Sport Specialization and Risk of Overuse Injuries: A Systematic Review With Meta-analysis

4 studies pooled (of 5 included; 12 screened)

Youth and high-school athletes (pooled across 4 studies)

Systematic review: 12 full texts screened, 5 included, only 4 with poolable data. Specialization graded by the common 3-point self-report scale; outcome = overuse injury. Small evidence base, mostly cross-sectional/retrospective injury-history designs, so the pooled RR inherits recall bias and — critically — incomplete adjustment for training VOLUME, which is braided with specialization by definition.

The most-cited quantitative estimate of the specialization-injury link: highly specialized youth athletes carry roughly 1.8x the overuse-injury risk of low specializers, but only 1.18x that of moderate specializers. That weak dose-response step is what you would expect if the real driver is cumulative training load rather than specialization per se. Only 4 poolable studies — a thin, largely cross-sectional evidence base carrying substantial policy weight.

Injury susceptibility (tendon/bone properties, joint laxity, maturation timing) is substantially heritable; specializers are also self-selected on ability and load tolerance, so specialization status partly reflects the athlete's phenotype.

Directionally consistent with McGuine 2017 prospective (HR 1.85) and Jayanthi 2015/2020; magnitude shrinks toward null in studies that adjust fully for training hours.