RunTK: Long Run Planner

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API Key

Athlete ID

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Days to fetch

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Run Activities — Last 30 Days

Reference period (days)

Your Longest Run

Progression Target

Distance change from longest run 10%

-25% 0% 25% 50% 75% 100%

Suggested Next Long Run

Injury Risk Zones from study (n=5,205)

Source: Frandsen et al. (2025) "How much running is too much?" Br J Sports Med. PMC12421110

Key Takeaways

The 10% rule applies per-session, not per-week. Compare each long run to your longest run in the past 30 days (risk window) — not your weekly mileage.

Weekly load ratios (ACWR) showed no association with injury risk in this 5,200-runner study. Focus on single-session spikes instead.

35% of 5,205 runners sustained an injury over 588,071 sessions. Keeping your progression ≤10% per session is the evidence-based safe zone.