Unilateral rotation in baseball fielder causes low back pain contralateral to the hitting side.

Low back pain (LBP) often occurs in baseball players;however, the characteristics of the location of their LBP with respect to their throwing and hitting sides have not been clarified. In order to clarify the left-right asymmetry of LBP that occurs in baseball players, we surveyed 247 university baseball players using an LBP questionnaire. The main investigational items were:throwing and hitting side, position at the time of LBP experience, and LBP location. Based upon the indication of their throwing and hitting side, subjects were classified into unilateral rotational (UR) or bilateral rotational (BR) types. Subjects were also classified into categories of LBP location as described by ipsilateral or contralateral to dominant side of throwing or hitting. Chi-square test or Fisher exact test were used to compare LBP location side by rotational type (UR/BR) in all subjects and by position (pitcher/fielder). We found that among fielders, LBP occurring contralateral to the hitting side in UR was significantly more frequent than that in BR. We conclude that LBP occurred in baseball fielders with a left-right asymmetry, which suggests that high frequency unilateral rotation causes the lumbar region contralateral to the dominant hitting side to be subject to a high load. J. Med. Invest. 65:56-59, February, 2018.