Editor's note: Please welcome John Butterworth to our Fish Stripes! John will be doing weekly injury-related pieces and a little analysis for our site, with my input as a physician placed when needed. Here's his first piece! -MJ
Wei-Yin Chen is a strong addition to the Miami Marlins staff. Not only has he produced solid results with consistent improvement, but he has also been fairly durable.
In three out of his four years in the MLB, he started at least 30 games and pitched over 185 innings. His only trip to the DL occurred in 2013 due to a right oblique strain - he still managed to pitch 137 innings over 23 games that season. Due to his healthy MLB career, I expected Chen to have an excellent pitching delivery with sound mechanics. However, when I took a closer look, that was not the case.
Ideal pitching mechanics effectively transfer energy from the legs, to the torso, to the arm. Timing each movement perfectly is critical to minimize stress on the throwing shoulder/elbow. Research has shown that it is especially important to synchronize a pitcher's trunk/torso rotation with the throwing arm. A 2015 study in the Orthopaedic Journal of Sports Medicine at Medstar Washington Hospital Center found that early trunk rotation, defined as " trunk rotation before the stride foot hit the ground and occurrence of non-vertical arm position at initiation of trunk rotation," increases risk of shoulder and/or elbow injuries in MLB pitchers. Here is an example sketch of early trunk rotation from the 2015 paper: