Understanding the sleep graphs on your fitness tracker

As a lover of sleep, one of my favourite features of my fitness tracker is the sleep tracker app. In this blog post, we explain how to read the sleep cycle calculator.

Understand your sleep cycle

There are four stages of sleep: Stage 1, 2, 3 and 4 (REM- Rapid Eye Movement). There’s a five to 15 minutes interval between each stage of sleep, and a sleep cycle spans between 90 to 110 minutes. Stage 1, 2 and 3 are called the Non-Rapid Eye Movement Stages (NREM).

A sleep cycle is the transition between the Non Rapid Eye Movement to the Rapid Eye Movement phase of sleep. There are about four to five sleep cycles per sleep time and each cycle lasts for about 90-120 minutes, which are usually clearly separated on your sleep tracker app.

Stage 1 is the “transitional phase” of sleep, basically when you’re feeling drowsy. Eye movement at this stage of sleep is slowed down and your muscles become more relaxed. However, you can be easily awoken in this stage. This is also when your muscles will jerk, sometimes waking you up again.

Stage 2 is the defining phase of the NREM stage of sleep and about 50% of the time spent sleeping is in this stage. Your body temperature cools down and your heart rate slows. Your brain activity slows down with occasional burst of activity, or waves, called “sleep spindles”.

Stage 3 is characterised by Delta/Slow Waves. Deep sleep begins here and the body is less responsive to the surrounding environment. This stage of sleep only makes up about 20% of your time sleeping. The following are experienced in this stage of sleep:

  • Muscle and tissue repair
  • Growth and development
  • Immune system boost
  • Parasomnias (sleep walking, sleep talking)

REM (REM- Rapid Eye Movement) stage is characterised by increased brain activity. If Stage 3 is about rest and regeneration, stage 4 is all about energizing your body. Awakening and arousal is common place at this stage of sleep. Also, this is the phase where dreaming occurs. The following are experienced in this stage of sleep:

  • Increased heart rate
  • Increased blood pressure
  • Faster breathing
  • Consolidation and processing of information by the brain

The benefits of good sleep

Good sleep helps to improve your health, with increased mental and physical performance. Fitness trackers and/or a sleep tracker app can establish the connection between sleep, weight gain/loss, blood pressure as well as heart rate from the data generated.

If you analyse your sleep pattern and it’s clear that you’re not getting a solid night’s sleep, it might be time to start thinking about your sleep routine and your sleep environment. When was the last time you replaced your mattress? Ideally, you should replace your mattress every 10 years.

Other aspects to consider are the amount of light in your bedroom, how much time is spent on screens before bedtime, and how warm or cold you are during the night.