Why plan weekly mileage changes?#
Large changes in volume can feel manageable aerobically while still adding unfamiliar musculoskeletal load. A gradual template gives you time to notice how the added distance affects fatigue, soreness, and training consistency.
The 10% Rule is a popular coaching heuristic, not a universal safety threshold. Some runners need smaller changes, while experienced runners may use a different periodized plan.
Our calculator turns a current baseline and target mileage into a step-by-step template with optional Deload (Recovery) Weeks. It is not an individualized coaching or injury-prevention guarantee.
The anatomy of the generated template#
A training plan does not need to rise every week. Optional recovery weeks create room to reduce accumulated fatigue:
- Baseline and Build Weeks: Week 1 is your current mileage. Subsequent build weeks increase from the previous build week by 10% under this calculator’s default settings.
- Recovery Week: With recovery weeks enabled, every 4th week reduces the preceding build week’s volume by 20%.
- Build Baseline: After a recovery week, the next increase is calculated from the previous build week, not the reduced recovery week.
Running Mileage Increase Example: From 30 to 40 km per Week#
Enter 30 km as your current weekly distance and 40 km as your target, with recovery weeks enabled. The calculator’s default 10% build rate produces:
| Week | Weekly distance | Purpose |
|---|---|---|
| 1 | 30.00 km | Current baseline |
| 2 | 33.00 km | Build: +10% |
| 3 | 36.30 km | Build: +10% |
| 4 | 29.04 km | Recovery: -20% from week 3 |
| 5 | 39.93 km | Build: +10% from week 3 |
| 6 | 40.00 km | Reach the target |
Notice the rebound: week 5 is 37.5% higher than the reduced week 4, although only 10% above the preceding build week. This planner does not cap every adjacent week’s increase at 10%. Review that transition rather than treating the generated schedule as mandatory.
Adjust the template around intensity and recovery#
Use a recent, repeatable training week as your baseline, not an unusually high week or a pre-injury peak. Added distance, faster sessions, hills and an unusually long run can all increase workload. Avoid assuming that a modest mileage increase offsets a simultaneous increase in intensity.
If fatigue or soreness is persisting, hold or reduce the planned distance and reassess rather than chasing the target date. After illness or injury, use a return-to-running plan appropriate to your situation instead of automatically resuming the old baseline.
How does this relate to ACWR?#
The Acute-to-Chronic Workload Ratio (ACWR) compares recent load with a longer-term baseline. It answers a different question from a mileage progression template: a 10% build rate describes the planned distance change, while ACWR describes recent load relative to your history.
This calculator does not calculate ACWR or account for your heart rate, intensity or recovery. Neither a 10% increase nor an ACWR value guarantees that a week is safe; use these as context alongside training history and how you are recovering.
Frequently Asked Questions#
Q: Can I increase my mileage by more than 10% if I feel good?
A: Feeling good is useful information, but it does not make 10% a safety boundary. Consider training history, intensity, terrain, recovery, and any persistent discomfort before adding more volume.
Q: What should I do during a Deload (Recovery) Week?
A: The calculator uses a 20% reduction by default. Adjust the amount and frequency around your existing plan rather than treating one percentage or heart-rate zone as mandatory.
Q: How does Apex Run help me review training changes?
A: Apex Run compares recent training load with your longer-term Apple Health history and surfaces changes worth reviewing. These signals do not diagnose or prevent overtraining.