What do the sleep stages mean?

Not all sleep is created equal. Your AlterMe app breaks your night into stages — each serving a different role in your recovery.

How long it took you to fall asleep. A shorter Wind Down time generally means your body was ready for sleep. Consistently long Wind Down times can be a signal worth paying attention to — stress, caffeine, alcohol, and late-night screen use are common contributors.

The transitional stage that makes up the largest portion of your night. Your body is either winding down into deeper sleep or cycling back up toward wakefulness. Less restorative than deep or REM, but a necessary part of healthy sleep architecture.

The most restorative stage of sleep. During deep sleep, heart rate and breathing slow, movement stops, and your body activates the physiological repair mechanisms that drive recovery from training and stress — tissue repair, immune function, and memory consolidation. Most deep sleep happens in the first half of the night. AlterMe uses 15% of your total sleep as a healthy deep sleep benchmark. For an 8-hour night, that's around 72 minutes. Consistently falling short of this is worth paying attention to — it's one of the factors that influences your readiness score each morning.

Short for Rapid Eye Movement. Your brain is highly active — processing emotions, consolidating learning, and supporting mental recovery. REM sleep tends to increase in longer sleep cycles, which is why cutting sleep short often means losing the most mentally restorative stage.

AlterMe uses 20% of your total sleep as a healthy REM benchmark. For an 8-hour night, that's around 96 minutes. Like deep sleep, your REM proportion is one of the signals that shapes your readiness score each day.

Brief periods of wakefulness during the night. These are normal and most people don't remember them. A few short awake periods per night is typical — it only becomes a concern when they're frequent, long, or leaving you feeling unrested.

Your sleep stage breakdown feeds directly into your readiness score each morning — which in turn shapes your AlterMe daily recommendations. It's not just about how long you slept, but how well.