Physiological effects of the environment on the athlete

AS and A Level Physical Education (Sport & Coaching)

Physiological effects of the environment on the athlete

As an athlete passes through an athletic career, numerous things happen which bring changes in his environment. In the early stages, the most common changes involve long, tiring journeys, sometimes combined with a stay for a number of days in an unfamiliar place. Later in the athlete's career there are more serious changes to take note of, and to prepare for. There are three environmental conditions that an athlete will have to learn how to acclimatize to, these are , and water.

Altitude

At altitude there is reduced air resistance, suggesting an advantage in activities involving speed, i.e. sprints. The force of gravity is reduced, suggesting an advantage where relative and maximum strength is critical.

Some of the immediate effects of exposure to altitude are, increased breathing rate, increased heart rate, nausea, headache, sleeplessness and decrease in . The total effect of these adjustments is a reduction of work capacity.

The long term effects of continued exposure to altitude include, increased haemoglobin volume and concentration, increased blood viscosity, more capillary’s, lower V02max, decreased lactic acid tolerance and reduced stroke volume.

For short term training at altitude, the various benefits associated with it can be offset by other fundamental drawbacks such as, strange diet, different surroundings and homesickness.

On return from altitude training performances at sea level appear to peak between the 19th and 21st day and then again between 36 days and 48 days performance improves.

Temperature

The ability to perform vigorous exercise for long periods of time is limited by hyperthermia (over heating) and loss of water and salt in sweating. Athletes should know the hazards of vigorous exercise in hot, humid conditions and should be able to recognize the early warning symptoms that precede heat injury.

The circulatory system functions first to deliver nutrients to the working tissues and remove the waste products; and secondly to regulate the transfer of heat from active muscles to the body surface. It is because of this added demand on blood flow that body temperature regulation, and circulatory capacity, are significantly influenced by the environmental temperature and humidity. When performing in warm, humid conditions the circulation cannot both supply nutrients to muscle and regulate body temperature to the complete satisfaction of the body. As a result, the athlete's performance is decreased, and overheating becomes a serious problem.

Low levels of dehydration can impact performance. E.g. An athlete running 120 seconds over 800 meters, then if low levels of dehydration occur his or her time would be reduced to 132 to 144 seconds.

Thermoregulation

Thermoregulation is the process of maintaining a constant body core temperature. Our average body temperature is 37°C. The core of the body consists of the head chest and abdomen.

The skin temperature of the body can vary a great deal, however, if the core temperature increased or decreased by 1°C or more, this will effect an athlete’s physical and mental performance. Larger changes in core temperature will lead to hypothermia or hyperthermia, both of which can be fatal. In order to assess the core temperature of a person, there are a number of places a thermometer can be placed, the mouth, ear and under the arm. Doctors and nurses prefer to the ear as it gives the most accurate reading.

Heat Transfer

There are four main methods by which the body can lose and gain heat.

Conduction

Conduction involves the direct transfer of heat from one object to another. Normally this method of heat loss is not significant unless the person is exercising in cold water. This is because water conducts heat away from the body approximately 25 times more quickly than air. E.g. If a swimmer was competing in a cross channel race they would have to take precaution before entering the cold sea otherwise they might run the risk of hypothermia.

Convection

As air molecules are moved across the body, heat will be lost because convection air currents carry the heat away. Wind will increase the flow of air over the skin, thus increasing the amount of heat lost through convection. This is why a breeze feels good on a hot day, and why we use fans to keep use cool.

Radiation

At rest radiation is the main method of heat loss. It is the process by which heat is lost (via electromagnetic waves) to cooler objects in the environment, such as a cold floor, walls etc. How much heat a person loses through radiation is determined by their size, mass and body composition. People with a high body fat percentage will lose less heat through radiation than a person with a low body fat percentage, because body fat acts as an insulator to radiative heat loss. A tall skinny person will lose more heat through radiation than a sort stocky person. In warm climates, the sun radiates heat to the body, which will increase its temperature. This makes getting rid of excess heat during exercise more difficult, because getting rid of heat via radiation is impossible when both objects are the same temperature.

Evaporation

Evaporation of sweat from the body is the major method of heat dissipation, particularly during exercise. Heat is transferred continually to the environment as sweat evaporates from the skin surfaces and produces a cooling effect. However, if the environment is humid, evaporation heat loss is reduced. Heat is only lost when sweat evaporates, which it will not do in humid conditions. Therefore, on a hot, humid day, an athlete can be dripping with sweat, but because the sweat is not evaporating it does not cool them down.

Exercising In Heat

Exercise increases metabolic ...

