Sleep debt

What it is

Sleep debt is the accumulated gap between the sleep you need and the sleep you get. One short night adds a little. A week of short nights adds a lot.

Why it matters for training decisions

In a well-known laboratory study, healthy adults who were limited to 6 or 4 hours in bed a night for 14 days built up steadily worse thinking and reaction performance. Yet their own ratings of sleepiness rose only a little after the first few days. In other words, people get used to feeling slightly tired while their performance keeps slipping.

The American Academy of Sleep Medicine and Sleep Research Society recommend that adults sleep 7 or more hours a night on a regular basis. The 2021 athlete consensus notes that many elite athletes habitually sleep less than 7 hours, and that in the wider population, regularly sleeping under 7 hours is linked to a higher risk of respiratory infection. It also says a one-size-fits-all number is unlikely to suit every athlete, so your own sleep need matters.

How wearables measure it, and the limits

Some devices estimate a nightly sleep need and track the shortfall. Others just show duration. Either way, the number depends on how well the device detects sleep and wake, and on how it estimates your need, so treat it as a guide.

How P247 uses it

P247’s sleep plan adjusts the bedtime it suggests for the coming nights for your training load and recent sleep debt. Sleep duration is also one of the inputs to the daily recovery score.

This glossary is general information to help you understand your training data. It isn't medical advice, diagnosis or treatment. For injury, illness, medication, blood test results or any health concern, speak to a qualified health professional.

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