Though the recommended amount of sleep per night is somewhere around eight, hours, we only spend a small portion of that time in deep sleep. “A good rule of thumb is to aim for 90 minutes of deep sleep—but the most important signal is matching your data with how you feel,” Kinnunen notes.
If you didn’t get enough, you may experience things like body aches, tight muscles, and of course, droopy eyelids and a persistent feeling of tiredness. “As you get to know your body, you’ll learn what amount of deep sleep helps you feel your best,” he adds. “Getting enough deep sleep helps you wake alert and ready to face the day.”
Certain patterns to look for include how your body feels after a hard workout, traveling, or when you feel under the weather, Kinnunen says. “If you notice your body responding by increasing your deep sleep to help you rebound faster, your body is responding to stress,” he explains, adding, “If your sleep gets disturbed and you’re not getting that restorative sleep, it could be a sign to lighten your training or take a rest day.”