Coach! What Should I Do?

“I only slept for four hours. I have a hard session prescribed today. Should I still do it?”

Move the hard session. Four hours' sleep does not automatically mean doing nothing, but it is a poor moment to force important intensity simply because it is still written down.

The session has not changed. The athlete who is meant to complete it has.

Start with safety. Then decide whether an easy, low-risk session would still serve a purpose or whether rest is the better choice. The aim is not to rescue today's completion score. It is to protect the purpose of the training and your ability to execute the work that matters.

Why I would move the hard session

A hard session only earns its place when you can execute it well enough to create the intended training stimulus and recover from it well enough to keep progressing.

After one short night, you might still be physically capable of starting—and even finishing—the session. That does not make it the best decision.

In a small randomised study, ten men completed performance tests after normal sleep, total sleep deprivation and a four-hour sleep opportunity. After the four-hour condition, the researchers reported likely reductions in performance during a 15-minute all-out cycling test and a countermovement jump. The study is too small and specific to predict exactly what will happen to you, but it gives us a useful warning: one short night can make demanding work less productive.

Another randomised crossover study followed 16 trained male cyclists after a high-intensity interval session. When their subsequent sleep was restricted to roughly half their normal time in bed—an average of 3.83 hours—their peak power had recovered less 24 hours later than after a normal night. They also reported greater sleepiness and less motivation to train during the recovery period.

Neither study creates a rule that everyone performs badly after one poor night. Both used small, male-only samples and controlled exercise tests. They do support a sensible coaching judgement: when sleep has been severely restricted, we should question the value of forcing high-quality work and consider what it may cost the next session as well as this one.

That is enough for me to move the intensity. I do not need a wearable to declare you “unready”, and I do not need to wait for a failed interval to prove that the decision should have changed.

The context that matters

Moving the hard session is the starting decision in this scenario. What replaces it depends on four things.

Are you alert enough to train safely?

If you feel sleepy, foggy or unable to concentrate, safety overrides the training schedule. Do not drive to a session when sleepy. The Highway Code says not to begin a journey when tired, and the NHS also advises against driving when sleepy.

Apply the same judgement to the training itself. Road riding, open-water swimming, heavy traffic, technical descents and unfamiliar environments leave less room for reduced alertness. Choose a safer option or do not train.

What was the session meant to achieve?

There is a difference between moving an important race-specific session and changing a routine aerobic session. Ask what the session is for, why it sits here and what quality of execution it needs.

If intensity, pace control, technique under load or a meaningful benchmark matters, poor execution can defeat the purpose. Moving the session protects that purpose; it is not avoiding the work.

What has the rest of the week looked like?

One disturbed night after an otherwise well-managed week is different from several nights of poor sleep combined with accumulating fatigue, illness, travel or unusual life stress.

The more signals that point in the same direction, the less useful it is to treat this as an isolated scheduling problem. The training may need a wider adjustment rather than a single swap.

What comes next?

Moving a session is not the same as squeezing it into the first empty space. Look at the following 24 to 48 hours. A hard session moved too close to another priority session may simply create a second poor decision.

Work backwards from the most important training ahead. You may move the intensity, replace another session, reduce the week's total work or decide that this particular session no longer earns a place.

What I would do today

I would make the decision in this order:

  1. Do not train or travel if you cannot do so safely. Sleepiness that affects concentration is not something to prove your way through.
  2. Move the hard session. Do not turn the warm-up into a test of whether you can bargain your way back to the original prescription.
  3. Choose between easy movement and rest. If you feel alert, are otherwise well and can train in a low-risk setting, a short easy session may still be useful. If it has no clear purpose or you feel profoundly tired, rest.
  4. Review the next two days before rescheduling. Put the hard work where it can be executed and recovered from, even if that means changing something else.
  5. Tell your coach what happened. Share the amount and quality of sleep, how you feel, likely cause and any wider pattern. Useful feedback gives us something better than guesswork.

Do not try to “make up” the missed intensity by adding extra work to the next session. The goal is to restore useful training, not repay a debt to the calendar.

What could change the answer?

If “four hours” means an inaccurate estimate but you feel alert, otherwise well and the planned work is genuinely easy and low risk, training may still be reasonable. The answer changes because the purpose and cost of the session are different—not because four hours has become an acceptable target.

If poor sleep is recurring, affecting daily life or leaving you constantly tired during the day, this is no longer just a decision about today's session. The NHS advises speaking to a GP when sleep problems have lasted for months or are making daily life difficult. Snoring, interrupted breathing during sleep or suddenly falling asleep also deserve appropriate professional attention.

This article assumes a generally healthy athlete dealing with a one-off poor night. It is general coaching information, not an assessment of a sleep disorder, illness or medical symptoms. If something about your health or safety concerns you, seek advice from an appropriately qualified healthcare professional.

The principle to carry forwards

Protect the purpose, not the calendar.

Consistency is not the ability to complete every prescribed session regardless of context. It is the balance between useful execution and recovery that lets you keep doing the right work over time.

The hard session still matters. That is exactly why I would move it.

Between Sessions

Training decisions rarely happen in perfect conditions. Between Sessions is my personal letter about the context, questions and lessons that sit between the prescribed work.

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