How to harden up? Start in summer or autumn. Boost your immunity

Hardening always evokes the question of whether it will make our immune system more resilient. To begin with, we need to explain how it all works.

Body temperature

The human body tries to maintain a steady temperature, around 36.5 °C. The thermoregulatory centre helps it to do this. It is located in a part of the brain called the hypothalamus.

Humans have the lowest temperature in the morning and the highest in the evening.

Temperature changes are recorded by the temperature-sensing nerve endings - the thermoreceptors. They are located in the skin. The skin also acts as a thermal insulator, especially the fat layer.

How the body perceives heat and cold

It uses heat and cold sensors - thermoreceptors. In humans, they are found in the skin, in the hypothalamus and in some organs and blood vessels.

Receptors for sensing heat are deeper in the skin than those for sensing cold, and there are fewer of them. It follows that the body is more sensitive to cold than to heat.

Cold receptors respond to temperatures between 10 and 38 °C and heat receptors between 30 and 45 °C.

There are separate cold and heat receptors on the skin. There are 4-10 times more cold receptors. The most thermoreceptors in humans are located around the

• eyes
• nose
• lips
• ears

On the torso, on the other hand, there are relatively few.

When a change in temperature is detected on the surface of the skin, the person's nervous system reacts. There is a change in behaviour and reaction of the organism. The person tries to hide in warmth or cold.

The following table shows the body's reactions

The heat and cold receptors are located under the skin. Therefore, they respond to the temperature of the subcutaneous tissue and not to the outside temperature.

Adaptation of the body is present at a skin temperature range of 20 to 40 °C. Below and above this temperature range, there is no adaptation. This means that the sensory stimuli caused by heat gradually diminish. Above 45 °C, temperature stimuli cause pain, because by then tissue damage has already occurred.

Water dissipates heat 27 times faster than air.

If the body wants to maintain thermal equilibrium at low outside temperatures, it must increase its heat production and reduce its heat output. By constricting blood vessels, it prevents heat loss to the outside environment. It produces its own heat by muscle shivering.

Thermoregulation

The body's temperature depends on the intake, production and expenditure of heat. The balance between these is provided by thermoregulation. Its centre is the hypothalamus. Here, information from the thermoreceptors - the heat and cold sensors - is evaluated.

The body's core is warm-blooded. When there are large changes in ambient temperature, its temperature hardly changes at all. This is true under certain conditions, however, as long as thermoregulation is not disturbed.

The outer parts of the body (skin, limbs) are cold. They partly try to adjust their temperature to the environment. This prevents high heat loss.

Thermal comfort is a state of the organism where it does not have to engage the thermoregulatory mechanism due to a favourable ambient temperature. This temperature is approximately 20-21 °C when clothed or 28-30 °C when naked.

Heat production in the body

In the body, heat is produced during metabolic processes and muscular work. Its production involves:

• the main metabolism of all cells
• the thermogenic effect of food
• increased metabolism by the action of hormones
• increased metabolism by muscle work, muscle tremors or digestion
• thermogenesis in brown fat

Thermogenesis is the increase of heat production in the body when exposed to cold. Brown adipose tissue is important for thermoregulation especially in newborns. It also partially fulfills its function in adulthood.

About 18% of the heat is generated in the muscles when they are at rest. When they are working, this can rise to 90%. The rest of the heat is generated by the brain and other tissues. When body temperature falls below 35.5 °C, muscle tremors occur. The body then tries to generate heat.

The body's heat output

Depends on the thermal insulation properties of the individual tissues of the body. In the human body, blood is an excellent conductor of heat. Fat tissue is an insulator.

Thermal insulation

The best insulators to protect the body from heat loss are the skin, subcutaneous tissue and fat. Heat loss at the periphery of the body is also prevented by the so-called counter-current mechanism. This works by the heated blood flowing from the core of the body transferring its heat to the cool blood returning from the periphery.

Normally dressed people cut their heat loss by about half. Wet clothing increases heat loss by up to 20 times.

Heat loss is divided into direct and indirect.

Direct heat loss

Radiation (emanation, radiation) takes place by means of electromagnetic waves. If the air temperature is lower than the body temperature, about 65% of the heat is dissipated. This is under the condition that the body is not exposed to extreme conditions. These are mainly high temperature, high humidity or high air velocity.

Conduction is the transfer of heat from a body at a higher temperature to a body at a lower temperature. It removes about 2% of the heat. Under normal thermal conditions, a naked person in a closed room loses about 15% of the heat energy. Air is therefore a fairly good insulator under such conditions. However, the situation changes if the surrounding environment is fast moving air or water.

Convection (flow) is closely related to conduction, i.e. conduction. In this heat loss, unlike radiation and conduction, there is also a transfer of substance, not just energy. Primarily, heat is sold to the substance by conduction, and dissipated to the surroundings by its flow. About 15% of the heat energy is dissipated in this process.

