Guide

Spring marathon training: work back from race day

A spring marathon is decided over the winter — in the dark, cold weeks between late November and February when most of the training happens. Most plans that fail don't fail on race day. They fail in January, because they were built forwards from a start date instead of backwards from the race.

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This is a planning guide, not a coaching programme or medical advice. If you are new to running, returning from injury, or have a health condition, talk to a professional before starting a marathon build.

Start from the race, not from today

Most spring marathons fall between March and May, with a cluster of big city races in April. Whatever yours is, write down the race date first and count backwards. Everything in the plan — when the long runs peak, when the taper starts, where the tune-up race goes — is positioned relative to that date, not to the day you happen to begin.

Building forwards is how you end up peaking three weeks early, or arriving at the taper with a long run you never got to.

How far out to start

Most marathon plans run 16 to 20 weeks. Sixteen is the usual minimum for someone already running comfortably three or four times a week; twenty gives room for a slower build, a bad cold, or a newer runner. If you are not currently running regularly, you want a base period of several weeks of easy running before the plan starts.

The four phases

1. Base. Mostly easy running to build frequency and time on your feet. Nothing heroic; the aim is to be able to train consistently for the next four months.
2. Build. Weekly volume and the long run grow gradually, with a lighter cut-back week every third or fourth week so the body can absorb the work.
3. Race-specific. Long runs reach their peak, and some include stretches at your goal marathon pace. A half marathon or similar tune-up fits here.
4. Taper. Two to three weeks of reduced volume so you arrive fresh — covered below.

A common failure of plans written in one go, by hand or by an AI, is proportion: base stretched across most of the runway and everything else squashed into the last few weeks. Each phase should get a sensible share of the time available. Why AI-written plans get this wrong is its own essay.

Keep most of it easy

Studies of how endurance athletes actually train (Stephen Seiler's work is the best known) find that most of their volume — often around 80% — is at a genuinely easy, conversational effort, with a smaller amount of hard work. Recreational runners tend to do the opposite: every run at a moderate "grey zone" pace that is too hard to recover from and too easy to improve much. If you can't hold a conversation on an easy run, it isn't easy.

The long-run ladder

The long run is the backbone of the plan. It should grow gradually, drop back in cut-back weeks, and peak roughly three to five weeks before race day — many plans top out between 18 and 22 miles (29 to 35 km), or around three hours on your feet. The exact peak matters less than arriving at it without having skipped rungs.

Big jumps in training load are consistently associated with injury. The popular "10% rule" for weekly increases has little direct evidence behind the specific number, but the principle — no sudden spikes — is sound.

Plan Christmas before it happens

A winter build will meet Christmas, New Year, dark evenings and probably ice. The difference between a plan that survives and one that doesn't is whether these were expected.

• Make Christmas week a cut-back week on purpose. A lighter week you meant to have is recovery. The same week unplanned feels like failure.
• Move the long run, don't drop it. If Sunday is a family day, put it on the Saturday or the Monday bank holiday — and decide which in advance.
• Have a bad-weather version. A treadmill session or a shorter loop close to home, decided before the ice arrives.

The taper

A meta-analysis by Bosquet and colleagues found the most effective tapers last about two weeks and cut training volume by roughly 40 to 60% while keeping some intensity, so the legs stay sharp. For a marathon, two to three weeks is typical. You will feel sluggish and restless. That is normal, and it is not a sign that you need one last long run.

When you miss a run

You will. Illness, work, a week of sleet. The rule is simple: never compensate — just resume. Squeezing a missed long run into the following days, or doubling up sessions, raises injury risk for very little fitness. Skip it, carry on with the plan as written, and judge the block by how many sessions you did over the month rather than whether every one happened. Consistency beats perfection, in running as in everything else.

Questions

When should I start for an April marathon? Sixteen to twenty weeks out — late November to late December for a race at the end of April.

How long is the taper? Two to three weeks, cutting volume by roughly 40 to 60%.

How long should the longest run be? Many plans peak at 18 to 22 miles, or about three hours, three to five weeks out. The gradual build matters more than the number.

What about Christmas? Plan it as a cut-back week in advance.

Should I make up missed runs? No. Skip it and carry on.

More: the evidence on tapering · why rigid streaks break people · why AI plans get periodisation wrong