Running distances exceeding 10% of the longest session in the prior 30 days increased injury rates in recreational runners, according to a prospective cohort study published in the British Journal of Sports Medicine.
Among 5,205 runners (mean age = 46 years; 22% female) followed for 18 months, 35% (n = 1,820) sustained running-related injuries during 588,071 recorded sessions. Investigators used Garmin GPS devices to track changes in running distances and calculate training-related exposures using three methods: session-specific distance relative to the longest run in the past 30 days, the acute-to-chronic workload ratio (ACWR), and week-to-week ratio.
Multistate Cox regression analysis revealed increased injury rates for all categories of single-session distance spikes compared with runners who maintained distances within 10% of their longest recent run. Small spikes (greater than 10% to 30% increase) and moderate spikes (greater than 30% to 100%) had heightened risks of injury; however, large spikes (greater than 100%) were significantly more likely to result in injury compared with controls.
For the ACWR, the analysis demonstrated an inverse relationship. Small spikes showed no statistically significant association with injury, whereas moderate spikes and large spikes showed decreases in running-related injury. The week-to-week ratio similarly showed no statistically significant associations across all spike categories.
The study population comprised predominantly European and North American runners with a median running experience of 9.5 years. Mean body mass index was 24.2 kg/m². Median time at risk was 80 running sessions. Among the 1,820 injuries reported, 72% (n = 1,311) of them were classified as overuse injuries and 28% (n = 509) of them as traumatic injuries.
Dose-response visualization showed injury hazard ratios increased progressively as single-session distance exceeded the longest recent run. The relationship between ACWR and injury rate showed the opposite pattern, with higher ratios associated with lower injury rates.
Study limitations included reliance on self-reported injury classification, inability to provide subgroup-specific recommendations because of limited injury numbers, and predominance of male runners (78%) limiting generalizability. The observational design also precluded definitive causal claims about injury prevention.
"A significant increase in the rate of running‐related overuse injury was observed when the distance of a single running session exceeded 10% of the longest run undertaken in the previous 30 days," wrote lead study author Jesper Schuster Brandt Frandsen, MSc, of the Big Data Centre for Environment and Health at Aarhus University, and colleagues.
Full disclosures can be found in the study. The authors reported no competing interests.
