then he promptly left the game with pain in his left side.
In retrospect, Lagares thinks both the stiffness he felt after the two-hour bus ride from Port St. Lucie up to the Orlando area and the adjustment he had to make to Dickey's knuckleball contributed to his oblique strain.
"Those pitches, you see them in the middle. and in the last moment. they go away," Lagares said.
What, exactly, are the oblique muscles? They lie alongside the rectus abdominus muscles -- the ones that make up the "six pack" -- and they are responsible for core control and rotation. The internal oblique sits under the external oblique, and it is the most commonly injured abdominal or core muscle in baseball, because it is the most activated core muscle during hitting and throwing.
According to a new study done by former Dodgers athletic trainer Stan Conte of Conte Injury Analytics. in conjunction with the Hospital for Special Surgery and Major League Baseball and using MLB's Health and Injury Tracking System (HITS) data, there was an uptick in oblique injuries in 2016. Fifty-six percent of oblique injuries are suffered by hitters, 44 percent are suffered by pitchers and 77 percent of all oblique injuries occur on the contralateral -- or lead -- side in both pitchers and hitters. That is, the left side for a right-handed hitter or thrower, and vice versa.
But why the uptick at all? Conte's theory is simple.
"Players are bigger, stronger and faster than ever, and it has led to an increase in velocity and bat speed," he said. "They go together. If a pitcher throws harder, the hitter has to have reciprocal bat speed to catch up. He has to explode more and swing harder."
Today's players strength train year-round to develop explosive power, and the leg and lower extremity strength of the average baseball player has dramatically increased. As that increased force travels up the kinetic chain and through the body into the ball or the bat, the oblique muscles, which are smaller and harder to strengthen, can simply get overloaded.
"If that oblique isn't strong enough to handle the force from the legs, it gives," Conte said.
Former Red Sox trainer Mike Reinold, now of Champion Physical Therapy and Performance in Waltham, Mass., has a related theory. Today's MLB players played many sports growing up, and after years of pounding, often reach the big leagues with some kind of impingement or limited range of motion in their hips. If a pitcher or hitter's hips are tight and less able to rotate, the core has to make up for the lack of mobility.
"To make the math simple, say, when you rotate, half the rotation comes from your hips and the other half comes from your core," Reinold said. "If your hips are tight and only give you 30 percent rotation, your core has to move extra to get up to 100 percent rotation. You overstrain your core because you don't have the hip mobility."
Reinold also thinks Lagares is onto something. While pitching mechanics are generally repeatable, hitters can often be thrown off balance by unexpected movement on a pitch.
"If you react quickly to a breaking ball when you're expecting something else and it causes you to make an awkward swing, you could certainly end up with an oblique strain," Reinold said.
While the 10-day DL is the most common starting point for oblique injuries, Conte's study showed that hitters typically took 27 days to recover, while pitchers took 35. Lagares missed 18 days for the Mets, though more mild strains can certainly be resolved in just a few days. However, those with oblique injuries often see setbacks on the road to recovery.
While players may pass exams on the training table, the speed and power needed to play simply cannot be reproduced in that setting. Rehab is especially difficult with hitters, who have a harder time with partial-effort swings than pitchers do with just playing catch.
"Pitchers can throw lightly, do some long toss, do things that use the same motion as pitching but are less stressful," Reinold said. "But with hitters, hitting causes the injury, we're getting them back to hitting, and trying to swing a bat lightly against live pitching is just a very difficult thing to do. Sometimes the comeback is a little too fast, and we'll find out quickly they're not 100 percent."
Conte is quick to point out that though oblique strains are very specific to baseball, they occur with relatively low incidence when compared to more common baseball injuries, like those to the shoulder and elbow.
"The majority of the time, the oblique muscles work great," Conte said. "And sometimes, they don't."
Lindsay Berra has covered a variety of sports, from baseball and hockey to tennis and the Olympics, since 1999. She joined MLB.com in 2013. This story was not subject to the approval of Major League Baseball or its clubs.