Freerunning sleep facts for kids

Freerunning sleep is when your sleep schedule isn't set by the usual 24-hour day and night cycle. Think of it like your body's internal clock running on its own, without being "tuned in" to the outside world. Sometimes, people also use the term for sleep that follows a natural 24-hour rhythm but isn't forced by things like alarm clocks.

How Scientists Study Freerunning Sleep

Scientists often study freerunning sleep in animals. They keep animals in special laboratory settings where conditions are always the same, like constant light or constant darkness. This way, the animals can't tell what time it is outside. When this happens, their bodies follow their own internal clocks, called circadian rhythms.

For example, an animal's natural circadian rhythm might be a bit shorter or longer than 24 hours. If an animal's natural cycle is 23 hours, its sleep and wake times will shift earlier each day compared to a normal 24-hour clock. If its cycle is 25 hours, its times will shift later. This means their sleep schedule "freeruns" and doesn't match the actual time of day.

Scientists do experiments to find out what signals can help "reset" or "tune in" these internal clocks. They also check how much an animal's clock can be adjusted. For instance, some animals can get used to a 22-hour day, but not a 20-hour day.

What Signals Affect Sleep?

The most powerful signal for setting an animal's internal clock is light. But other things can also help:

• The timing of meals can be a signal for some animals.
• Exercise can also help set the clock for certain animals.
• Heat doesn't seem to affect sleep timing.

Scientists have also studied freerunning sleep in people. In some research studies, people stay in a lab with very dim light and no idea of the actual time. These studies show that, on average, adults have a natural circadian cycle of about 24 hours and 11 minutes.

Freerunning Sleep in People

Sleep Disorders

Some people have a circadian rhythm sleep disorder that causes them to freerun all the time. This happens even if they spend time in daylight and eat meals at regular times. Many people with this condition are blind, but some can see. Their internal clocks often have a longer cycle than 24 hours, and they can't easily adjust to the outside world. Scientists are still trying to understand why this happens.

Choosing to Freerun

Some people believe they will be more healthy if they don't stick to a strict sleep schedule. They try to go to bed only when they feel sleepy and don't use alarm clocks. They might call this "freerunning." However, since they are still exposed to daylight and darkness, their sleep is usually still influenced by the 24-hour cycle, unlike the true freerunning seen in lab animals kept in constant conditions.