How to use the Long Run Planner
Long Run Planner suggests how far your next long run can safely be, based on the longest run you've done recently.
How to use it
- Fetch your recent runs from Intervals.icu, or enter your longest recent run by hand (add an average pace to estimate duration).
- Move the progression slider (−25% to +100%) to see how the planned increase compares with the injury-risk zones.
- Copy the generated workout, or push it straight to your Intervals.icu calendar.
How it works
The risk zones come from a 2025 study that followed 5,205 runners: Frandsen et al., British Journal of Sports Medicine. It compared the length of each run with the longest run in the previous 30 days. Compared with runs up to 10% longer, the overuse-injury rate was:
| Run length vs longest in last 30 days | Injury rate |
|---|---|
| Up to 10% longer | Baseline |
| 10–30% longer | 1.64× (64% higher) |
| 30–100% longer | 1.52× (52% higher) |
| More than 100% longer (over double) | 2.28× (128% higher) |
In the same study, spikes in the popular acute:chronic workload ratio and week-to-week mileage changes did not predict injury in this way. The length of a single run relative to your recent longest did. That's why the planner looks at your single longest run and uses a 30-day reference period by default.
Related
References
- Frandsen JSB, et al. How much running is too much? Identifying high-risk running sessions in a 5200-person cohort study. Br J Sports Med. 2025. PMC
RunTK's tools are for planning and education. They aren't medical advice, and the right numbers for you depend on your health, experience and goals.
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