Taper is the phase where months of training either pay off or fall apart. You've done the work. The fitness is built. What happens in the final 2–3 weeks before your race determines whether that fitness shows up on race day — or stays buried under fatigue.
Most runners understand taper poorly. They either cut too much (losing sharpness), cut too little (arriving fatigued), or panic halfway through and add training back when the discomfort becomes too strange to tolerate.
I've done all three. The taper that finally worked wasn't the one where I felt best going in — it was the one where I trusted the data over my legs.
What taper actually does
Taper is not rest. It is a deliberate reduction in training volume — while maintaining intensity — designed to accomplish one specific thing: arrive at race day with high CTL and low ATL.
The math of CTL, ATL, and TSB:
- CTL (fitness) is a 42-day rolling average. It falls slowly when you taper — roughly 1–2 points per week.
- ATL (fatigue) is a 7-day rolling average. It falls quickly when volume drops — sometimes 5–10 points in a single easy week.
- TSB (form) = CTL − ATL. As ATL falls faster than CTL, TSB turns positive.
Target on race day: TSB +10 to +20. That window represents peak readiness — maximum fitness expression with minimum fatigue interference.
A runner who skips taper arrives at the start line with TSB −25. A runner who tapers well arrives at TSB +15. Same fitness base, 15–25% difference in how much of that fitness actually shows up in the race.
The taper timeline
Week 1: Volume drop, intensity maintained
Reduce total weekly volume by 20–30% compared to your peak week. The reduction comes from shortening easy runs and eliminating secondary quality sessions — not from removing intensity altogether.
Keep one quality session at your race-relevant paces: a medium-length tempo, or a set of marathon-pace miles in a long run. Your VDOT-derived paces don't change — you just do less of them.
ATL starts falling. TSB begins turning. You may feel slightly flat or oddly energetic — both are normal responses to the load shift.
Week 2: Volume drops further, sharpness preserved
Reduce volume another 20–30% from week 1 (40–50% below peak). Long run shortens significantly — 25–28 km for marathon (down from 32–35 km at peak). Easy runs become genuinely easy and brief.
One final quality session early in the week: 4–6 × 1 km at I pace, or 4–5 km at T pace. After this session, no more hard efforts. The adaptation window is closing.
This is where taper madness peaks. Legs feel heavy, motivation is low, minor aches appear from nowhere. ATL is dropping faster than your neuromuscular system has adjusted to. It feels wrong. It is correct.
Race week: Shake-out only
Volume drops to 25–30% of peak. Three or four easy runs of 30–45 minutes, with 4–6 strides at the end of one session to remind your legs what fast feels like.
No new stress. No compensatory training. No "last hard session" on Tuesday because you're feeling good. Feeling good is the taper working — adding training now resets ATL upward and undoes two weeks of careful fatigue management.
Taper madness: what's actually happening
The symptoms are real. The interpretation is wrong.
Heavy legs — ATL falls faster than your neuromuscular system adapts. Muscles accustomed to daily loading feel unresponsive. This resolves in the final 48–72 hours before race start.
Phantom niggles — Reduced training volume means more time to notice minor sensations that were always there but masked by training fatigue. Almost none of these are actual injuries.
Motivation drop — High training load produces endorphin response. Taper removes the stimulus. The flatness is neurochemical, not motivational.
Fear of detraining — CTL does fall during taper — by 3–5 points over 3 weeks for most runners. This is unavoidable and acceptable. The fitness gained over 16–20 weeks does not disappear in 3 weeks of reduced volume. The research on detraining shows measurable aerobic decline requires 2–3 weeks of complete rest, not 3 weeks of reduced-volume training with maintained intensity.
The taper mistakes that cost races
Cutting intensity with volume. The most common taper error. Reducing volume is correct. Removing intensity entirely produces flat legs — your fast-twitch fibers and neuromuscular system need periodic stimulation to stay sharp. Keep quality sessions short but present.
Adding training when taper feels wrong. Taper madness is uncomfortable enough that many runners respond by adding runs. This is the worst possible response: it resets ATL upward, reverses TSB progress, and compounds the fatigue you were trying to shed. Trust the data, not the feeling.
