Ever wondered why you only feel energized and drowsy around the same time every day? That’s the effect of your body’s Circadian Rhythm. Basically, the circadian rhythm is a 24-hour internal body cycle that regulates the wake-sleep cycle.

Adult human beings experience the biggest dip in energy somewhere between 2:00 am and 4:00 am at which time they tend to be fast asleep. A short time after lunchtime, between 1:00 pm and 3:00 pm, they crave for the second cycle of sleep in form post-lunch naps. This rhythm can be different if you are a morning person or a natural night owl. These dips and rises can be difficult to notice for an average person because we seldom catch ourselves in the act (we easily remember the time we woke up than the time we fell asleep). The profound effect of the swings of alertness and sleepiness only becomes apparent when you are deprived of sleep.

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Characteristics of the Circadian Rhythm

1. It has a free-running endogenous period that lasts about 24 hours.
2. The rhythm persists with constant conditions
3. The rhythm is entrainable. You can reset your Circadian rhythm by resetting your exposure to the external stimuli which can be light or heat) through a process referred to as entertainment. During seasons with long days and short days and vice versa, people adjust their clocks and voluntarily go to bed at specific times to offset the effects of the interruption of the usual day/night hours). Also, people who travel into different time zones (traveling that involve east-west direction and vice versa) experience jet lag.
4. The rhythm exhibits temperature compensation. Wide variations in temperature within 24 hours can alter a person’s sleepiness/alertness pattern.

Besides such things such as a change in seasons and temperature, an organism can still experience Circadian interruption because of mutation, but that’s as rare as it sounds.