Hamstring Injuries in Major and Minor League Baseball
Authors: Zachazewski James , Silvers Holly J. , Li Bernard , Snyder-Mackler Lynn , Insler Stephanie , Ahmad Christopher S. , Mandelbaum Bert R. 
Published: July 2016

Objectives: The purpose of this study is to test the efficacy of a hamstring injury prevention program designed to address the high incidence of acute and chronic hamstring injuries and re-injuries that occur in the sport of professional baseball. Methods: This was a prospective cluster cohort study assessing the efficacy of an injury prevention intervention designed to address hamstring injury in rookie and professional baseball players participating in Minor and Major League Baseball (N = 213). Each athlete was asked to participate and consented (Johns Hopkins Internal Review Board, Baltimore, Maryland). Those athletes who agreed to participate completed a questionnaire detailing their hamstring injury history. The hamstring injury prevention program was disseminated to each medical staff (team physician, certified athletic trainer and strength and conditioning coach) and they were instructed on how to implement the program. Weekly individual compliance with the program and injury data was collected. At the end of the season, the data were analyzed for program compliance and hamstring (HS) injury rates (both acute and reoccurrence) compared to the control data in the MLB HITS database. All data were stripped of individual and team identifiers prior to analysis. Results: For the major and minor league intervention study, one Major and Minor League organization served as the intervention (INT) team, which encompassed Rookie League, Fall Ball, Class A, AA, AAA and major league rosters (6 total teams). A total of 213 athletes consented to participate: Minor League: N = 173 players and Majors League: N = 40. Weekly compliance, injury incidence and time loss due to injury was compared to the HITS database (age, skill matched control group). The average weighted utilization of the injury prevention program was 25.30 utilizations for the uninjured group compared to 13.53 in the injured group (p=0.09). In the majors, there were 2 HS injuries in the INT vs. 79 in the CON (IR: .025 INT vs .068 CON, p < 0.05); constituting a 25% reduction in HS injury. In the minors, there were 7 HS injuries in the INT vs. 297 in the CON (IR: .039 INT vs. .065 CON, p < 0.05), constituting a 40% reduction in the minor league HS injuries. There was a significant reduction in time loss due to injury for both the major and minor league INT players compared to the CON. For the Major League INT, there were 9 vs. 25.9 days lost in the CON group, resulting in a 65.3% reduction in time loss (p<0.05). The Minor League INT reported a similar finding: 11.63 vs. 21.3 days lost to injury in the CON group, resulting in a 45.3% reduction in time loss (p<0.05). Conclusion: The reduction in hamstring injury in the major and minor league intervention teams is consistent what researchers have reported with respect to the efficacy and value of utilizing a this intervention program in other sports. The intervention is a time and cost efficient means to reduce hamstring injury incidence and time loss in professional baseball players. This study is continuing in a prospective manner for an additional competitive season.