It is observed during fast wave sleep. The ratio and duration of the phases of slow and fast sleep in a healthy person

Every night we all go through phases of sleep: rapid and slow sleep. Physiologically, sleep is a complex of various processes during which we can experience several cycles of these two phases.

For a long time it was believed that there was no way to study human dreams and their influence on his physiology and psyche in any way. Initially, they were studied based on a purely physical description of the processes - it was possible to determine the sleeper’s pulse, his blood pressure and his body temperature. But there was no talk of assessing the influence of sleep on mental and physical activity.

With the advent of encephalography in the twentieth century, the possibilities for understanding the processes occurring during sleep have expanded significantly.

Every night's rest is necessary for a person; to some extent, we can say that sleep is more important for a person than nutrition. A person deprived of sleep for only two or three days becomes irritable, loses emotional stability, and begins to experience memory loss. Against the background of fatigue and mental retardation due to lack of sleep, a person falls into a depressive state. It is believed that the maximum time a person can live without sleep is 11 days, after which irreversible changes occur in the brain, leading to death.

The main purpose of sleep for the body is to rest all its systems. For this purpose, the body “turns off” all senses and is almost completely immobilized.

Modern science presents sleep as a special period that has behavioral characteristics of the motor sphere and the autonomic nervous system. A feature of sleep is the alternating change of two states with almost opposite manifestations. They are called slow and fast sleep.

The surprising thing is that only together both phases - fast and slow sleep - can restore both the physical and mental strength of the body. If you interrupt the night cycle at a stage when only one of the cycles is completed, the body will not receive proper rest. The combination of fast and slow sleep renews the brain's performance and fully processes the information received during the past day. It is the complete completion of sleep cycles that facilitates the transfer of information from short-term memory to long-term memory.

In fact, a full sleep is the final stage in solving the problems of the past day and a kind of “summing up” of its results.

Also, complete and proper rest during sleep improves the health of the whole body.

The following physiological processes occur only during night rest:

fluid balance is restored and the body is cleansed by removing excess moisture;
collagen protein is synthesized, which plays a major role in strengthening joints, blood vessels and skin;
The body absorbs calcium, which is necessary for bone and dental tissue.

These processes take quite a long time, so to feel normal you need to sleep for about eight hours.

The duration of slow-wave sleep is equal to almost three-quarters of the total time of night rest, its features are as follows:

The slow phase is characterized by a general slowdown in metabolism, a significant decrease in the brain's response to external factors, relaxation of the entire body and general lethargy. Waking up is a very difficult time and leaves unpleasant sensations for quite a long time.

In the slow phase, muscle tissue is regenerated. It is also during this phase that the immune system is “rebooted”. Thus, its normal and complete completion is a guarantee of improved well-being.

Slow sleep promotes rehabilitation and healing of the body: cell renewal occurs and the functioning of all body systems improves. REM sleep is different in that it does not have such abilities.

In fact, slow-wave sleep is divided into four components, each of which has various characteristics. Let's look at the components of slow-wave sleep.

A person who falls into a state of drowsiness, despite the decrease in physiological processes, continues to work with the brain and he thinks about and improves some of the most important ideas that he dealt with during the day. At the same time, the brain receives a sufficient amount of oxygen and works somewhat beyond its capabilities: various solutions to certain situations are searched for, and the optimal options are selected. Often it is during the dozing phase that dreams appear that have positive and pleasant results. Final solutions to some known problems came to humanity during this phase. Mendeleev, Descartes, Bohr and many other scientists admitted that the final processing of their theories occurred precisely during dozing.

Sleep spindles

This stage is also called the sigma rhythm due to the characteristic impulses observed on the encephalogram. Its distinctive feature is the almost complete blocking of consciousness, similar to that observed during anesthesia. The duration of this stage is half of the entire slow phase. It takes a very long time for the brain to prepare for deep sleep.

Notable is the fact that this activates special cells that separately block the channel of sound transmission to the brain

Delta sleep

A kind of “prelude” to the deep, it happens relatively quickly. During delta sleep, the amplitude of impulses in the brain decreases significantly, the impulses themselves become shorter - brain activity approaches its minimum.

From this stage, which begins about an hour and a half after the start of napping, we are already completely asleep. Brain activity is minimal, there is practically no reaction to any stimuli. It is almost impossible to wake up a person who is in this stage: even loud sounds, brakes and fairly strong pain are not able to interrupt it.

Dreams are present at this stage, but it is almost impossible to remember them - only fragments of images remain in memory. If it is possible to wake a person during this stage, the rise will be extremely difficult and the final restoration of the body may not occur until the next period of sleep.

Another name for this phase is paradoxical or fast wave. There is a significant activation of life processes, primarily occurring in the brain. The transition from slow-wave sleep to fast sleep occurs quickly, and serious changes occur throughout the body.

