Most people naturally wake up within one to three hours of sunrise, aligning with low adenosine levels and the release of cortisol and epinephrine.

“It's very important that that cortisol pulse come early in the day, or at least early in your period of wakefulness.”

“When you wake up in the morning, you wake up because a particular hormone called cortisol is released from your adrenal glands. Your adrenal glands sit right above your kidneys and there's a little pulse of cortisol. There's also a pulse of epinephrine, which is adrenaline from your adrenals and also in your brain. And you feel awake. Now, that pulse of cortisol and adrenaline and epinephrine might come from your alarm clock. It might come from you naturally waking up. But it tends to alert your whole system and your body that it's time to increase your heart rate. It's time to start tensing your muscles. It's time to start moving about.”