Methodology
How a plan is built.
There is no black box. A plan comes from fixed rules, so the same inputs always produce the same plan. Here they are.
1. Fitness becomes a VDOT
Jack Daniels and Jimmy Gilbert's VDOT turns a race result into one number. From a recent race we compute the oxygen cost of the speed you ran and divide by the fraction of your capacity you could hold for that long. A longest-run result is treated as an easy effort. If you give only a level, we assume beginner, intermediate or advanced. VDOT is limited to the range 25 to 85. Try it in the VDOT calculator.
2. VDOT becomes five paces
Each zone is a range of intensity, as a fraction of VDOT.
| Zone | Intensity | Used for |
|---|---|---|
| Easy | 66–74% | Most of your running; conversational |
| Marathon | 80–86% | Long-run finishes and race-pace practice |
| Threshold | 86–90% | Comfortably hard; tempo and cruise intervals |
| Interval | 96–100% | Hard repeats of 3–5 minutes |
| Repetition | 103–108% | Short fast reps with full recovery |
3. Periodization, Pfitzinger-style
Plans run from 6 to 20 weeks, counted back from race day. Weekly distance climbs in steps, with a lighter week every fourth week, then peaks and tapers. The marathon tapers for three weeks when the plan is 16 weeks or longer, and two weeks otherwise. The half marathon, 10K and 5K taper for two. The phases are base, build, peak and taper.
One long run every week, built from a share of the weekly distance, with a cap (32 km for the marathon). In the build and peak phases the long run finishes at marathon pace. Quality sessions are threshold or interval work, scaled to the distance you are training for. Race week has no long run and no hard session: a short shakeout, one run with a few short efforts at race pace, and the race.
4. The adaptive rules (in the app)
- Missed workouts. Miss two or more in a week, or tap "Make easier", and the next open week comes down 15 percent, long run included. The app never adds distance to catch up.
- Two bad weeks. Two weeks in a row with two or more missed workouts and the app suggests restarting from the previous week. You choose to restart, continue or make it easier.
- Getting fitter. If you run your easy runs faster than your easy zone on at least two runs in each of two weeks in a row, VDOT goes up by one (at most two in four weeks) and the paces for the open weeks update.
- Injury mode. The next three weeks become return weeks: walk-run sessions, no quality work, and a long run of no more than 8 km. Switch it off and the plan resumes.
- Moving a workout. A moved workout keeps its content, and the week's total is whatever remains in it.
What this is not
It is rule-based, with no chatbot and no learning from other people's data. It is general training guidance and not medical advice. See our terms.
Sources: Daniels' Running Formula (VDOT and training intensities); Pfitzinger and Douglas, Advanced Marathoning (periodization ideas); Riegel (race-time prediction, exponent 1.06). MarathonPlan is not affiliated with these authors.