Features of the REM sleep phase include:

Increased breathing and heart rate.
Frequent arrhythmias in the heart.
Decreased muscle tone.
A significant decrease in the activity of the muscles of the neck and diaphragm.
Increased motor activity of the eyeballs with closed eyelids.
Clear memories of dreams seen during REM sleep, down to the smallest details, which is completely uncharacteristic of the slow-wave sleep phase.

With each subsequent cycle, the phases of slow and fast sleep alternate, which means that the latter has a longer and longer duration, however, its depth decreases. This happens to make it easier to get out of sleep cycles when you wake up. The prejudice that sleeping better in the morning than at night is wrong. By the third or fourth change of cycles of alternating sleep phases, it is much easier to wake a person.

The REM stage of sleep is unique in its own way. It is here that the exchange of data between consciousness and subconscious takes place, and what was thought about during dozing again enters consciousness, but now supplemented by various options that can happen.

REM sleep is usually divided into two stages: emotional and non-emotional. During the REM sleep phase, they can alternate several times, with the first phase always being slightly longer.

During REM sleep, a significant change in hormonal levels is observed. According to researchers, it is REM sleep that contributes to the daily reconfiguration of the endocrine system.

Thus, REM sleep seems to sum up all the mental activity of the brain for the whole day. Rest at this stage is necessary for a person so that he can adapt to possible options for the development of yesterday's events.

This is why interrupting this phase sometimes leads to more undesirable consequences than interrupting slow-wave sleep. In this case, we are faced with the problem of not physical, but mental fatigue, leading to possible mental disorders. There is an opinion in the scientific community that if a person is deprived of REM sleep too often, it will undermine his psyche to such an extent that it can lead to death.

For the body, the fast phase is, to some extent, a minor stressful situation. The changes taking place in it are quite radical and can lead to some undesirable consequences. For example, most heart attacks, strokes and seizures occur during REM sleep. This is due, first of all, to the fact that the relaxed cardiovascular system is subjected to a sharp and sudden load.

It is impossible to say for sure which of the sleep phases - slow or fast - is better or more important, since each of them performs its own functions. If you try to imagine the entire dream in the form of a curved line, it will look like several “dives” into deep and slow sleep, followed by “ascents” into superficial, fast sleep. The time between such ascents and descents will be approximately one and a half to two hours.

According to physiologists, this one and a half hour time period is the main biorhythm of the human body; it manifests itself not only during rest, but also during wakefulness.

In an adult, the stages of night rest are distributed approximately according to the following ratios:

drowsiness - 12%;
sleep spindles - 38%;
delta sleep - 14%;
deep delta sleep -12%;
REM sleep - 24%.

The first four belong to the phase of slow-wave sleep, the last - to fast sleep. In addition, the phases of sleep are very different and do not replace each other immediately, but over the course of an intermediate state similar to drowsiness. It lasts about 5 minutes.

During the entire sleep period, 5-6 cycles of complete changes of all stages occur. The duration of the stages may vary slightly from cycle to cycle. At the end of the last cycles, the intermediate state is the most sensitive and leads to normal awakening.

Awakening is an individual process and lasts from several tens of seconds to three minutes. At this time, the final restoration of normal organ functions and the appearance of clarity of consciousness occurs.

The main differences between NREM and REM sleep

NREM and REM sleep serve different functions. During each phase, the human body behaves differently. Often, the behavior of a sleeping person is purely individual, however, there are characteristics that are characteristic of all people, which are presented in the table.

Characteristic		Fast phase
State of the autonomic nervous system	Active work of the pituitary gland. Accelerated synthesis of most hormones	Inhibition of spinal cord reflexes. The appearance of fast brain rhythms. Increased heart rate. The emergence of a “vegetative storm”
Brain temperature	Decrease by 0.2-0.3°С	An increase of 0.2-0.4°C due to blood flow and increased metabolism
Breathing Features	Loud and deep, there is a lack of rhythm	Uneven, often rapid breathing with delays due to dreams
Eyeball movements	At the beginning of the phase - slow, at the end - almost absent	There is constant rapid movement
Dreams	Dreams are rare; if they exist, they are of a calm nature. It's hard to remember them	Bright and rich pictures and dreams, as a rule, contain a lot of active actions. Well remembered
Awakening	Associated with a depressed state, a feeling of fatigue. Severe waking up due to incomplete chemical processes during the slow phase	Waking up at the beginning of the phase causes mental fatigue. In the end - light and fast, the body wakes up rested. In this case, the state is cheerful, the mood is good

Despite the rather large difference in the nature of the phases of slow and fast sleep, both have a deep physiological, functional and biochemical relationship and are the result of the joint work of the sympathetic and parasympathetic nervous systems.

Slow sleep regulates the internal rhythms of brain areas and structures, while fast sleep promotes their synchronization and harmonious functioning.

A dream, like all beautiful things, ends sooner or later. The physical and psycho-emotional state of a person depends on at what stage of sleep the awakening occurred.

The most unpleasant thing will be to awaken in the slow phase, when it has entered the deep stage. The best time to wake up will be between the end of REM sleep and the end of the first stage of the next cycle. Standing up during the active fast phase is not recommended.

