Shed

Guide

Base building

Base building is the least interesting phase of training and the one that decides how good the interesting phases can be. It is also the phase most often skipped, usually by people who then wonder why their block stalled in week eight.

What a base actually is

A base is aerobic capacity and structural durability. Capacity is the size of the engine: mitochondria, capillaries, cardiac output, the ability to run at a given pace using less oxygen and less glycogen. Durability is your tissues being able to take the load without breaking.

Both respond primarily to consistent volume over time, and both are slow. Weeks of easy running produce very little you can feel and a great deal you can later use. The impatience this produces is the main reason people skip it.

Why it sets the ceiling

Speed work is a conversion process. It takes aerobic capacity you already have and makes it available at faster paces. It does not create the capacity.

That is why two runners doing the same eight week interval block get very different results if one arrived with 45 miles a week of base behind them and the other with 20. The sharpening is the same; what it has to work with is not.

It is also why blocks stall. A runner who starts intervals from a thin base improves for four or five weeks as the conversion happens, then plateaus, because there is nothing left to convert. The instinct at that point is to do harder intervals, which makes it worse.

What a base phase contains

Eight to sixteen weeks, depending on how far you are from where you need to be.

  • Mostly easy running. Ninety percent or more. The volume is the point.
  • Gradually increasing frequency, then volume. Adding a fourth or fifth run a week is a better first move than lengthening existing runs. More frequent, shorter runs build durability with less injury risk.
  • Strides, twice a week. 6 to 8 x 20 seconds at around mile pace with full recovery. They keep neuromuscular coordination alive without adding meaningful fatigue, so speed does not feel foreign when the sharpening phase arrives.
  • One light threshold session. From the second half of the base phase. 20 minutes comfortably hard. Enough to keep the threshold from drifting down, not enough to compromise the volume.
  • Hills, optionally. Short hill sprints, 8 to 10 x 10 seconds, build strength and running economy with very low injury risk. A good addition late in base.

Frequently asked

How long should a base phase be?
Eight to sixteen weeks. Longer if you are coming back from time off or building toward a substantially higher volume than you have run before.
Can I do speed work during base?
Strides and short hill sprints, yes, and a light threshold session in the second half. Full interval sessions belong in the phase after, when the base is there to convert.
How much mileage should base building reach?
Whatever your race block needs to start from, arrived at gradually. For a marathon that is usually 25 to 30 miles a week minimum, and 40 plus if you have a time goal.
Will I get slower during base building?
Your top-end sharpness dulls slightly, which is why strides are in the plan. Race fitness at the end of a base phase feels worse than it is, and it converts quickly once sharpening starts.

Stop reading. Start training.

This is the theory. Shed is the schedule.

Knowing what a threshold run is for does not tell you which Tuesday to run one, or how fast, or what to do when you miss it. Shed writes every session of your race block and adjusts it as you train. Ask it where a number came from and it will tell you.

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