The effects of conduction and convection are most pronounced during extreme weather conditions. The human body will tolerate freezing temperatures with no wind and low humidity better than temperatures slightly above freezing with high humidity and high winds.

Indirect heat loss

evaporation is the conversion of fluids from the surface of the body, i.e. sweat, to a gaseous state. About 30% of the heat is removed. Evaporation of water from the body occurs during respiration (breathing) and sweating.

There is a distinction between marked and unmarked sweating.

It takes place with the help of the sweat glands. It is the basic mechanism of heat dissipation if the high ambient temperature does not allow other mechanisms of heat loss. It is regulated by the organism and influenced by the environment. Under extreme conditions, water loss can be up to 1.5 litres per hour.

The less voluminous, insignificant perspiration is caused by the spontaneous diffusion of water through the skin, a process that is almost unregulated by the human body. The sweat glands are not involved at all. It is mainly due to environmental conditions. The water loss is about 660 ml per day.

The reduction in body temperature

When the body temperature rises, the organism tries to lower it. It uses various regulatory mechanisms to do so. These increase the outflow of heat to the environment:

• vasodilation - dilation of blood vessels, which increases heat transfer to the skin from the body core by up to eight times
• volumetric sweating - activated from a body temperature of 37 °C
• limitation of heat production by the body

Increase in body temperature

When the body temperature is lowered, the body uses mechanisms that try to raise it. Thus, they reduce the outflow of heat to the surrounding environment:

• vasoconstriction - constriction of blood vessels that mobilizes at body temperatures of 36.8 °C or less
• an increase in heat production
• thermogenesis - heat production by muscle shivering
• increase in metabolism
• the formation of so-called 'goose bumps' - a remnant from animals that increase the insulating properties of their fur
• feeling of hunger

The effect of extreme temperatures on the human body

The human regulatory mechanism has the ability to maintain a constant core body temperature within the range of 12-54 °C of the external environment. Outside these values, so-called free regulation is very important. It consists, for example, of seeking shelter from the effects of extreme temperatures, clothing or active exercise.

High temperatures

Excessive perspiration occurs at high ambient temperatures and their effect on humans. There is an increased production of aldosterone.

Aldosterone is a hormone that regulates the levels of sodium and potassium in the human body. It retains sodium and increases the excretion of potassium. This affects the properties of the extracellular fluid.

Overproduction of this hormone prevents high ion losses during sweating and increased blood volume.

Older people often have a lower body temperature. This is because of lower activity and cardiovascular capacity. At high ambient temperature, the risk of vasodilation - dilation of peripheral blood vessels - increases. Cardiac output and dehydration are impaired. This can lead to collapse.

Interesting information:
Summer and hot weather bring health risks

Cold temperatures

When returning from a lower temperature environment to a normal environment, the body reacts by spontaneously raising its body temperature. It usually remains intact. Its resistance to low ambient temperatures is therefore greater.

However, if the core temperature drops below 28 °C, spontaneous return is almost impossible. However, when the core is warmed up, it returns to its normal state.

Under certain circumstances, a person can tolerate a drop in temperature down to 21 °C. However, this is used in medicine and not in everyday life.

However, when the core temperature drops to 24 °C, for example by being in ice water, cardiac arrest and, without help, death occur.

Newborn babies are more prone to hypothermia because they have a relatively large body surface in proportion to their core body mass. They also have a thin layer of subcutaneous fat and a thermoregulation system that is not yet functioning properly.

Hardening - how to get started

Will hardening make us healthier? It may not cure us of disease, but it will boost our immune system. It will make it more resilient.

It affects not only our physical side but also our mental side. It strengthens physical fitness and mental willpower.

It is up to us which form we choose to take. But it is not necessary to overdo it to begin with.

The difference between recreational and sports hardening is shown in the table below

Can everyone harden themselves?

From a technical point of view, it is not that simple. Hardening is a long-term process and the body is exposed to extremely low temperatures.

Any healthy person between the ages of 17 and 40 can start winter swimming. They must, of course, undergo a medical examination. Younger people are only exempted by a sports doctor and can only start after the age of 40 after a thorough medical examination with a doctor's recommendation.

The basics of hardening

The basic principle is to take cold showers at home. Start with lukewarm water and gradually add cold water.

The evening shower is, of course, permitted, but it does not replace the morning shower. It only supplements it. The morning shower should be longer than the evening shower. As a rule, it should take twice as long.

In winter, showers should last 1-3 minutes and in summer 3-5 minutes.

Mental well-being should be sought when showering. It strengthens the willpower. One should keep moving. The head should be covered with a bathing cap to avoid getting the hair wet.

After showering, you should dry yourself properly with a dry towel and warm up by moving around. Therefore, you should do a short exercise. Have breakfast after your shower.