If a person has slept well, then he is full of energy, cheerful and in high spirits. This often happens at the end of the dream.

During this period, his senses are activated, and the person responds well to external irritating factors that contribute to awakening:

Light from the window.
Sounds from the street or music.
Changes in ambient temperature.

If you wake up immediately, you will feel excellent. But, if you skip this time and take a nap a little more, the body can “drag” into another slow cycle.

We often wake up shortly before the alarm clock. This is not surprising: the body itself adjusts its “internal clock” to the daily routine and the cycles occur in such a sequence that the fast phase ends at a time close to the moment the artificial clock is triggered.

If at this moment you tell yourself that such an awakening occurred ahead of schedule, then you can fall asleep again and wake up in a deep stage, ruining your entire next day.

Therefore, the best awakening is one that occurs independently, without any external factors. It doesn't matter what time it is. If the body symbolizes to us that it has had enough sleep, we cannot be deaf to such a message.

However, recently “smart alarm clocks” have begun to appear on sale, which are connected using wireless sensors to the human body. They read the body parameters and use them to determine the time of awakening - at the end of REM sleep or during the transition from it to an intermediate state.

In any case, even if waking up was easy, do not rush to jump out of bed. The body needs to be given a few minutes to adapt all its systems to the new day. The main thing in this process is not to fall asleep again, think about some idea, get ready for the new day and go ahead!

Scientists tirelessly insist that the key to good health throughout the day and health in general is sleep. Lack of sleep is fraught not only with diseases, but also with neuroses and other disorders of the nervous system. So now let’s look at why sleep is so important. Sleep norms for different ages - this will be discussed further.

A few words about healthy sleep

No one will argue with the fact that a person needs healthy sleep. So, it must be continuous and strong. Otherwise, the body does not rest completely, but partially. And all systems and organs are in an active state, which is not good for humans. What is healthy sleep?

This is a night's rest, which is enclosed within certain limits. So, it is best to go to bed at 9-10 pm. This time should be the same from day to day.
An hour before bedtime, the atmosphere in the house should be calm. Stress and excited states should be avoided.
Before going to bed, you should stop eating. The maximum you can afford is to drink a glass of kefir half an hour before going to bed.
What else is needed for sleep to be beneficial? Sleep standards - this also needs to be closely monitored. After all, if you do not rest enough hours at night, you can significantly harm your health.

Children under the first year of life

How long does it take to feel normal? The question does not have a clear answer. After all, everything depends on age. Initially, you need to understand what is the norm for a baby?

The first two months. At this time, the baby's nighttime sleep is the same as that of an adult, and averages 8-9 hours. However, at the same time, the baby also sleeps during the day, 3-4 times for a couple of hours. Generally speaking, a newborn should sleep from 15 to 18 hours in total.

Child 3-6 months. Night sleep increases, but the amount of daytime rest may decrease. In total, the baby should also stay in the arms of Morpheus for about 15-17 hours.

The baby is from six months to a year old. Gradually, the child needs less and less time for daytime sleep, and the hours of wakefulness increase. Night sleep becomes better, because the baby gets tired during the day. During the day, the baby can sleep 2-3 times for 2 hours, at night - on average 10 hours. In total, the baby should rest half the time of the day.

Preschoolers

What is the norm for hours of sleep for a child? In this case, there are also certain differences.

Children under three years old. If we talk about children under three years of age, then on average these children take 2.5-3 hours of daytime sleep, and 10-12 hours of sleep at night. It all depends on the child himself, his character, temperament, and body needs. There are babies who switch to a single daytime nap per year, and some require two - several hours each. In total, the baby should rest for 13-14 hours.

Children from 3 to 6 years old. With children of kindergarten age, things are also quite simple. If your baby goes to a preschool educational institution, he will definitely sleep there during the day for about 1.5-2 hours. On average, 10 hours are allocated for night sleep. It should be noted that, if necessary, the child can do without daytime rest. But this should not be the usual state of affairs.

Schoolchildren

Sleep is also important for schoolchildren. Sleep standards, again, vary depending on the age of the child. If we talk about children of primary school, then their night's rest should be about 10 hours. Daytime naps are no longer needed. But at first, the child may want to take a nap for an hour and you should not refuse the baby. After all, adapting to a new mode of life is not so easy. If we talk about older schoolchildren, then night sleep for such children should be 8-9 hours. It is important to remember that you need to go on a night's rest at 9-10 pm. Then it will only benefit human health, and biorhythms will not be disturbed.

Adults

What is the normal amount of sleep for an adult? So, people need to sleep on average 7-8 hours to be healthy. It all depends on the needs of the body. It is important to note that not only lack of sleep, but also too much sleep is harmful. In both cases, the result may be overwork, aggressiveness, hormonal imbalance, and problems in the functioning of the nervous system may also arise.

