Left-handed baseball pitchers may be more susceptible to injury, according to a U.S. study of college pitchers that found differences in the throwing motions of left and right-handed players.
Researchers from the Center for Sport & Motion Analysis at Texas Metroplex Institute for Sports Performance found the mechanics of a left-handed pitcher resulted in more stress on the bone that runs from the shoulder to the elbow called the humerus.
"It's kind of remarkable to me," researcher Dr. Sherry Werner told Reuters Health. "I never would have expected significant differences."
Werner and her colleagues analyzed the pitching motions of 84 collegiate baseball players, looking at the rotation of their pitching and non-pitching arms, the angles of their elbows and shoulders during the pitching motion, and their arm speed.
They then took the 28 left-handed players in the study and matched them up with 28 right-handers of similar age, height, weight, and throwing speed to examine these details of their motions.
"Their range of motion is different to begin with," Werner said, explaining that these mechanical differences could impact the stress on the arm bones. But in terms of significant differences, "the number one thing was torque on the humerus."
This stress is highest, she explained, at the point in the pitching motion where the pitcher has the ball behind him with his arm extended, before the arm accelerates toward the plate. Too much stress on this bone, and it can fracture.
Werner said in the history of Major League Baseball, only four pitchers have had this specific type of injury and all were left-handed.
But there are still questions about whether lefties get injured more than righties in general.
When Werner and her colleagues went back through 10 years of information on who has been on the disabled list in the major leagues, they didn't see any differences but this list is missing a lot of information.
Dr. Glenn Fleisig, research director at the American Sports Medicine Institute in Birmingham, Alabama, who was not involved with the study, said that his research has not shown any differences in the biomechanics of left and right-handed pitchers.
"I don't know why lefties and righties would inherently be physically different," he told Reuters Health. But, he said, "it's certainly worth further investigation."
Werner hopes the current study will spur larger, more in-depth studies of pitching injuries.
"We need to understand the differences and know that if we're looking at a lefty, we're not expecting them to look like a right-hander," she said.