Assessing the Impact of Increased Pull-Up Requirements on Upper Extremity Musculoskeletal Injuries Among Males in the U.S. Marine Corps: An Interrupted Time Series Analysis.

INTRODUCTION

In 2017, the United States Marine Corps (USMC) increased the pull-up requirements of the Physical Fitness Test (PFT) to improve combat readiness, raising concerns regarding potential increases in upper extremity (UE) musculoskeletal injuries (MSKIs). This study assesses the impact of this policy change on UE MSKI incidence among active-duty male Marines.

MATERIALS AND

METHODS

Linear regressions estimated with ordinary least squares were used to perform interrupted time series analyses of UE MSKI rates among male Marines from the Military Health System Data Repository between 2014 and 2023. Upper extremity MSKI rate trends were evaluated pre- (2014-2016) and post-intervention (2017-2023), stratified by age, race/ethnicity, body mass index (BMI), and rank. Newey-West SEs were used in linear regression analyses to adjust for violations from autocorrelation and heteroskedasticity.

RESULTS

The study population included 231,323 Marines in the pre-intervention period (2014-2016) and 313,537 in the post-intervention period (2017-2023). Cumulative UE MSKI proportions increased (9.0%-9.4%). Pre-policy, UE MSKI rates trended downward (b1 = -5.09, P < .001). Post-policy, this trend significantly reversed (b3 = 5.11, P < .001) but not immediately (b2 = -4.00, P = .431). Subgroup analysis revealed sustained increasing rates among Marines <20 years (b1 + b3 = 0.88, P < .001). Conversely, decreasing rates occurred in Marines with obesity (b1 + b3 = -1.09, P = .006), ages 40-49 (b1 + b3 = -1.21, P = .046), and senior enlisted (b1 + b3 = -1.10, P = .012). Warrant officers experienced a significant decrease in UE MSKI rates (b2 = -34.22, P = .007) as well as subsequent trend stabilization (b3 = 6.23, P < .001).

CONCLUSIONS

The 2017 standards were temporally associated with a plateau in previously declining UE MSKI rates. While no immediate population-level spike occurred, the heterogeneity of subgroup responses highlights specific risks for younger personnel. Future policy modifications should balance fitness objectives with targeted injury prevention strategies to optimize readiness.