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Evaporation

Exercising In Heat

Exercise increases metabolic rate by 20 to 25 times, and could increase core temperature by 1°C every six minutes if thermoregulation did not take place. This would result in death from hyperthermia if exercise continued. Therefore, with the added stress of a hot environment, an exercising athlete has to maximize heat loss in order to perform to the best of their ability and to avoid hyperthermia.

There are three major forms of hyperthermia

Heat Cramps
Heat Exhaustion
Heat Stroke

Heat Cramps

Heat cramps are muscle spasms caused by heavy sweating. Although heat cramps can be quite painful, they usually do not result in permanent damage.

Heat Exhaustion

This is more serious than heat cramps. It occurs primarily because of dehydration and the loss of important minerals. In order to lose body heat, the surface blood vessels and capillaries dilate to cool the blood. However, when the body is dehydrated during heat exhaustion, these dilated blood vessels constrict and significantly reduce heat loss. This can be observed by looking at the face of an athlete suffering from heat exhaustion, as they will look very pale instead of rosy cheeks.

If a person ignores the symptoms of heat exhaustion and continues to exercise, they will suffer from heat stroke, which is a life threatening condition and has a high death rate. It occurs because the body has depleted its supply of water and salt, and results in the persons body temperature rising to deadly levels.

Heat loss in a hot environment

In the brain there is a thermostat called the “hypothalamus” which protects the body from overheating. It receives information about the temperature of the body via two sources, indirectly from the thermal receptors in the skin and directly by changes in blood temperature.

Heat loss through radiation is not possible if the environment is hotter than the person exercising. Therefore, there are only three forms of heat loss available to a person exercising in a hot environment.

The first form of heat loss is conductive. This occurs by the peripheral blood vessels dilating and bringing blood closer to the skins surface. This results in the rosy coloured skin associated with hot athletes. The heat from the blood warms the air molecules around the person and any cooler surfaces that come into contact with the skin. This can be related to an athlete who is really warm after running a race jumping into a cold swimming pool or getting a cold shower.

The second form of heat loss is convective. This occurs much more rapidly if there is increased airflow around the body. E.g. If an athlete was running on a treadmill and had a fan blowing towards them. If there is a little air movement, the air next to the skin is warmed and acts as a layer of insulation that minimizes further convective heat loss. If the warmed air surround the body is frequently changed due to increased air currents, heat loss through convection will continue to remove excess body heat.

The third form of heat loss is evaporative. This occurs when sweat evaporates from the skin, which cools down the skins surface. This has the effect of cooling the blood as it travels through the blood vessels that are close to the skins surface. In order for evaporative heat loss to occur maximally, the person must be hydrated and have normal levels of salt.

Heat Acclimatization

Athletes are able to cope much better with hot or humid conditions if they are acclimatized. Complete heat acclimatization requires up to 14 days, but the systems of the body adapt to heat exposure at varying rates. The main effects of acclimatization are: -

Heart rate goes down.
Blood plasma volume goes up.
Skin blood flow goes up.
Sweating occurs at a lower body core temperature.
Sweat rate goes up.
Sweat becomes more dilute.

In the first 5 days, plasma volume expands as a result of increased proteins and increased sodium chloride (salt) retention. This increased plasma volume leads to a 15-25% reduction in heart rate at rest and during exercise from when first exposed to the hot environment.

The sweating mechanism is also adapted in three main ways: -

Earlier onset of sweating
Increased amount of sweating
Increased dilution of sweat

Once a person has started to acclimatize they will begin to sweat at a lower body core temperature. They will also produce more sweat in order to maximize evaporative cooling. The maximal non-adapted sweat rate for a male is one litre per hour, however, after acclimatization, the sweat rate can double to two litres per hour. Sweat becomes more diluted due to conservation of salt. The salt losses in sweat and urine decrease during days 3-9 of heat acclimatization.

Exercising In Cold

The effect of a cold environment on exercise performance depends largely on the severity of the cold and the type of the exercise performed. Exposure to a moderately cold environment may actually have a positive effect on performance, as the cardiovascular system no longer has to divert blood to the periphery for heat loss in addition to supplying the exercising muscles with blood. This results in less stress being placed on the heart than when exercising on the heat. Therefore, it is not surprising that the record performances during long distance running and cycling are usually in cool climatic conditions. However, exposure to extreme cold, such as cross-country skiing, may cause an athletes core body temperature to drop and maximal aerobic endurance (VO2 max) to be reduced, which will make an athletes performance suffer.

If a person is exposed to a cold environment they may suffer from frostbite or hypothermia.

