Single-session distance spikes, not a flat weekly percentage, are what large cohort data actually links to running injury risk
Interpretation
A 5205-runner cohort study found hazard ratios of 1.64/1.52/2.28 for single-session distance spikes of >10-30%/>30-100%/>100% above an individual's own recent 30-day longest run — a much more specific and individualized signal than the commonly repeated '10% rule.' Impellizzeri et al.'s methodological critique explains why ratio-based load metrics (the family the 10% rule belongs to) are statistically fragile in the first place.
Practical implication
Flag single-session distance spikes relative to an athlete's own recent longest run, not a flat percentage of weekly mileage, when building injury-risk guardrails into training-plan logic.
Sources
2 sources, independently verified.
BJSM 59(17):1203-1210. 35% injury rate over the cohort; hazard rate ratios of 1.64 / 1.52 / 2.28 for single-session distance spikes of >10-30% / >30-100% / >100% above an individual's recent 30-day longest run — a single-session spike metric, not the commonly cited flat 10%-per-week rule.
IJSPP 15(6):907-913. Lays out the methodological pitfalls (mathematical coupling, ratio instability, arbitrary thresholds) in acute:chronic workload ratio metrics — the statistical family that simple percentage-increase 'rules' belong to.