Men’s Health: There’s no exact number for how much deep sleep you need, but there are ways to make sure you are getting enough shuteye.

In general, if you are getting about eight hours of sleep, you can expect to cycle through the entire sleep process about four to five times a night.

“You are going to get your big doses of [deep] sleep within the first two 90-minute cycles,” says James Maas, PhD, past chairman and professor of psychology at Cornell University and author of Power SleepSleep for Success, and Sleep to Win!.

Maas prefers to call deep sleep “sound sleep,” since technically REM sleep is a deeper level of sleep than the stage that has been coined “deep sleep.” But whatever it is called, this stage and all of the others are important and have specific functions. In Stage 1, you begin dozing off and your body and brain movement begins to slow down; Stage 2 is a light sleep where you’ll experience a drop in temperature, muscle relaxation, and a slower heart rate; Stage 3 is that deep sleep, where Dr. Maas says you encounter brain and body restoration, memory consolidation, cell restoration and the removal of toxins from the brain as well as where if you are awakened you’ll feel groggy and disoriented; Stage 4 is REM (rapid eye movement) sleep, which is where you typically have really vivid dreams as well as experience paralyzes in your muscles.

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