Post it on the forum in this folder (Editing and Writing Topics). I will do what I can.
- For Teachers
I would really appreciate if some native speaker could proofread this text. It is an article that my friend (doctor) wrote. He is supposed to present it on a medical conference next week. English is not his first language, so he asked me to ask some native speaker to correct it. Could anyone help me please ?
Post it on the forum in this folder (Editing and Writing Topics). I will do what I can.
I love this site becuase it proofreads for ya...<3
I had a go at this but have had problems getting it back.
Here's the first few paragraphs with my suggestions:
Physical activity in a cold environment
Institute of Sports Medicine, Medical Faculty Plzen, Charles University Prague,
Cold stress is any environmental condition that causes a loss of body heat leading to homeostasis. Two major cold stressors are cold air and water.
Man is a typical tropical animal. This is confirmed also due to the critical temperature. Critical temperature is the lowest ambient temperature at which a nude man sustains his body temperature at rest without raising his metabolic rate. The greater the thermal gradient between the skin and a cold environment, the bigger are the heat losses.
Critical temperature in humans for air (Tac) is 22 - 27 °C, for water (Twc) 32 - 35 °C. Cold-adapted people have lower values.
Survival time for shipwrecked men in different water temperatures (Tw) based on reported experience from the 2nd World War (Thauer 1965) indicates that the corresponding time for 14°C is 8 hours, despite the fact that cross channel swimmers can be swimming in this Tw for as long as 13-20 hours. The explanation for this consists in the different physical and mental condition of swimmers and in their adaptation to cold.
Is it better to swim or not in order to maintain body heat?
The advantage of swimming consists in the heat production. However swimming also has disadvantages. It produces vasodilatation in the body surface area and in active muscles, and the cold water streams along the body. Hence the body cooling is greater.
In what Tw is it better to swim? In most people Tw 18 °C forms the borderline. Over that, it is better to swim; below that it is better to remain at rest.
And the next few: In the picture you can see body surface areas with the greatest heat losses. These are mainly lateral chest areas, inguinal areas and the head. So the best position for a man in cold water is HELP (Heat Escape Lessening Posture) or huddling posture.
According to our observations, the rectal temperature (Tr) in winter swimmers during 20 minutes of swimming in Tw 4 °C decreased on average to 34.8 °C.
During the same period swimming in Tw 25 °C, Tr increased to 38.3 °C. Both systolic and diastolic blood pressures (BP) increased during swimming in cold water.
After swimming, hematocrit increased and plasma volume decreased (by 8%).
Protection against heat losses is possible in two ways: Extension of the isolative ability of the body surface and Thermogenesis.
Man intensifies body insulation through his actions; such as reduction of the body surface with the help of the shrink [I can’t interpret this – does he mean “shiver”] and selection of suitable clothing.
At work in a cold environment it is important not to clothe oneself too warmly. This can lead to overheating with perspiration. Due to perspiration-soaked slothing, the body temperature is reduced and during long-term endurance activity shivering can occur.
Body size and composition
Tall, muscular individuals have a small surface area to body mass ratio; hence they are less susceptible to hypothermia. Small children have a large surface area to mass ratio; hence their heat output is greater.
Women have on average more body fat than men which is an advantage in a cold environment. But in similar body fat mass and size, there is only a little difference between genders.
A. Extension of the isolative ability of the body surface
The first reaction to cold stimulus is vasoconstriction both in the skin and subcutaneous tissue and in inactive muscles. Vasoconstriction in an extreme cold is often changed by vasodilatation. It has been observed in Eskimos, Norwegian fishermen and in the Ama. Vasodilatation has its local benefits, which consist in greater resistance against frostbite and in preserving an important hand function in the cold.
During the long-term cold adaptation, higher subcutaneous fat thickness occurs. Subcutaneous fat is an excellent source of isolation for its small thermal conductivity and relatively low vascularization.1 mm of the adipose tissue allows cold-adapted man to endure about 1 - 2 °C cooler air.
and the rest:
B. Increased heat production – thermogenesis is possible in 2 ways:
- muscle activity and shivering
- increasing of the metabolic heat production – nonshivering thermogenesis
These mechanisms are not equally effective from the aspect of thermal regulation. Muscle activity and shivering increase the body surface perfusion, hence they reduce body surface isolation and greater heat losses occur. It concerns mainly a naked man in the extreme cold.
The most effective form is the nonshivering thermogenesis (NT).
NT is induced due to catecholamines, especially norepinephrine (NE). NT is well known in cold-adapted animals. It takes place in brown adipose tissue (BAT). In humans it was proved for a certainty in new-born children only
Is NST possible also in adults?
NT need not be located in BAT only. (Shepard 85). A greater metabolic response occurs in humans when epinephrine (E) was infused (Simonsen92). Localization of NT in man is probably in muscles and in white adipose tissue because the metabolism is increased by epinephrine there.
Air temperature alone is not a valid indicator of thermal stress. A cold wind increases the rate of heat loss significantly, and the more humid the air, the greater the stress.
Equivalent temperatures at different wind speeds according to Wilmore and Costill (1999) show us that -7 °C at 65 km/h wind speed is equivalent to -29 °C in calm air.