Taking a shower under stress has a bad effect on mental well-being, so it is not recommended to take a shower when you are pressed for time.

It is only after at least 2 years of regular hardening that one becomes a true hardener.

Hardening and its effects on human health

Hardening in the open air can be started after at least six months of home hardening. Various sports activities and, later, swimming are carried out in all weathers.

It starts in summer, continues in autumn and also in winter. Then constant movement is needed. After about 2 years of such activity, the organism becomes more resistant to various diseases and colds. If they do occur, their course will be milder. Hardening increases the organism's threshold of sensitivity to various viruses and bacteria and makes it easier to cope with them.

Exposing the body to low temperatures causes the blood vessels to contract and, conversely, to stretch when warmed up. This makes them more elastic and delays their ageing.

After swimming in cold water, endorphins - the hormones of happiness - are released into the body. This results in improved mood and stress relief.

If you want to know more about this, read the article on stress relief.

Biorhythm and diet

Regular and sufficient sleep should be maintained. Go to bed at the same time. Cover yourself with only a light blanket while sleeping. Keep the window open at least until the end of autumn.

The temperature should be 12 °C in the bedroom and 20 °C in the living room.

Clothes should be comfortable and airy even during the winter months. Constant exercise is essential. It is not true that if someone is hardy they will never get cold. If they do not move enough, this can happen even to the hardy.

It is not a good idea to cover your nose and mouth with a scarf in winter. When you breathe out, bacteria get trapped on them. These are then re-inhaled into the body.

Hardening off is actually exposing yourself to low temperatures. Therefore, there is an increased expenditure of calories. Therefore, the diet should be appropriate to this expenditure of energy.

The body needs 400 calories to maintain a body temperature of 4 °C in cold water. This leads to the misconception that this is a way to lose weight quickly. However, during hypothermia the body's fat loss slows down. The body tries to maintain an insulating layer.

For this reason, a diet rich in fat should be avoided after hardening. It doesn't matter what form it takes.

The intake of fluids and minerals is important. Vitamins are obtained by eating fruit and vegetables. Particularly important are those from groups C, A, B, E and D. A hardy person does not have to be a vegetarian or vegan, but a healthy diet is necessary.

Sports hardening

Should not start at all without a medical examination. One should take 1-2 years of shower hardening before moving on to sports hardening. Swimming in cold rivers and bodies of water.

Start in summer, every day and in all weather. Swim in rivers, lakes or uncovered pools.

In the warmer months, when the water is warmer, you need to focus on swimming technique. It is also important to train swimming endurance by swimming distances of 1-2 kilometres or more.

This cannot be trained in cold water. This is when the differences between good and less fit swimmers become blurred. In cold water, the back and leg muscles stiffen. This is when even a good swimmer struggles to swim fast and well.

Due to mental endurance, it is recommended to swim in a group of swimmers.

The table below shows the length of time spent in the water depending on the water temperature

If the water temperature is less than 12 °C, it is not good to swim more than 2-3 times a week. The body needs more time to recover after swimming. In such cases, one must not overestimate one's own strength.

During the big stroke, when endorphins are released, the swimmer feels physically well. This often leads to misjudgement and overestimation of one's own abilities. Therefore, in hardy competitions, when the water temperature is below 10 °C, swimming is limited to 22 minutes.

In open water or in rivers, the swimmer must swim along the bank. If the time limit is reached, the swimmer can get out of the water at any time. In rivers, the swimmer is also exposed to strong water currents. He needs more strength to swim. Therefore, only top swimmers should really swim in rivers.

The flowing water also cools the body more quickly by encircling the body, and it becomes hypothermic much sooner.

Warm up

You can't do without a warm-up in any sport. It's even more important in hardening off. The aim is to warm up the body so that its temperature adapts to its surroundings. This can be done by a short run or by exercising. Of course, the clothes you wear when you go in the water are the ones you'll be wearing.

The body is to be warmed by movement even after the swim is over. In the cold months it is not advisable to go straight from the water to a heated room to warm up. It is also out of the question to take a shower in warm water. In such cases there is a great danger of collapse.

You should dry yourself thoroughly and dress slowly and with constant movement. It is advisable to replenish fluids with warm tea. This works from the inside. It warms the blood in the vessels, which is then transported throughout the body.

How to give the body energy before and after swimming?

It is a misconception that one should eat a proper meal before such an exercise. Nothing should be eaten less than 2 hours before. Warm soup is best. Nothing in the form of hard-to-digest proteins (meat) is recommended. These do not give the body energy. On the contrary, they take it away by digesting it.

Alcoholic 'warm-up' drinks are absolutely out of the question. Alcohol dilates the blood vessels in the body. This means that heat is lost from the body more quickly and the person becomes hypothermic more quickly. Its psychostimulating effects are also undesirable in this case. Self-esteem rises, sound judgement is lost and the person is more prone to overestimate his or her own abilities.

