REF-602 · Jayanthi, LaBella, Fischer, Pasulka & Dugas, 2015 · The American Journal of Sports Medicine, · Paper · PubMed
Early sport specialization independently raises injury and serious-overuse-injury risk in young athletes
Beyond age and weekly hours; two simple load flags (hours/week > age; organized:free play > 2:1) roughly double the odds
Participants
n=1190 athletes aged 7–18 with usable data (1214 enrolled; 50.7% male): 822 injured (846 unique injuries) vs 368 uninjured controls.
Protocol
Case-control study (Level of evidence 3): injured athletes aged 7 to 18 years recruited from 2 hospital-based sports medicine clinics, compared with healthy controls from affiliated primary care clinics undergoing sports physicals (2010-2013) (from the abstract).
Surveys reported hours per week in organized sports, physical education class and free play, the degree of sports specialization and Tanner stage; heights and weights were measured.
Injury details came from athlete surveys and electronic medical records.
Key Findings
Injured athletes were older (14.1 ± 2.1 vs 12.9 ± 2.6 y) and did more total physical activity (19.6 ± 9.2 vs 17.6 ± 8.9 h/wk) and more organized sport (11.2 ± 2.6 vs 9.1 ± 6.3 h/wk).
After adjusting for age and weekly sport hours, sports-specialized training was an independent risk for injury (OR 1.27, 95% CI 1.07–1.52) and for serious overuse injury (OR 1.36, 95% CI 1.08–1.72).
Two load markers for serious overuse injury: weekly organized-sport hours > age in years → OR 2.07 (1.40–3.05); organized-sport : free-play ratio > 2:1 h/wk → OR 1.87 (1.26–2.76).
Growth rate was NOT related to injury (4.8 cm/y in both groups).
Practical Application
In 1190 young athletes, single-sport specialization independently raised the odds of injury (OR 1.27) and serious overuse injury (OR 1.36) after adjusting for age and hours, and training more hours per week than one's age in years roughly doubled serious-overuse odds (OR 2.07) — so keep multi-sport sampling through childhood and cap weekly organized hours at the child's age.
Watch two red-flags: (1) weekly organized hours > age in years; (2) organized sport more than twice free-play hours — dial back; build rest from the primary sport.
Growth spurts themselves did not predict injury here; the load pattern did.
Youth-specific — not an argument against specificity in the adult reader's own periodized program.
Limitations
Case-control (association, not causation); referral/self-report bias (clinic-recruited cases, survey-reported hours and specialization); Level of evidence 3 per the authors.
How this entry was checked and changed
Why this level
regraded 2026-09-27 from B: large observational case-control, n=1190 analysed
Content correction 2026-09-27
Added the abstract's numbers: n=1190 (822 injured / 368 controls), ORs 1.27 / 1.36 for specialization, OR 2.07 for hours > age, OR 1.87 for organized:free play > 2:1, growth rate 4.8 cm/y not related to injury.
"burnout" removed from findings and tags: not measured in this study.
Level B -> B+ (large observational study, n=1190); Tier "N/A" -> Tier 1-2.
2026-09-28: added Protocol from the abstract (Europe PMC PMID 25646361).