What does the Race-Week Taper Planner calculate?

Methodology for the Race-Week Taper Planner: Bosquet 2007 meta-analysis, distance-aware depth, and Pfitzinger-style weekly structure.

What inputs does the Race-Week Taper Planner require?

It takes the following inputs: peak volume, peak intensity, taper start weeks before, race distance.

What does the Race-Week Taper Planner return?

It returns: optimalVolumeCutPct, intensityRetentionPct, frequencyReductionPct, raceDistance, taperStartWeeksBefore, weeklyPlan.

Is the Race-Week Taper Planner free to use?

Yes. It runs entirely client-side in your browser with no signup, and is also importable as an ES module engine for AI agents.

What category does the Race-Week Taper Planner belong to?

Planning. See the methodology above for formulas, assumptions, and limitations.

Methodology: Race-Week Taper Planner

Scope

Builds a 1–3 week taper for endurance race preparation. Returns the optimal volume cut, weekly volume targets, longest-run guidance, and intensity-session frequency for each taper week.

Formula

Race-week retention defaults to 40% of peak. The taper start week retains 1 − 0.5 × distance_depth, with linear interpolation between.

Distance-aware final cut depths:

5K: 40% volume cut
10K: 45%
Half marathon: 50%
Marathon: 55%
Ultra: 60%

Frequency reduces ~20%; intensity (paces / power) is held at 90% of peak.

Data sources

Bosquet L, Montpetit J, Arvisais D, Mujika I. Effects of tapering on performance: a meta-analysis. Med Sci Sports Exerc. 2007;39(8):1358-1365. — PMID 17762369. The canonical 41–60% volume reduction over 8–14 days finding.
Pfitzinger P, Latter P. Advanced Marathoning. 3rd ed. Human Kinetics; 2019. — Practical 3-week marathon taper structure (cuts each week of long run by 25-50%).
Mujika I. Tapering for Triathlon Competition. J Hum Sport Exerc. 2011;6(2):264-270. — Multi-distance taper depth guidance.

Assumptions

Peak volume reflects the highest sustained week in the prior 8 weeks, not a single one-off spike.
Intensity sessions during taper preserve race-pace work (Pfitzinger / Daniels approach), not VO2-max intervals.
Race-day fitness gain ≈ 0.5–1.96% (Bosquet 2007 mean) — taper protects rather than builds.

Approximation range

Taper response varies by individual. Some athletes report best results at 2-week tapers, others at 3-week. The model errs toward the 2-week median, which has the strongest evidence base across distances.

Limitations

High-risk tool — over-tapering can leave an athlete flat on race day; under-tapering robs final adaptations.
Doesn't model strength training or cross-training, which often need their own taper.
Doesn't account for "the line" — individual flat-spot risk during taper week is real and not captured.

Reproducibility

Marathon, peak 80 km/wk, 3 quality sessions, 2-week taper: final cut = 55%. Week −2 = 80 × (1 − 0.275) = 58 km. Race week = 80 × 0.4 = 32 km.

Change log

2026-05-08: methodology page first published.

Marathon Pace + Elevation Calculator — Plan race-day pacing.
Sweat-Rate + Electrolyte Marathon Plan — Race-day hydration.
Run Training Paces Calculator — Training paces around the build phase.

Worked example

Computed by the same engine bundle served at /engines/race-week-taper.js. Re-runnable: the values below are the literal output of compute(engineInput).

Input

tool: race_week_taper
peak_volume: 80
peak_intensity: 3
taper_start_weeks_before: 2
race_distance: marathon

Output

optimalVolumeCutPct: 55
raceDistance: marathon
taperStartWeeksBefore: 2
weeklyPlan: [{"weekFromRace":2,"volumeKm":80,"volumeCutPct":0,"intensitySessions":2,"longestRunKm":36,"notes":"Cut weekly long run by ~25%; keep intensity sharp but shorten reps."},{"weekFromRace":1,"volumeKm":32,"volumeCutPct":60,"intensitySessions":2,"longestRunKm":14.4,"notes":"Race week — short shakeout efforts, no new stimulus, prioritize sleep and carbs."}]
intensityRetentionPct: 90
frequencyReductionPct: 20

FAQ

What does the Race-Week Taper Planner calculate?: Methodology for the Race-Week Taper Planner: Bosquet 2007 meta-analysis, distance-aware depth, and Pfitzinger-style weekly structure.
What inputs does the Race-Week Taper Planner require?: It takes the following inputs: peak volume, peak intensity, taper start weeks before, race distance.
What does the Race-Week Taper Planner return?: It returns: optimalVolumeCutPct, intensityRetentionPct, frequencyReductionPct, raceDistance, taperStartWeeksBefore, weeklyPlan.
Is the Race-Week Taper Planner free to use?: Yes. It runs entirely client-side in your browser with no signup, and is also importable as an ES module engine for AI agents.
What category does the Race-Week Taper Planner belong to?: Planning. See the methodology above for formulas, assumptions, and limitations.