I missed a week. Pick up or restart?

The short answer

Pick up. Rejoin the plan where the plan is. Do not restart, and do not try to make the week up.

What a week off actually costs

Under two weeks is mainly cardiovascular, and it reverses quickly.

The specific thing that happens is a drop in plasma blood volume, which falls within days and recovers within one to two weeks. This is why the first ride back feels so much worse than it should: your heart rate runs high at a given power and everything feels laboured. That sensation is not lost fitness. It is a temporary and rapidly reversible change in blood volume.

Beyond two weeks, deeper muscle-level changes begin. Mitochondrial density and enzyme concentrations start to move. A planned one to two week break sits well inside the reversible zone. A month-long break is a different question and does need a deliberate rebuilding phase.

Why restarting is the expensive option

If you go back to week one, you spend several weeks training below the level you are already at. That is a maintenance stimulus rather than a progressive one. You would be rebuilding something you never lost, and the weeks you spend doing it are weeks you are not progressing.

There is also a compounding effect worth knowing about. Long-trained cyclists lose fitness slower and regain it faster, because myonuclei added through years of training persist through detraining and enable faster re-adaptation. The longer you have been riding, the less a week costs you and the less a restart makes sense.

The thing that actually goes wrong

It is almost never the missed week. It is what happens next.

Cramming. Compensating with extra load is how a missed week becomes an injured month. Compressing training into fewer days means each stimulus arrives before recovery from the previous one has completed, so you accumulate fatigue without collecting the adaptation. You get the cost and not the return.

Restarting. Throwing away real fitness out of an instinct that you have to earn it back.

All-or-nothing thinking. Deciding the week is ruined and doing nothing at all. Completing seventy percent of planned load is a productive week, not a failure.

So what do you actually do

Look at what this week's plan says and do that. If the first session back is a hard one and you feel flat, soften it, but do not go looking for the sessions you missed. They are gone, and they were not worth what recovering them would cost.

Where this changes

• Injury or illness. Get medical clearance before returning, and address the cause rather than only the symptom, or recurrence is likely.
• A month or more off. Now you want a deliberate return structure: zone 2 only for the first two weeks, extending duration in weeks three and four, and one quality session a week from week five.
• If the week off was because you were run down, the missed week may have been the recovery you needed. Do not immediately spend it.

The one-line version

A week is inside the reversible zone, restarting costs more than the week did, and the danger is entirely in what you do next.