About sleep phases

When considering sleep and sleep norms, you also need to talk about the fact that it is important to take into account its special phases. A lot also depends on their alternation. So, in general, there are two phases of healthy sleep:

Quick sleep. At this time, the human brain is working, you can see various dreams.
Slow. This is that deep sleep when the human body relaxes and rests as much as possible.

It is also important to take into account that the slow-wave sleep phase, in turn, is also divided into several levels:

Dormant period. Here the person gradually relaxes, the brain is still very active and reacts to external stimuli.
The period of falling asleep. This stage is very important; at this time a person should be in a state of calm. People were even tortured by interrupting this period of sleep. That is, if a person is woken up during this period, over time the nervous system will become so depleted that a malfunction may occur, fraught with irreversible nervous disorders.
Deep sleep. The norm is not established here; everything depends on the work of the previous stages. This is the very tonic period when a person gets maximum quality rest, and the body gains strength and energy. At this time, it is very difficult to wake up a sleeping person.

For the body to feel great, the slow-wave sleep phase should take up approximately 75% of the time, and fast sleep - 25%. During the night, a person can enter the slow-wave sleep phase twice, which will alternate with the REM sleep phase.

During sleep, an adult alternates between 2 main phases: rapid and slow-wave sleep. At the very beginning, after falling asleep, the duration of the slow phase is long, and before waking up, the duration of slow sleep is shortened, and the duration of fast sleep is lengthened.

A healthy adult begins sleep from the 1st stage. slow sleep, lasting 5-10 minutes. Next 2nd st. lasts 20 minutes. Then follow 3-4 tbsp., continuing for another 30-45 minutes. Then the sleeper again plunges into the 2nd art. slow wave sleep, followed by the first episode of REM sleep, which takes only 5 minutes. This is one cycle.

The initial cycle lasts approximately one and a half hours. During repetitions of cycles, the share of slow-wave sleep is shortened, and the share of fast sleep is lengthened. During the last cycle, the duration of the fast cycle can reach one hour. A healthy adult experiences 5 sleep cycles during the night.

slow sleep

NREM sleep is also divided into certain stages:

The first is drowsiness with half-asleep visions. At this time, solutions to the day's problems may clearly appear in the brain.
The second is the so-called sleep spindles. At this time, consciousness turns off, but the person can be easily awakened due to increased perception thresholds.
The third is deeper sleep, in which sleep spindles are still preserved.
The fourth is the deepest sleep, which is sometimes called delta sleep. The duration of the deep sleep phase decreases from cycle to cycle.

Actually, the concept of delta sleep sometimes combines the penultimate and last stages. It is almost impossible to wake up a sleeping person during this period. This is precisely the stage in which nightmares, or nightmares, arise, but upon awakening the person does not retain memories of what happened. Normally, all 4 slow-wave stages of sleep of the 1st cycle occupy up to 80% of all sleep.

From the point of view of this phase, the body heals physically - cells and tissues are restored, self-healing of internal organs occurs. During this period, the body restores its energy costs. During REM sleep, he restores his mental and intellectual resources.

What happens during delta sleep

During delta sleep, heart rate and breathing rates decrease, and all muscles relax. As this phase deepens, the number of movements of the sleeper becomes minimal, and it becomes difficult to wake him up. If you wake up the sleeping person at this time, he will not remember his dreams.

During slow-wave sleep, according to researchers of the phenomenon, restorative metabolic processes occur in tissues aimed at compensating for the catabolism that occurs during wakefulness.

Certain facts support this hypothesis. The delta sleep stage is prolonged in some cases:

after active physical work;
during a period of rapid weight loss;
with thyrotoxicosis.

If subjects are deprived of this phase artificially (by exposure to sound, for example), then they begin to complain of physical weakness and unpleasant muscle sensations.

Delta sleep also plays an important role in memorization processes. Experiments were conducted during which subjects were asked to memorize meaningless combinations of letters before going to bed. After three hours of sleep, they were woken up and asked to repeat what they had learned before going to bed. It turned out that the more delta waves were recorded during this period of sleep, the more accurate the memories were. The results of these experiments determined that the memory deterioration that is observed with prolonged sleep disturbances and insomnia is associated specifically with problems in deep sleep.

The experimental subjects react to deprivation of deep sleep in the same way as to complete sleep deprivation: 2-3 nights with the use of stimulation reduce performance, slow down the speed of reactions, and give a feeling of fatigue.

How long should deep sleep last?

Each person has their own individual norm for how much sleep they need. There are short sleepers, medium sleepers, and long sleepers. Napoleon was a short sleeper - he slept only 4 hours. And Einstein was a long sleeper - his sleep norm was at least 10 hours. And both were very effective figures. However, if an ordinary person is forced to reduce his norm, then he will probably be negative in the morning, immediately tired and angry.

