Melatonin

Melatonin is the hormone the pineal gland releases at night that signals sleep. The body produces it in the dark and shuts it down at first light.

In the lean context, melatonin is the lever that opens the deep-sleep window where recovery actually happens. When melatonin fires on time, sleep arrives cleanly and the night is restorative. When it fires late or weak, sleep onset stretches, the deep-sleep window narrows, and the next day's training and discipline both come back light.

The body times melatonin from contrast. Bright daylight on the eyes during the day primes the evening release. Dim light in the hours before bed lets it climb. Indoor mornings flatten the daytime peak. Screen-lit evenings push the climb later. Both ends of the rhythm need to hold for the signal to land on time.

What raises it

• Sun exposure. Bright daylight during the day primes the contrast that triggers nighttime release. Days lived indoors blunt the evening climb.
• Circadian rhythm. A clock that fires on time releases melatonin on time. A regular bedtime gives the body a window to expect.
• Sleeping. A consistent sleep schedule reinforces the same daily rhythm that times melatonin release.

What lowers it

• Alcohol. Drinking suppresses REM and disrupts melatonin signaling through the second half of the night, even at moderate doses.
• Sugary drinks. Late caffeinated sodas and sweetened coffee drinks delay the time melatonin would otherwise rise. Even decaf with sugar fragments the second half of sleep.