The Dose-Response Relationship of an Exercise-Based Injury Prevention Program: A Secondary Analysis of a Randomized Controlled Trial on Athletics (Track-and-Field) Athletes Over a 39-Week Follow-Up.

Despite exercise-based injury prevention programs (EIPPs) being widely researched and used, several randomized controlled trials (RCTs) have failed to show their protective effect on injury risk. This is potentially due to underappreciating the EIPP dose-response relationship, by not controlling the analysis for the injuries sustained during the early EIPP implementation period, before the EIPP becomes efficacious. To determine the dose-response relationship of EIPP by controlling for the effects of injuries sustained before it became efficacious. We conducted a secondary analysis of an RCT analyzing the EIPP efficacy in athletics over a 39-week follow-up on 840 athletes, by including only those with 100% response rate. We controlled the statistical analyses for a range of lengths of early EIPP implementation period by either excluding the athletes with early injuries (i.e., exclusion approach) or adjusting for the early injuries' effects (i.e., inclusion approach). We estimated the EIPP's dose-response relationship by measuring the EIPP's effect at each length of the controlled period. When we considered no early controlled period, the EIPP showed no effect (OR = 0.85 [95% CI: 0.67-1.09]; p = 0.209). However, both exclusion and inclusion approaches showed that the EIPP effect increased significantly after 5-6 weeks of controlled period. This relationship plateaued at 7-12 weeks of controlled period, peaking at 10 weeks with the exclusion approach (OR = 0.28 [95% CI: 0.16-0.48]; p < 0.001), and 7 weeks with the inclusion approach (OR = 0.37 [95% CI: 0.25-0.55]; p < 0.001). Acknowledging the dose-response relationship of EIPPs could help researchers to design and analyze RCTs and practitioners to plan EIPP implementation timely. Trial Registration: ClinicalTrials.gov Identifier: NCT03307434.