Frostbite

This usually occurs in a person’s fingers or toes. It happens when a part of the body becomes extremely cold, which significantly reduces the blood supply to that area. This results in the blood tissue freezing. The ice crystals that form will rupture and destroy the body’s cells. The involved region turns a deep purple or red colour and has blisters, which are usually filled with blood. This tissue will have to be amputated to prevent infection from spreading to other parts of the body.

health-pictures.com/ frostbite-picture.htm

Hypothermia

This is defined as a drop in the body’s normal core temperature to 35°C or below. The condition usually comes on gradually and its severity varies in relation to how low the core body temperature drops. If it drops to 30°C or below this can lead to cardiac and respiratory failure that is soon followed by death.

Methods of gaining heat in the cold

When a person is exposed to a cold environment at rest, the body temperature attempts to prevent heat loss as well as to increase heat production. It does this via three main physiological mechanisms: -

Constriction of the blood circulation
Non-Shivering thermogenesis
Shivering

First of all, the body will decrease the blood supply to the peripheral circulation by constriction of the peripheral blood vessels (vasoconstriction). The purpose of this is to keep the blood close to the body core and redirect the blood away from the body’s extremities and skin surface, where it would be cooled down by the environment.

Secondly, a person will experience an increase in their metabolic rate, which is brought about by a increased release of the hormones thyroxin and adrenaline. An increased metabolic rate will generate body heat. This process is called non-shivering thermogenesis.

Lastly, a person will experience a rapid involuntary cycle of contraction and relaxation of skeletal muscles, which is known as shivering. The process of shivering can actually increase metabolic rate to 4-5 times above resting heart rate.

Cold Acclimatization

The main method by which an athlete can attempt to acclimatize to a cold environment is to increase their fat levels in the body. This would have the effect of increasing the body’s insulation to the cold, thereby reducing heat loss. However, in reality an athlete rarely want to increase their fat proportion, as excess fat will increase their body weight. Depending on the athlete’s sport, this increase in body weight would usually decrease their performance. Therefore, the only real option for an athlete is to ensure they are wearing the appropriate clothing to protect them from the environment. Layered clothing has been found to provide the best insulation against the cold. In addition to this, the clothing should be breathable. This is because during exercise, the athlete will sweat. This sweat must be allowed to evaporate, if it doesn’t then the clothing will become wet. This then increases heat loss by conduction and evaporation. Therefore, clothing worn close to the body should be made of material that can transport moisture away from the body’s surface to the next clothing layer for evaporation. Also the head should always be covered, as 30-40% of body heat is lost through the head.

The new All Blacks rugby jersey is breathable to allow insulation but also evaporation via sweating.

Exercising in water

When a person is submerged, their resting heart rate will decrease. This is a attributed to the pressure of water on the body producing central pulling of the blood. This extra pressure acts to increase the rate of blood returning to the heart, which will result in an increased stroke volume. This in turn produces a lower heart rate.

However, when exercising in water an athlete must use more energy than when exercising on land in order to maintain buoyancy. When a person is swimming they must also maintain a horizontal position in the water and overcome drag forces which are imposed on the swimmer by the water itself. As a result, swimming a given distance will use 4 times more energy than running the same distance.

Apart from swimmers who train regularly in water some athletes may undergo rehabilitation exercise in the water if they are recovering from a sports injuries to the lower body. This is because the athlete can perform non-weight bearing exercises and still carry sport specific exercises, such as the running action. As the water supports the athlete’s body weight there will be much less stress placed on the injured body part than when exercising on land.

The main problem that a person may experience while exercising in water is the increased heat loss that can occur if the water is cold.

Cold water immersion

Water is deemed to be cold if it is less than 21°C. If a person swims in cold water, they will lose body heat quickly through conduction, and will try to increase their body heat by shivering. They will be using up energy trying to maintain their body heat, and the swimming action itself will also use up energy. If a person is exposed to cold water (less than 21°C) for long period of time, they will eventually become exhausted or fall unconscious. If a person falls unconscious in the water, this may well result in death from drowning.

Immersion in cold water can soon numb the extremities to the point of uselessness. Hypothermia quickly sets in, which will lead to unconsciousness and death. If a person is submerged in very cold water, the initial shock can place severe strain on the body, and produce instant cardiac arrest.

Altitude

The underlying problem with high altitude (>2000 m) is that there is less oxygen and while this may not be that threatening to individuals at rest it does pose a challenge to athletes. Of course for the pure anaerobic events no adaptation is required so this discussion is necessarily focused on endurance training and competition. In general the higher the altitude the longer it takes to adapt. Understanding the adaptation process and the things that you can do to aid it will make for a less taxing transition. A number of physiologic changes occur to allow for acclimatization at high altitude. These can be divided into immediate, which take place over several days, and long term which requires weeks to a few months.