Scientists at the University of Surrey conducted an experiment in which 110 healthy adults who had never experienced sleep problems took part. On the first night, the participants spent 8 hours in bed and showed that: subjects aged 20-30 years slept 7.23 hours, 40-55 years old 6.83 hours, 66-83 years old - 6.51 hours. The same trend was observed for the time of deep sleep: 118.4 minutes in the first group, 85.3 in the middle group, 84.2 minutes in the oldest group.

The first thing that begins to suffer with a lack of delta sleep is the endocrine system. If there is a lack of deep sleep, a person does not produce growth hormone. As a result, the belly begins to grow. These people suffer from apnea syndrome: at night they experience short-term breathing stops, during which they may simply not breathe for up to 1.5 minutes. Then, out of a sense of self-preservation, the body gives the command to wake up and the person snores. This is a very dangerous condition, during which heart attacks and strokes occur much more often. When treating the syndrome, people lose weight sharply because their hormone production improves. Sleep apnea causes overwhelming daytime sleepiness, which is extremely dangerous if a person is driving at the time.

The norm for deep sleep in adults is from 30 to 70% of total sleep time. To increase its percentage you need to:

create a more efficient wake/sleep schedule (you need to go to bed and get up at the same time);
give the body physical exercise a couple of hours before bedtime (read more);
do not smoke, do not overeat, do not drink coffee, alcohol, energy drinks before bed (we compiled);
sleep in a comfortable room (ventilated, in the absence of extraneous sounds and light).

With the onset of old age, the duration of slow-wave sleep decreases. In 80-year-olds, the long sleep phase becomes 62% less than in twenty-year-olds. There are many factors that influence aging, but if the slow-wave sleep phase is also shortened, the aging process goes even faster.

How to measure your sleep

It is possible to accurately divide all 5 stages of sleep only using an encephalogram of the brain, rapid eye movements and other modern research. If you just need to even out your sleep during the week, you can use special fitness bracelets. Fitness bracelets cannot read what phase of sleep the body is currently in, but they record a person’s movements during sleep. A fitness bracelet will help divide sleep into 2 phases - a person tosses and turns (phase 1-3), sleeps motionless (phase 3-5). The information on the bracelet is displayed in the form of a fence graph. True, the main purpose of this function of fitness bracelets is a smart alarm clock, which should gently wake up a person in the REM phase of sleep.

Discovery of delta sleep peptide

In the 70s, during experiments on rabbits, a group of Swiss scientists discovered a delta sleep peptide, which, when exposed to the brain, is capable of inducing this phase. Scientists isolated it from the blood of rabbits in deep sleep. The beneficial properties of the substance are gradually being revealed to people over the course of more than 40 years of research, it:

activates stress defense mechanisms;
slows down the aging process, which is facilitated by its antioxidant properties. The life expectancy of mice during experiments with its use increased by 24%;
has anti-cancer properties: slows down the growth of tumors and suppresses metastasis;
inhibits the development of alcohol dependence;
exhibits anticonvulsant properties, helps reduce the duration of epileptic seizures;
is an excellent pain reliever.

How to increase delta sleep time

A number of experiments have been conducted studying the effect of physical activity on delta sleep. The men exercised on an exercise bike for two hours. Daytime activities had no effect on sleep duration. Evening classes had a noticeable impact:

total sleep length increased by 36 minutes;
the period of falling asleep and dozing has been shortened;
delta sleep deepened;
the cycle lengthened from one and a half to two hours.

With the introduction of additional intellectual loads (tests in the evening, solving logical problems), changes in the deep sleep phase were also recorded:

the proportion of the deepest stage increased due to sleep spindles;
2nd cycle lengthened;
an increase in the functioning of the activating systems was recorded.

Any stressful situations cause a shortening of the delta sleep phase. Delta sleep is an obligatory participant in all changes in human living conditions. Increasing its duration compensates for any load.

List of used literature:

Feinberg I. Changes in sleep cycle patterns with age // J Psychiatr Res. - 1974 - Vol. 10, no. 3-4. - P. 283-306.
Legramante J., Galante A. Sleep and hypertension: a challenge for the autonomic regulation of the cardiovascular system. // Circulation: journal. - 2005 - Vol. 112, no. 6 (9 August). - P. 786-8. - PMID 16087808.
Morrissey M., Duntley S., Anch A., Nonneman R. Active sleep and its role in the prevention of apoptosis in the developing brain. // Med Hypotheses: journal. - 2004 - Vol. 62, no. 6. - P. 876-9.

Despite the fact that the site already has an article about sleep phases, it seems right to write another article in light of the fact that new information has appeared about sleep cycles and the amount of time it takes a person to get enough sleep.

In order not to duplicate information, I refer everyone to the article Phases of Human Sleep. And in this article we will only give a brief overview of the most necessary points regarding the phases of sleep.

Another thing is sleep cycles. It is the required number of sleep cycles that gives us the opportunity to feel great in the morning after waking up. Moreover, each individual person may differ markedly from others in the number of necessary sleep cycles and, as a result, the time spent on night sleep.