Cold and physical activity
Cooling a muscle causes its function to worsen. Both muscle shortening velocity and muscle power decrease. The muscle fatigue arises earlier. Significant changes appear after the muscle temperature decreases from 35°C to 25 °C. If clothing insulation and exercise metabolism are sufficient to maintain the athlete‘s body temperature, exercise performance may be unimpaired. After the fatigue sets in and muscle activity slows, body heat production gradually decreases. Endurance activities in the cold can expose the participants to such conditions. In hypothermia, exercise activity declines and this reduces metabolic heat production. It causes the individual to become more fatigued, whereby a potentially dangerous situation can occur.
Cold is a stress stimulus which activates the sympathetic nervous system. This triggers a marked catecholamines release. Norepinephrine (NE) increases the blood pressure, free fatty acids (FFA) mobilization, and leucocytosis and spleen lymphocytes mobilization. Deiodination tissue activity rises. The pituitary – adrenal axis is also activated.
For the development of the cold adaptation, thyroid hormones are necessary.
Catecholamines in cold and exercise cause reduction of the blood flow in the stomach, intestines, the skin and kidneys. Both the plasma flow rate in the kidneys and glomerular filtration rate decrease, while proteinuria increases.
Blood glucose plays an important role in cold tolerance and exercise endurance. Hypoglycaemia suppresses shivering and significantly reduces body temperature (Tr). Hence during endurance activities in cold environment the refreshment through food intake plays an important role.
The following pictures show us changes in earlier mentioned parameters during and after 20 minutes of swimming in ice cold water.
Reactive types of the cold acclimation:
- Metabolic consists in increasing heat production.
- Isolative. Heat production is constant. The insulation increases.
- Hypothermic. Body temperature declines. Organism is adapted to lower body temperature.
Reaction and adaptation to cold in seniors
- Tr in the cold depends mainly on the subcutaneous adipose tissue.
- By approximately identical adipose tissue Tr declines more in seniors.
- Both systolic (BPs) and diastolic (BPd) blood pressure increase in seniors till double in the cold.
- Acclimation to cold in seniors develops slowly.
- Cold and heat perception decreases in seniors. Young people recognize the difference up to 1°C, seniors not until 5 °C.
- The efficiency of the cold vasoconstriction is worse.
- Shivering as a protection against cold in seniors decreases or even disappears.
In summary seniors are characterized with the lower heat production and less ability to avoid the heat losses. The physician must be careful before he/she gives a medical opinion to seniors about their ability to carry out a physical activity in the extreme cold.
Health risks during exercise in the cold results firstly from
After Tr falls below 34°C the hypothalamus begins to lose its ability to regulate body temperature. This ability is completely lost after Tr falls below 29°C. Humans die when their Tr falls to 24 - 25°C.
Cooling of the heart tissue leads via sinus node to a progressive decline of heart rate followed by serious arrhythmias and cardiac arrest. Zindler (1973) found in 1290 subjects with middle hypothermia (30–32°C) 63 ventricle fibrillations and 8 cardiac arrests. A well-known fact is that the incidence of the myocardial infarction increases in the cold.
- The influence on the myocardium
Physicians are often asked whether rapid and deep breathing of cold air could damage the respiratory tract. In fact cold air that passes through the nose, mouth and trachea is rapidly warmed, even when Ta is less then -25°C. However, mouth breathing, which often occurs during exercise, causes cold irritation of the mouth, pharynx, trachea and even bronchi when Ta falls below -12°C. Consequently the respiratory rate and volume decrease. These alterations can happen earlier in persons with predisposition to bronchospasmus.
- Respiratory tract
Hardening against cold is an instrument for the prevention of illnesses from cold. An increased immunity against respiratory infections was documented in subjects who regularly shower or bathe in cold water, as shown by the higher level of plasmatic IgA. Hardening results in an increased stimulation of immune system. The organism then easily manages common situations arising as a result of a relatively slight and short-term cold exposure.
Hardening reaches high-quality by combination with a physical activity.
Sauna is also an important instrument for hardening.
We start with Ta over 15 °C. The first exposure in summer light clothing (drill shorts, T-shirt) should not exceed 15 minutes. Continual exercise is necessary as a prevention from chill and shivering. The target is 10-20 minutes of outdoor training in any weather.
Water hardening is the most effective way.
We start with washing in cold water, preferably in the morning. A cold shower should follow later. We begin with a 10-second period, which is extended gradually. After each warm shower or bath, a cold shower should follow.
Cold showers 2-3 times weekly are sufficient for a good degree of hardening. Using cold showers regularly we can bathe outdoors in the summer in any weather. However we do not enter into the water when either cold or “heated”. A short warm up before and after swimming in cold weather is recommended. We do not stay out in a wet swimsuit.
The aim for hardening is not for making records. It is a natural way for health improvement.
I love this site!!!
I would add one thing. (I haven't read the entire article yet.) It should be protection against heat loss (not losses).
I would like to thank you all (especially Anglika of course) for your help. My friend is very thankful for it. Thanks again, and may the people you meet be as kind to you as you were to me.