A single run more than 10% longer than the longest run of the previous 30 days raised the rate of overuse running injury (HRR 1.52-2.28 by size of spike) in 5205 adult runners followed for 18 months with Garmin data; week-to-week change showed no relation
5205 adult runners recorded 588 071 sessions on Garmin devices over 18 months; 1820 (35%) reported an overuse running injury. Exposures were the distance of a single session relative to the longest run of the past 30 days, the acute:chronic workload ratio, and the week-to-week ratio, each categorised as up to 10% increase (reference), small (>10-30%), moderate (>30-100%) or large (>100%) spike.
Participants
n=5205 adult runners, mean age 45.8 years (SD 10.4), 22% female.
Protocol
18-month prospective cohort, Garmin data, self-reported overuse injury; multistate Cox regression with adjusted hazard rate ratios.
Key Results
Single-session spikes raised the injury rate: small (>10-30%) HRR 1.64 (95% CI 1.31-2.05), moderate (>30-100%) HRR 1.52 (1.16-2.00), large (>100%) HRR 2.28 (1.50-3.48).
The ACWR showed a negative dose-response relationship; the week-to-week ratio showed none.
Authors' conclusion: injury rate rose when a single session exceeded the longest run of the last 30 days by more than 10%.
Practical Application
Grow the long run by no more than about 10% over the longest run of the past month; a single big jump, not the weekly total, was where injuries clustered. Inference: a long run built up gradually is not itself the risk.
Limitations
Observational; injuries self-reported.
Mostly men (78% by arithmetic from 22% female); recreational runners.
The abstract gives the size bands but not absolute distances.
How this entry was checked and changed
Why this level
large prospective cohort with objective training data; injury self-reported; observational