Tapering the wrong amount. Runners with low peak CTL (those who trained at low volume) need less taper than runners with high peak CTL. A 3-week taper for a runner who peaked at CTL 45 will drop TSB too high and produce sluggish legs. A 2-week taper for a runner who peaked at CTL 90 is insufficient to shed fatigue. The taper length should match the training load that preceded it.
Changing everything during taper. New shoes, new nutrition, new sleep schedule, new pre-race rituals. Taper week triggers a compulsive need to optimize everything. Resist it. Taper is the worst time to introduce new variables. Sleep normally. Eat normally. Hydrate well. Nothing new on race day.
How taper should feel vs. how it does feel
| What you feel | What's actually happening |
|---|---|
| Legs are heavy | ATL falling faster than neuromuscular adaptation |
| Lost my fitness | CTL falling by 1–2 pts/week — expected and acceptable |
| Random knee ache | Sensation always present, now unmasked by reduced fatigue |
| Can't sleep | Pre-race anxiety + reduced physical tiredness |
| Should run more | Taper madness peak — do not act on this |
| Legs feel springy (day before) | ATL has cleared, CTL is high — this is the goal |
The target feeling on race morning: slightly restless, legs feel light, mild anxiety. Not flat, not tired, not "I crushed a workout yesterday." Springy and slightly nervous is exactly right.
Taper for half marathon vs. marathon
Half marathon taper is shorter because the preceding training block is shorter and peak CTL is lower.
Half marathon: 1–2 week taper. Volume reduction of 30–40%. One quality session in week 1 at goal race pace. Race week is easy running only with strides.
Marathon: 2–3 week taper. Volume reduction of 40–50% by race week. Quality sessions in weeks 1 and 2. Race week is shake-out running only.
The physiological principles are identical — reduce ATL while preserving CTL and neuromuscular sharpness. The timeline compresses because the build-up was shorter and the fatigue accumulation was lower.
Why adaptive plans taper better
Static plans give every runner the same taper regardless of their actual training load. A runner who missed three weeks due to illness arrives at the taper phase with a CTL 20 points lower than planned. The static taper — written for a CTL of 80 — is too long and too deep for a runner at CTL 60. They over-taper, arrive with TSB +30, and race with flat, unresponsive legs.
Adaptive training plans read your actual CTL, ATL, and TSB and calibrate the taper length and depth accordingly. If your CTL is lower than planned, the taper shortens. If you hit peak phase with a higher-than-expected CTL, the taper extends slightly to give ATL enough time to fall.
This is why Zarkus recalculates your taper in real time based on your Garmin data — not based on what the spreadsheet assumed you'd have built by week 16.
Taper is the last piece of periodization. Base builds the engine. Build raises the ceiling. Peak loads the system to its maximum. Taper removes the fatigue so the fitness can express itself.
Every runner who has ever raced well has tapered well — even if they didn't know it at the time.
Frequently Asked Questions
How long should a marathon taper be?
Most marathon training plans use a 2–3 week taper. Elite runners and those following Pfitzinger's Advanced Marathoning typically use 3 weeks. Runners following Daniels' plans often use 2 weeks. The right duration depends on your peak training load — higher CTL requires a longer taper window to shed accumulated fatigue while preserving fitness.
Why do I feel terrible during taper?
Taper madness — heavy legs, low motivation, phantom niggles — is caused by a mismatch between what your body expects and what it gets. After weeks of high training load, suddenly cutting volume removes the physiological stimulation your neuromuscular system has adapted to. ATL drops quickly but CTL responds more slowly, creating a disorienting gap. It feels like detraining but it isn't — fitness is consolidating, not disappearing.
Should I keep running hard during taper?
Yes, but briefly. The key taper principle is: reduce volume significantly (30–50%) but maintain intensity. Short quality sessions at T, I, and M pace keep your neuromuscular system sharp without accumulating new fatigue. Dropping intensity entirely during taper produces flat legs on race day — you lose the sharpness that hard training built.