In addition, I think it will be interesting to learn about what capabilities the human body has to compensate for the lack of sleep, both for the previous lack of sleep and for the future.

Let's look at all this in order.

Sleep phases

The sleep phases of any person consist of only two groups:

Non-REM sleep phase (consists of several types of sleep);
REM sleep phase.

These two sleep phases constantly alternate throughout a person’s entire sleep time, forming a single completed sleep cycle. That is, the sleep cycle consists of 1 phase of slow sleep and 1 phase of REM sleep. The duration of the sleep cycle usually ranges from 1 to 1.5 hours. Then a new cycle of similar duration begins.

Non-REM sleep stages initially occupy up to three-quarters of the total duration of the sleep cycle. But with each new cycle, the duration of the sleep phase within a given cycle changes towards reducing the duration of slow-wave sleep and increasing the rapid phase.

According to available data, somewhere after 4 o'clock in the morning, the phase of slow sleep (deep type) completely disappears, leaving only REM sleep.

What happens during non-REM and REM sleep?

The human body needs the slow phase of sleep to restore physical functions. At this time, the process of renewal of cells and internal structures occurs, energy is restored, muscles grow, and hormones are released.

During the fast phase of sleep, work occurs at the level of the mental and emotional spheres: the nervous system is restored, information is processed, memory and other structures of the body are prepared.

It turns out that each phase of sleep is extremely important for the new day of the body’s functioning.

Sleep cycles

But during one phase of sleep, the body does not have time to make all the necessary changes. Therefore, to fully restore and prepare the body for further activities during the day, several repeating cycles are needed.

Today, scientists say that the average person needs 5 repeating sleep cycles. This adds up to about 7-8 hours of sleep a night.

However, there are a fair number of people who have deviations in the number of cycles in one direction or another.

There are people who are able to fully recover in just 4 sleep cycles. They often only need 4-6 hours of sleep during the night to feel great the whole next day.

On the other hand, many people feel constantly groggy if they sleep less than 9 hours a night. Compared to other people who sleep fewer hours, such people look lazy. However, if you understand that they just need not 5, but 6 sleep cycles at night, then everything falls into place. 6 sleep cycles of 1.5 hours each give you 9 hours of sleep at night.

How much sleep do you need to get enough sleep?

To get enough sleep, each individual person needs to sleep exactly as many sleep cycles as his body requires. Usually this is 4-6 sleep cycles.

At the same time, the duration of sleep will also fluctuate considerably, because... Each person has their own sleep cycle length.

Scientists recognize 4 sleep cycles as the minimum that allows the body to more or less restore its strength. But at the same time, it is necessary to ensure that all these 4 sleep cycles are completed before 4 o’clock in the morning. This will completely complete all the body’s work to restore physical structures.

In any case, every person knows approximately how many hours of sleep he needs to feel normal. Based on this, we can conclude about the required number of sleep cycles.

Scientists have paid attention to sleep relatively recently, which is strange when you consider how much of our lives we spend sleeping. After scientific interest in sleep processes awoke, so-called sleep centers appeared at Harvard and the University of Pennsylvania, numerous studies were conducted and conclusions were drawn. In this article, you'll learn the science of sleep, why many people have trouble falling asleep, and some practical exercises for healthy sleep and more energy.

First steps in the science of sleep

The pioneer of chronobiology was the French scientist Michel Siffre, who studied biological rhythms in a harsh experiment on himself. He lived in an underground cave with a bed, a table, a chair and a telephone for calling his research team.

Michel Siffre during an experiment

His underground home was lit by just one light bulb with a soft glow. From food - frozen foods, several liters of water. There were no clocks, no calendars and no way to know what time it was on the surface, day or night there. And so he lived alone for several months.

A few days after descending into the cave, Siffre's biological clock began to work. He later recalled how he felt during the experiment:

My sleep was wonderful. My body chose when to sleep and when to eat. This is very important. My sleep-wake cycle did not last 24 hours, like people on the surface of the earth, but a little longer - about 24 hours and 30 minutes.

Thus, despite the absence of sunlight and any knowledge of whether it was day or night, his circadian rhythms continued to work.

After this experiment, many scientists became interested in sleep research. New research has helped to understand how much sleep you need, why you need to do it, and how you can make up for lack of sleep.

How much sleep do you need

How much sleep do you really need? To answer this question, let's turn to an experiment by scientists from the University of Pennsylvania and Washington State University.

The researchers collected 48 healthy men and women who were accustomed to sleeping 7–8 hours a day. The participants were then divided into four groups.

People from the first group had to survive without sleep for three days, from the second group they had to sleep 4 hours a day. Participants from the third group were allowed to sleep 6 hours a day, and from the fourth - 8 hours.

Three groups that slept 4, 6 and 8 hours a day were required to maintain this regimen for two weeks. During the experiment, scientists monitored the physical health and behavior of the participants.

As a result, the group of participants who slept 8 hours a day did not experience any impairments throughout the experiment - decreased cognitive function, worsening reactions or memory lapses. At the same time, all indicators gradually worsened in people who slept 6 and 4 hours a day.

