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Biological rhythms: definition, types and operation

Biological rhythms: definition, types and operation

February 29, 2024

Surely all of us have heard at some time in our lives that people are animals of customs. This expression, in addition to certain, hides an infinity of processes that our body performs to keep those customs at bay.

These processes refer to the biological rhythms , which determine practically all the main activities of our organism, from the need of sleep, the sensation of hunger or the rhythm with which we blink.

Related article: "The 9 stages of the life of human beings"

What are biological rhythms?

By biological rhythms are understood the oscillations that occur levels and physiological variables within a time interval, these oscillations depend on a chronometer or internal clock and external or environmental variables that intervene in their synchronization.


Habits and activities both human and animal always have a rhythm and a regular harmony. To put it in a way, living implies a rhythmic phenomenon that marks us when we eat, when to drink, when to sleep, etc.

In this way, if we stop to think about the relationship between a habit or body habit and its relationship with time , we can observe that all of them happen in a cyclical order or cadence which makes us think that something exists in our organism, or outside of it, which is in charge of regulating them.

The external agents that regulate our daily habits are much more common than what is sometimes thought. The environment, the seasonal changes, the hours of light or the cosmic changes such as the lunar phases play a very important role when regulating the activities of our organism.


The main internal structures involved in this regularization are the nervous system and the endocrine system, which are influenced by these external agents. However, there are a series of internally controlled rhythms such as heart rhythms or breathing times, this other type of rhythms must be classified in a separate group due to its endogenous nature.

Types of biological rhythms and functionality

As mentioned above, chronobiology distinguishes up to three types of biological rhythms according to their duration. These rhythms are called: circadians, infradians and ultradians .

1. Circadian rhythms

Taking into account the etymological origin of this term: circa-around and dies-day; we can correctly assume that circadian rhythms are those needs or bodily habits that occur every 24 hours approximately.


The best known and most illustrative example are sleep cycles. Usually the need for sleep usually appears at the same time and any alteration of this rhythm sometimes involves some type of disorder or sleep disorder.

If we take this example into account, it is not unusual to think that these habits depend to a large extent on external regulatory agents such as daylight. Hence, it is always recommended to sleep in complete darkness because even artificial light can alter our sleep cycles.

Such is the influence of these exogenous regulators that even influence the course of some diseases or psychological conditions. In the case of depression disorder, it is common for people to report a worsening of psychological symptoms during the first hours of the day, which moderate throughout the day.

2. Infradian rhythms

By infradian rhythms understand all those habits and activities of the body that occur with a cadence less than 24 hours, that is less than once a day . Although this may seem strange there are certain body habits that work with these oscillations.

The most common example is the menstrual cycle, since it is completed once every 28 days. Other phenomena that occur with a cadence similar to that of the menstrual cycle are the lunar cycles and the tides, for that reason in many occasions an attempt has been made to establish an influence of the lunar phases in the different stages of the cycles of the women.

However, this relationship has never been scientifically proven. Those who defend it justify this impossibility on the basis that there are many day-to-day factors that interfere in the coordination of both rhythms.

3. Ultradian rhythms

Although less known and less subject to external influences there is a series of rhythmic movements that occur with a frequency of more than one every twenty-four hours.

These rhythms are the beating of the heart, blinking, the rhythm of breathing, or REM sleep cycles that occur every 90 minutes.

How to maintain the biological rhythms

As discussed above, given that these biological rhythms are conditioned by numerous external and environmental factors can be easily altered as a result of any change, either in the environment or due to a change in our daily routine.

To avoid the possible consequences of these variations in our biological rhythms (insomnia, change of smoke, changes in appetite, etc.) It is convenient to maintain a daily routine that allows us to maintain our energy.

Below are a series of recommendations to keep our biological rhythms intact.

1. Get up and go to bed at the same time

As much as possible it is convenient to start or end our day always at the same time or, at least, at approximate times. The moment we wake up marks the beginning of the activation phase of our bodies.

However, it is also necessary to perform a few minimum hours of sleep. That is, if one day we go to bed later than usual for whatever reason, it is better to do the recommended 7 or 8 hours of sleep before getting up too early just to meet the schedule.

2. Keep the routine even on vacation

Although it seems unappetizing, it is advisable to keep our usual hours even during the holidays . In this way we will keep our biological rhythms practically intact and it will be much easier for us to conserve energy once they are finished and we have to return to the routine.

If necessary, a relatively structured schedule can be carried out and planned in advance, so that the increase of free time does not cause us to postpone tasks whose regularity must be strengthened.

3. Always eat at the same time

Like sleep, the sensation of hunger is also subject to a temporary cadence . In addition, all biological functions depend on how we nourish ourselves and when we do it, so that failures in eating and the regularity with which we eat can create a chain effect. Therefore, it is essential to maintain stable schedules for the main meals. In this way, we will control the sensation of hunger and avoid binge eating.

4. Keep an agenda or diary with our habits

If we monitor our activity or daily habits, it will be easier for us to fulfill all those obligations or objectives that we consider day to day. Therefore, avoid imbalances and irregularities pronounced in the organization of our week will favor the establishment of healthy and consistent biological cycles.

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