The PacePlotter method
No black box, no "AI coach": every PacePlotter plan is produced by a deterministic, published algorithm, laid out below.
1. Riegel's formula: your equivalent times
From your reference time, your equivalent times over the other distances are calculated with Peter S. Riegel's formula (engineer and runner; formula published in 1977, then in American Scientist in 1981):
T₂ = T₁ × (D₂ / D₁)1.06
It rests on a robust empirical observation: sustainable pace drops by about 6% when the distance doubles. Its limits are well known: it assumes training adapted to the target distance (a pure 5K runner isn't "worth" their marathon equivalent without marathon training) and loses reliability at the extremes.
2. The derived training paces
Your workout paces are derived from your equivalent race paces, using classic ratios from endurance training:
| Pace | Definition | Calculation |
|---|---|---|
| Intervals | Short repeats (300-1,000 m) | equivalent 5K pace |
| Threshold | Continuous blocks of 8 to 40 min | equivalent 10K pace × 1.04 |
| Marathon pace | Specific segments in the long run | equivalent marathon pace |
| Easy pace | Easy runs and long runs | equivalent marathon pace × 1.18 |
All paces are rounded to 5 s/km. That's the realistic precision of a plan you run by your watch.
3. Plan structure
- Three phases: base (≈40% of the plan), build, taper (1 to 3 weeks depending on the distance).
- A recovery week every 4 weeks: volume reduced by about 25%, quality maintained.
- A progressive long run, capped by distance and by level (for example 26 km for a first-time marathoner, 32 km for an experienced one), peaking at the end of the build phase.
- Progressive quality workouts: longer repeats and extended threshold blocks as the phases advance; for the marathon and the half, race-pace segments built into the long runs.
- A lightened race week: two short sharpeners + the race.
4. The safety rails
PacePlotter refuses to generate a structurally dangerous plan:
- Minimum duration per distance: 6 weeks (5K and 10K), 8 (half), 10 (marathon); 12 for a marathon with a beginner profile.
- Long-run progression capped; never more than 5 workouts per week.
- Absurd reference times rejected (pace outside the 2:30–12:00/km range).
5. What PacePlotter is not
A generated plan replaces neither a coach (who, unlike a plan, adapts to your real fatigue, your injury history, your life) nor medical advice. It assumes you can already run regularly without pain. If you have any doubt about your health, see a doctor — especially for a certificate before a competition. Listen to your body: a pain that lingers is always worth more attention than one more workout.