The group with 4 hours of sleep performed worse, although not significantly, than the group with 6 hours. Overall, two significant conclusions were drawn from the experiment.

First, lack of sleep tends to accumulate. In other words, lack of sleep has a neurobiological cost that only increases over time.

After one week of the experiment, 25% of participants who slept 6 hours a day periodically fell asleep at different times during the day. After two weeks, people in this group showed the same results as if they had spent two days without sleep at all.

Lack of sleep gradually accumulates.

The second finding is equally important: participants did not notice a decline in their performance. The participants themselves believed that their performance worsened over several days and then remained the same. In fact, their scores continued to decline throughout the experiment.

We don't notice a decline in cognitive function when we don't get enough sleep.

It turns out that we assess our condition very poorly and cannot accurately determine how well our cognitive functions are working. Especially in today's environment of constant social activity, caffeine and many other factors that help you feel fresh and alert, even if in reality this is far from the case.

The cost of lack of sleep

The irony is that many of us suffer from lack of sleep while trying to earn more. But no matter how many extra hours you spend working instead of getting enough sleep, it won't increase your productivity much. Your attention, memory and other functions deteriorate, and you perform all tasks more slowly and poorly.

Research has found that decreased productivity due to lack of sleep costs US businesses a huge amount. On average, $100 billion is lost per year.

Here's what George Belenki, director of the Sleep and Performance Research Center at the University of Washington, had to say about it:

If your job involves mental activity, you pay in productivity for lack of sleep.

After this, a completely logical question arises: how much time do you need to sleep so as not to accumulate fatigue and decrease productivity?

Based on research data, we can say that this time is from 7 to 7.5 hours. Overall, experts agreed that 95% of adults need 7 to 9 hours of sleep per night to be productive.

Most adults benefit from 8 hours of sleep per night, and even more for children, teenagers and older people.

How sleep works: sleep and wake cycles

The quality of your sleep is determined by a process called the sleep-wake cycle.

There are two important points in this cycle:

Non-REM sleep (also known as deep sleep).
REM sleep phase (REM phase, rapid eye movement phase).

During non-REM sleep, the body relaxes, breathing becomes calmer, blood pressure drops, and the brain becomes less sensitive to external stimuli, making it more difficult to wake up.

This phase is of great importance for the renewal and restoration of the body. During the slow phase of sleep, growth hormones are produced in the pineal gland, which ensure tissue growth and muscle repair.

Researchers also suggest that the immune system is restored during non-REM sleep. So slow-wave sleep is especially important if you exercise. Some professional athletes, such as Roger Federer or LeBron James, slept 11–12 hours a day.

Another example of the effect of sleep on physical performance is a study conducted on basketball players at Stanford University. During the study, players slept at least 10 hours a night (as opposed to the 8 hours they were used to).

The experiment lasted five weeks, during which the researchers assessed the players' speed and accuracy compared to their usual performance.

It turned out that just two extra hours of sleep increased the number of successful throws by 9% and reduced the time for the 80-meter sprint by 0.6 seconds. So, if you have heavy physical activity, slow-wave sleep can help you recover.

REM sleep is as important to the mind as non-REM sleep is to the body. The brain is quiet most of the time when you sleep, but when REM sleep occurs, it becomes more active. This is the phase during which you dream and your brain redistributes information.

During REM, the brain clears out unnecessary information and improves memory by linking experiences from the past 24 hours with previous experiences, facilitating learning and triggering the growth of neural connections.

At this time, the body temperature rises, blood pressure rises, and the heart beats faster. In addition to this, the body moves. In general, REM sleep occurs three to five times per night for short periods of time.

A person cannot function normally without both stages of sleep. Sleep deprivation affects your health: your immune system weakens, your consciousness becomes “foggy,” your risk of infectious diseases increases, your blood pressure and the risk of heart disease increase. In addition, sleep deprivation threatens mental illness and shortens life expectancy.

The slow phase of sleep helps restore physical health, the fast phase - mental capabilities.

However, despite the enormous importance of sleep for the body, the quality and duration of sleep changes throughout life.

Age-related changes in sleep

Based on research from Harvard Medical School, it can be said that as people age, it becomes increasingly difficult for people to fall asleep. This phenomenon is called sleep latency. And sleep efficiency - the percentage of time you spend in bed asleep - also decreases.

On average, 80-year-old people have 62% less duration of sleep than 20-year-olds. There are many factors that influence tissue aging, and if the slow-wave sleep phase is reduced, the aging process occurs even faster.

Healthy sleep is your best weapon against rapid aging.

How to recover from lack of sleep

Most adults need 8 hours of sleep to keep their body functioning at its best. Since older people have trouble sleeping, they can make up for the lack of sleep at night by taking a nap during the day.

In any case, if you realize that you need to take a nap, it is better to do it once in the middle of the day than to periodically fall asleep during the day and evening.

