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= 90
  weeklyPlan[0].volumeCutPct= 0
  weeklyPlan[0].intensitySessions= 2
  weeklyPlan[0].longestRunKm= 40.5
  weeklyPlan[0].notes   = Cut weekly long run by ~25%; keep intensity sharp but shorten reps.
  weeklyPlan[1].weekFromRace= 1
  weeklyPlan[1].volumeKm= 36
  weeklyPlan[1].volumeCutPct= 60
  weeklyPlan[1].intensitySessions= 2
  weeklyPlan[1].longestRunKm= 16.2
  weeklyPlan[1].notes   = Race week — short shakeout efforts, no new stimulus, prioritize sleep and carbs.
  intensityRetentionPct = 90
  frequencyReductionPct = 20

Two weekly templates. Week -2 holds the same overall weekly volume (90 km) but cuts the long run from typical 42+ km down to 40.5 km. Week -1 drops to 36 km — a 60% volume reduction — while retaining two short intensity sessions and a 16.2 km longest run on the weekend before race day.

Reading the numbers

The volume reduction curve is steep in the final week and modest in the second-to-last week. This matches the published recommendation from the Bosquet/Mujika meta-analysis: 41 to 60% volume reduction across 2 weeks produces the largest performance gain on race day^[1].

Two-week taper math
  Pre-taper weekly volume        90 km
  Week -2 weekly volume          90 km     (no cut, but shorter long run)
  Week -1 weekly volume          36 km     (60% cut)

  Long run sequence:
    Week -3                      45 km     (peak long run)
    Week -2                      40.5 km   (10% cut from peak)
    Week -1                      16.2 km   (60% cut from week -2)
    Race day                     42.195 km

Frequency:
  Pre-taper                      6 runs/week
  Week -1                        ~5 runs/week (20% reduction)

The week -2 long run at 40.5 km is the last "fitness" stimulus of the cycle. Week -1's 16.2 km longest run is a "shake-out" — enough to maintain stride mechanics without adding fatigue. Some runners cut this further to 12 to 14 km; the published recommendation lands around 16 km for a 90 km/week peak.

Where the formula breaks

Low-volume runners taper too much. A runner at 50 km/week peak does not need a 60% reduction in the final week. Cutting from 50 km to 20 km feels lethargic; better to drop to 30 to 35 km with the same intensity touches. The engine's 55% cut is calibrated for mid-volume marathoners.

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. The 19 to 22 km of pre-race running matches the engine's 16.2 km longest weekly run plus shorter sessions on other days.

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 optimal volume cut of 55% for a 2-week marathon taper from 90 km/week peak. Week minus 2 holds 90 km with the long run cut by 25%; week minus 1 drops to 36 km (60% cut).

Should intensity drop during the taper? No. The engine returns 90% intensity retention through the taper. Keep race-pace and tempo sessions sharp; reduce only the duration. Cutting intensity along with volume causes performance regression on race day.

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.