Tired, but not fall-into-bed-snoring-with-half-your-clothes-on tired? Try taking a warm shower or bath before hitting the hay. Coming out of a warm shower and into a cooler bedroom will cause a slight decrease in body temperature, a drop that scientifically helps trigger a tranquil, drowsy feeling by slowing down essential metabolic activities. Or, worst-case scenario, the slumberer will go to bed feeling so fresh and so clean... clean.
When body temperature begins to fall, we start to feel tired, drowsy, and lethargic due to a natural decrease in metabolic activity. The cooler we are, the slower our body wants to do essential things like breathe and pump blood. Decreasing body temperature is one of several ways the body tells itself that it’s time to rack out (I’m running out of idioms for going to sleep). However, cooling down at night can prove difficult in hot, muggy environments where the air tends to stay at or above average room temperature (roughly 72°F). Taking a warm shower and then hittin’ the sack helps the body decrease its temperature when it might otherwise have a tough time doing so. Bottom Line: A warm shower helps initiate that sleepy, tired feeling prior to bed time because the resulting drop in body temperature slows down metabolic functions like heart rate, breathing, and digestion.
The warm water also dilates blood vessels, allowing more blood and oxygen flow into tight, stressed out muscles throughout the body . Releasing muscle tension keeps the body relaxed and comfortable, a feeling that further signals the brain it’s time to start winding down and preparing for sleep. Of course, it’s up to the individual to listen to these sleep indicators and go to sleep when needed. So taking a shower at 10:30pm then going to the bar and buying a few rounds of vodka-Red Bulls won’t make for a smooth transition to slumber-ville (though that doesn't sound like a pretty good start to a different kind of night). However, taking an extremely hot shower for too long may hinder the onset of sleep by raising body temperature too much, creating a sprightly, energetic feeling by speeding up the body’s metabolic pathways.
Temperature as a universal resetting cue for mammalian circadian oscillators. Prevent this by keeping showers between 5 to 15 minutes with the water staying at or below normal hot tub temperature (104°F). Also try gradually turning the water temperature down near the end of a pre-bed shower.