In general, the body recovers well from short-term lack of sleep. For example, if you had a rough night and managed to get 2–4 hours of sleep, the next night 9–10 hours of sleep will completely restore your body.

Your body will simply spend more time in REM and non-REM sleep to make up for the lack of sleep from the previous night.

There is no need to plan how much time your body will spend in REM and NREM sleep. It knows better how much sleep and what kind is needed for recovery, so you won’t be able to control this process.

And remember that sleep cannot be replaced by anything. If you have to stay awake longer today, make sure you sleep longer than usual the next night.

Circadian rhythms

How are your sleep-wake cycles organized?

Using circadian rhythms. These are biological cycles of different processes that occur within 24 hours.

Here are some key points about the 24-hour cycle:

6:00 - Cortisol levels rise to force your body to wake up;

7:00 - melatonin production stops;

9:00 - peak production of sexual hormone;

10:00 - peak mental activity;

14:30 - the best level of coordination of movements;

15:30 - time of best reaction;

17:00 - better functioning of the cardiovascular system and muscle elasticity;

19:00 - highest blood pressure and highest body temperature;

21:00 - melatonin begins to be produced to prepare the body for sleep;

22:00 - the digestive system calms down as the body prepares for sleep;

2:00 - deepest sleep;

Of course, these are only approximate rhythms, since they are individual for each person and depend not only on daylight, but also on habits and other factors.

In general, circadian rhythms are influenced by three main factors: light, time, and melatonin.

Light

Light is one of the most significant factors setting the circadian rhythm. Staying in bright light for about 30 minutes can reset your rhythms, no matter what time it is.

Basically, when the sun rises and light hits your closed eyes, it signals the start of a new cycle.

Time

The time of day, your daily schedule, and the order in which you tend to perform different tasks all affect your sleep and wake cycles.

Melatonin

It is a hormone that causes sleepiness and controls body temperature. Melatonin production depends on a daily, predictable rhythm. Its amount increases in the dark and decreases when it becomes light.

How to sleep better

Here are a few rules for falling asleep quickly and sound sleep.

Avoid caffeine

If you have trouble sleeping, it's best to eliminate caffeine from your diet altogether. But if you can't get going in the morning without a cup of coffee, at least don't drink it after lunch.

Quit smoking

In the experience of many people who are quitting or have already quit smoking, cigarettes have a bad effect on sleep. After you quit smoking, it will be easier to fall asleep and the number of awakenings at night will decrease.

Use the bedroom only for sleep and sex

Remove the TV from the bedroom, do not bring a laptop or tablet. The ideal sleeping environment is a dark, cool and quiet bedroom, so try to make it that way.

Exercises

Physical activity helps your body and brain switch off at night. This is especially true for older people. It has been proven that mobile, active older people sleep much better. However, at least three hours should pass between classes and sleep so that the brain and body have time to calm down and prepare for sleep.

Temperature

Most people sleep better in a cool room. The ideal temperature in the bedroom is 18–21 °C.

Sounds

A quiet room is ideal for a great night's sleep. But if you find it difficult to fall asleep in complete silence, you can turn on white noise.

No alcohol

A small (or very large) amount of alcohol can help you fall asleep, but the quality of such sleep leaves much to be desired. During such sleep, the REM phase is shortened, so that you do not have proper rest, even if you slept all night.

How to get ready for bed

Here's what you need to do to avoid insomnia.

Set a daily schedule

Our body loves systems. Essentially, the circadian rhythm is your daily routine on a biological level. Go to sleep and wake up at the same time every day.

Get into the habit of turning off all electronics an hour or two before bed. Light from a computer, TV, or smartphone delays the production of melatonin, which helps the body prepare for sleep.

Additionally, working before bed increases brain activity and can increase stress levels, which can have a negative impact on sleep. Instead of checking work email, read a paper book. This is a great way to get away from the screen and learn something interesting and useful.

Use relaxation techniques

Researchers say that strong emotional experiences and stress are to blame for 50% of insomnia cases. Find a way to reduce stress and you'll find it much easier to fall asleep.

Proven methods include journaling, breathing exercises, meditation, and exercise.

Don't miss the opportunity to take a nap

Afternoon naps help replenish sleep cycles. This will be especially useful for those who cannot get a good night's sleep.

How to be more energetic in the morning

Drink a glass of water in the morning

Your body has spent 6 to 8 hours without water. Feeling sleepy in the morning (if you've had enough sleep, of course) can be caused by a lack of moisture. So a glass of cool water may well refresh you.

Start your day in sunshine

Sunlight in the morning is especially important for your circadian rhythm. Light awakens your brain and body, so during the sunny summer months you don't even need your morning coffee. The main thing is to stay in the light in the morning.

Conclusion

So, the main idea of this article is that nothing can replace sleep. If you quite consciously expose yourself to deprivation, you do not allow your brain to work at its full potential and your body to recover.

Lack of sleep is the barrier between you, health and productivity. So get more sleep.