Marathon Taper from 90 km Peak: A 2-Week Volume Reduction Plan

The taper is one of the most-debated parts of marathon training: too long and fitness slides; too short and the runner arrives over-fatigued. The published meta-analyses converge on a 2-week structure with a sharp volume reduction in the final week. This is the worked-case entry in the marathon-execution track of our race-prediction series: it applies the taper curve to one concrete high-volume runner. Here is what the engine returns for a representative 90 km/week peak runner.

The scenario

A trained marathoner with a peak weekly volume of 90 km. Two intensity sessions per week throughout the build (tempo plus VO2 work). Wants the optimal volume reduction pattern for the final 2 weeks before a marathon, including the long-run length for the pre-race weekend.

What the calculator returns

Running the inputs through the Race Week Taper tool:

# race-week-taper (computed live from /engines/race-week-taper.js)
Engine input
  peak_volume           = 90
  peak_intensity        = 3
  taper_start_weeks_before= 2
  race_distance         = marathon

Engine output
  optimalVolumeCutPct   = 55
  raceDistance          = marathon
  taperStartWeeksBefore = 2
  weeklyPlan[0].weekFromRace= 2
  weeklyPlan[0].volumeKm= 50.4
  weeklyPlan[0].volumeCutPct= 44
  weeklyPlan[0].intensitySessions= 3
  weeklyPlan[0].longestRunKm= 22.7
  weeklyPlan[0].notes   = Keep the pace of quality sessions and the number of runs; shorten the reps, easy runs and long run.
  weeklyPlan[1].weekFromRace= 1
  weeklyPlan[1].volumeKm= 30.6
  weeklyPlan[1].volumeCutPct= 66
  weeklyPlan[1].intensitySessions= 2
  weeklyPlan[1].longestRunKm= 13.8
  weeklyPlan[1].notes   = Race week: every usual run, all short, with a few race-pace strides; nothing new, sleep and carbs first.
  intensityRetentionPct = 100
  frequencyReductionPct = 0

Two weekly templates. Two weeks out, volume drops 44% to 50.4 km with a 22.7 km long run and all three quality sessions kept at their usual pace. Race week drops 66% to 30.6 km (the race not included), with two short quality sessions and a 13.8 km longest run. The two weeks average the 55% headline cut.

Reading the numbers

The cut deepens into race week: 44%, then 66%. This follows the Bosquet/Mujika meta-analysis, where a progressive 41 to 60% volume reduction over about 2 weeks, with intensity and frequency unchanged, produced the largest performance gain on race day^[1].

Two-week taper math
  Pre-taper weekly volume        90 km
  Two weeks out                  50.4 km   (44% cut = 0.8 × 55%)
  Race week                      30.6 km   (66% cut = 1.2 × 55%, race not counted)
  Average cut                    55%

  Longest run (45% of the week):
    Two weeks out                22.7 km
    Race week                    13.8 km
    Race day                     42.195 km

Frequency:
  Pre-taper                      6 runs/week
  Taper weeks                    6 runs/week (each one shorter)

The 22.7 km long run two weeks out is the last moderate long run of the cycle. Race week's 13.8 km longest run is a ceiling, not a target: enough to keep stride mechanics without adding fatigue, and many runners keep it shorter.

Where the formula breaks

Low-volume runners taper too much. A runner at 50 km/week peak gets the same 66% race-week cut, which leaves 17 km. That can feel lethargic; many low-volume runners do better nearer 25 to 30 km with the same intensity touches. The engine scales the cut by race distance, not by training volume.

High-volume runners taper too little. A runner at 130 km/week peak benefits from a 3-week taper rather than 2 weeks. The accumulated fatigue from sustained high mileage takes longer to clear. Above 100 km/week peak, push the taper start to week -3.

The intensity assumption. The engine assumes the runner's peak weeks include 2 to 3 intensity sessions. A "long, slow, easy" marathon build with no quality work does not need the same intensity retention; in those cases, 2 light hard sessions during the taper add stimulus that was missing rather than maintain fitness.

The race week itself

The engine's week -1 prescription expands into a day-by-day plan:

Mon (race -6)    4 km easy + 4 × 100 m strides
Tue (race -5)    6 km easy + 5 × 30 sec @ marathon pace
Wed (race -4)    Off, or 30 min easy spin
Thu (race -3)    4 km easy + 4 × 100 m strides
Fri (race -2)    3 km easy + 3 × 100 m strides
Sat (race -1)    Off, or 20 min easy shakeout
Sun              RACE
                                                              ≈ 17 to 20 km total
                                                              + race

Short runs every day except Wednesday and Saturday. Strides keep neural patterns sharp without adding fatigue. This sample sits well under the engine's 30.6 km race-week ceiling; a runner who feels flat on that little can extend Tuesday and add an easy run on Wednesday without leaving the plan.

Sleep, hydration, and stress during taper

The taper is also a behavioral block, not just a training block. Three high-impact practices:

• Add 30 to 60 min of sleep per night. Sleep is when most of the supercompensation actually happens; running 8 to 9 hours instead of the usual 7 to 7.5 maximizes the adaptation window.
• Hydrate a little more than usual in the final week. Marathon-day glycogen storage binds water, so topping up fluid in the taper week (a few hundred extra millilitres a day is a reasonable starting point) helps the muscle stock more glycogen; under-hydration tends to show up as a kilogram or two of "missing weight" on race-day morning compared to a properly-loaded runner.
• Avoid new stressors. No new shoes, no new race-day nutrition test, no travel that breaks sleep patterns past 1 hour. The body's adaptation system is already busy.

Cross-checking against carbohydrate loading

The taper week is also the carb-loading window. Standard sports-nutrition guidance for the 24 to 48 hours before an endurance event puts daily carbohydrate in the region of 7 to 10 g/kg of bodyweight; treat that as a target range and individualise it. Pair the taper with the Macro Cycling Calculator for a race-week macro plan. Under-eating during taper is the most common race-week error; the body is doing less work but needs more substrate to top off muscle glycogen.

Related tools and follow-ups

• Race Week Taper — the engine used here.
• Running Pace Calculator — convert race-pace targets into per-kilometer splits.
• Marathon Pace Elevation — final course-specific pacing plan.

Related in this series

• The Marathon Taper — the taper pillar: the full volume-reduction curve and the evidence behind it.
• Sweat-Rate Fueling for a Warm Marathon — the hydration side of race-day execution.
• Race Time Prediction: Riegel and Its Limits — the prediction pillar that sets the goal time.
• Marathon Pace Elevation — the pacing pillar: slope correction for hilly courses.

Beyond the series: How to plan a deload week covers the broader recovery-cycle framework.

FAQ

How much should you cut volume in the marathon taper? The engine returns an average volume cut of 55% for a 2-week marathon taper from 90 km/week peak. Two weeks out drops 44% to 50.4 km with a 22.7 km long run; race week drops 66% to 30.6 km, not counting the race.

Should intensity drop during the taper? No. Following Bosquet 2007, the engine keeps intensity at 100% through the taper: keep race-pace and tempo sessions at their usual pace and reduce only their duration. The meta-analysis found the best results when intensity and training frequency were left unchanged.

How long should a marathon taper be? 2 weeks for trained marathoners is the central recommendation. 3 weeks works for high-mileage runners (over 100 km/week peak); 1 week works for lower-mileage runners (under 50 km/week peak). The 90 km/week peak in this case sits squarely in the 2-week band.