However, if we are feeling stressed, rushed, or busy until we get into bed, our body receives signals that we do not want to go to sleep, and keeps us alert. Even if we are exhausted, what we do before we go to bed will determine whether we will be able to move from our “tired, but wired” state into a sleepy state. As we relax our bodies and minds, our brainwaves start to change from the choppy beta alert state, to the more curvy waves of alpha. It is much easier to get to sleep from an alpha state, than trying to jump straight from active beta to sleep (made up of daydreamy theta then deep sleep delta waves).
The biological master clock, or circadian rhythm, has evolved for different functions throughout each 24 hour period:
9pm: melatonin is secreted > 2am deepest sleep > 8.30am intestinal motility > 10am greatest alertness > 3pm drop in alertness > 5pm greatest muscle strength > 6.30pm highest blood pressure > highest body temperature.
The body is always trying to get back to homeostasis, where everything is in balance and health is optimised. Our autonomic nervous system moves from sympathetic (awake, alert, active) to parasympathetic (rest, digest, heal) states throughout the 24 hour period.
Many people sabotage their sleep by using bright lights until bedtime, or drinking too much caffeine during the day, a nap in the afternoon or even taking cardio exercise in the evening.