Topic Guide

Sleep — Complete Guide

Sleep is where most of your recovery, immune function, and biological aging actually happen. Wearables now track stages, debt, and timing in real detail — but the numbers only help if you know what they mean. This page collects everything we have written about sleep, from the basics of the four stages to chronotype timing.

Start here — foundational reading

Article · 5 min

Sleep Debt Science

What sleep debt actually is, why one weekend can not fix five short nights, and how it accumulates.

Article · 4 min

Your Chronotype Matters

Skylark vs. owl is not a personality quiz — it determines when you should sleep for best recovery.

Core concepts

The four stages, what each does for your body, and how wearables detect them.

Sleep Quality Score

What the number on your watch actually combines — and what it ignores.

Sleep Efficiency

Time in bed vs time asleep — why the ratio matters more than total hours.

Evidence-based practices that move the needle — and the popular ones that do not.

Calculators & tools

Sleep Need Calculator

Find your optimal bedtime and wake time based on cycles, age, and goal.

Circadian Rhythm

See how light, food, and timing align — or fight — your body clock.

Related topics

Heart Rate Variability

HRV during sleep is the best window into recovery — closely tied to sleep quality.

Recovery & Training

Sleep is the biggest single input to recovery — see the full picture.

MyBodyAI tracks your sleep across providers and surfaces the trend that wearables rarely show — sleep debt building up across weeks.

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