After the swim, the body needs to be replenished slowly. The body needs to be warmed up and replenished with warm tea. The body uses a lot of energy to do this. If food were consumed immediately, it would become even more stressed. It is necessary to wait until the muscle tremors have subsided.

Throughout the year, but especially in winter and with the arrival of spring, vitamins should be supplied to the body in increased amounts. Preferably by eating fresh fruit and vegetables.

How should I dress for hardening?

Swimwear is the clothing of every swimmer. A swimming cap should also be worn. In summer, it protects against the scorching sun. During long-distance swimming, heatstroke could occur without it. In winter, it protects against heat loss. A lot of heat is transferred from the body to the environment through the head. This is due to its rich vascular supply. It is also not recommended to immerse the head in water in winter.

Lightweight swimming shoes are suitable as footwear to protect the feet from dirt on the bottom of the water.

Hardening during illness

In principle, it is not recommended to continue hardening off during illness.

It is necessary to wait for a full recovery. After that, a week's rest is necessary. Only then can moderate training be started. However, during this time, it should not be in the usual doses, but in smaller doses.

In more serious conditions, hardening should be interrupted for longer or stopped altogether.

What are the risks to the body during hardening?

During hardening, the body is exposed to very low temperatures. This brings with it certain risks.

Frostbite

Frostbite is an injury to a part of the body caused by cold. The damage to the tissue is greater when the body is slowly cooled down. Repeated frostbite to the affected parts after the frostbite has been warmed up is equally dangerous.

The formation of frostbite does not depend on temperatures below zero. It is quite sufficient if the body is exposed to rain, cold or wind.

Symptoms are varied. Most often, a pinching, cold or tingling sensation is observed in the affected area. Loss of sensation is often present. A burning or shooting pain is present on warming.

Primarily the peripheral parts of the body are affected where there is less blood supply or where they are most exposed to the cold, especially the ears, cheeks, nose, fingers and toes.

Frostbite is divided into 4 stages, but has no effect on its treatment.

4 degrees of frostbite in the table

In addition to these symptoms, tissue necrosis, gangrene, may occur.

Lay first aid is uncomplicated, but certain principles must be followed.

1. Primary treatment should be life-threatening conditions, if present. These include disturbances of consciousness, breathing or circulation.
2. Remove wet clothing and wrap the casualty in a warm blanket, for example.
3. To reduce swelling of the affected part, it should be held in an elevated position.
4. It is necessary to start warming the affected part, but not if there is a risk of refreezing.
5. The nose or ears should be covered with a cloth or bandage, the hands and fingers can be placed under the arms.
6. Serve warmed soft drinks with honey or chocolate.
7. Stay warm with the sufferer if possible.

It is not advisable to massage or rub the site with a cloth if the impairment is of a greater degree. There is a risk of skin damage and infection entering the body. It is also not recommended to heat the site of the impairment with dry heat for any impairment. For example, using a hair dryer, heater, etc.

The affected person should be transported to a medical facility.

Hypothermia

This is caused by the body being exposed to a cold environment. The core body temperature falls below 35 °C.

The body loses heat in various ways, but mostly by radiation. The environment has a major influence. In cold water, heat loss increases 27-fold.

Hypothermia(hypothermia) affects all organs in the body. The cardiovascular system and the central nervous system are most affected. This includes the brain.

According to the symptoms, hypothermia is divided into 3 stages.

Mild hypothermia. In mild hypothermia, the core temperature drops to 35-32 °C. Up to 34 °C, there is tremor in the extremities. Below 34 °C, there are changes in thinking and difficulty in speaking. Breathing becomes more rapid. At a core temperature of 33 °C, there is incoordination of movements and mental retardation.

Moderate hypothermia. Core temperature drops to 32-30°C. Consciousness is impaired. Heat is no longer generated by shivering. Risk of cardiac arrhythmias increases. Heart function decreases.

Severe hypothermia. Below 30°C core temperature. Unconsciousness develops. The victim is unresponsive to any stimuli. Respiration and cardiac arrest occur.

First aid must be rapid and, depending on the condition, the immediate life threat must be dealt with first. Unconsciousness or cessation of breathing.

The hypothermic patient should be moved slowly and as little as possible. Wet clothing should be removed and wrapped in something dry. The ambient temperature should be raised if possible. Warm compresses should be placed under the arm and on the abdomen as soon as possible. If there is no other option, active warming by direct body contact may be used.

If the hypothermia is mild, there is no risk of cardiac arrhythmias. Then the casualty may be warmed by any means. Alcohol and caffeine-free drinks may be given. Sweet foods are consumed. Grape sugar is ideal. Rapid transport to a medical facility should be arranged, or assistance summoned.