The first thing that happens is your respiratory rate and heart rates speed up. This occurs both at rest and during sub-max. exercise. This helps offset the lower partial pressure of oxygen. You will not be able to reach your max VO2 so don't get frustrated. The faster breathing rate changes your acid-base balance and this takes a little longer to correct.

The longer term changes are

A decrease in maximum cardiac output a decreased maximum heart rate
An increased number of red blood cells
Excretion of base via the kidneys to restore acid-base balance. (Unfortunately, the net result is that you have less tolerance for lactic acid.)
A chemical change within red blood cells that makes them more efficient at unloading oxygen to the tissues.
An increase in the number of mitochondria and oxidative enzymes.

Problems that might occur

Diet

A high carbohydrate, low salt diet allows for better adaptation and less risk of "mountain sickness". Some people experience significant decline in appetite and the resulting loss of muscle mass may hinder performance. Iron is used to make hemoglobin and the demand for making more red blood cells may require iron supplementation -- especially in women and vegetarians. Mega doses of vitamins are not helpful and are potentially dangerous.

Fluids

Because mountain air is cool and dry you can lose a lot of water so be sure to maintain adequate hydration.

Alcohol

It is best to avoid alcohol consumption during the acclimatization period since it appears to increase the risk of "mountain sickness".

Workout Intensity

This will necessarily be lower until adaptation can occur. Pushing your workouts too hard may increase your risk of overtraining or injury. Additionally some people just do not adapt as well as others. There is not one workout program that is appropriate for everyone -- just like at sea level. It is best to keep a log in which you rate fatigue during workout and at rest, morning resting heart rate, weight, and mood. Correlate this with the intensity of your workouts and this will help mold a flexible routine that is right for you.

Performance

The body's adaptation to high altitude helps significantly but doesn't fully compensate for the lack of oxygen. There is a drop in VO2 max of 2% for every 300 m elevation above 1500 m even after allowing for full acclimatization. To fully appreciate this you have to realize that there aren't any world record times at high altitudes. The air density is much lower, thus wind resistance is much lower. Wind resistance is the cyclist’s biggest barrier to speed. If all other factors were equal, then there must be faster times at higher altitudes. Because there aren't, means that something else must have decreased. That something is the heart and lungs.

Furthermore, while adaptation to high altitude makes you better at high altitude it hasn't proved useful for making you faster at sea level. There is a lot of doubts that surround the belief of enhanced sea-level performance after altitude training, but the current scientific evidence is lacking. The reason is that some of the adaptive responses at high altitude are actually a hindrance at lower altitude. As more research is done then perhaps a training regimen that shows definitive improvement will emerge.

There is some more recent evidence to suggest that a "train-low, sleep high" approach may confer some advantages. In this scenario, training is carried out at low altitude, to push anaerobic threshold, and VO2 max, but sleeping is done at high altitude so that the hypoxic stress increases red cell mass. In a practical sense it may be difficult to construct, but if you are lucky enough to live in a situation that allows this type of training, it is worthy of consideration.

Summary

Whenever a team is changing environments, there are certain aspects they have to consider: -

The first thing to consider is the environment around you.

Is it: -

Hot
Cold
Metres above sea level
Water hot or cold

Hot Environment

If there environment is hot then there are certain adaptations that will occur in the athlete’s body. Exercise increases metabolic rate by 20 to 25 times, and could increase core temperature by 1°C every six minutes if thermoregulation did not take place. This would result in death from hyperthermia if exercise continued. Therefore, with the added stress of a hot environment, an exercising athlete has to maximize heat loss in order to perform to the best of their ability and to avoid hyperthermia.

There are three major forms of hyperthermia

Heat Cramps
Heat Exhaustion
Heat Stroke

The three main ways to lose heat & avoid these effects of exercising in heat

Conductive
Convective
Evaporative

Cold Environment

In a cold environment there are certain adaptations that will occur in an athletes body. The effect of a cold environment on exercise performance depends largely on the severity of the cold and the type of the exercise performed. Exposure to a moderately cold environment may actually have a positive effect on performance, as the cardiovascular system no longer has to divert blood to the periphery for heat loss in addition to supplying the exercising muscles with blood. This results in less stress being placed on the heart than when exercising on the heat. Therefore, it is not surprising that the record performances during long distance running and cycling are usually in cool climatic conditions. However, exposure to extreme cold, such as cross-country skiing, may cause an athletes core body temperature to drop and maximal aerobic endurance (VO2 max) to be reduced, which will make an athletes performance suffer.

If a person is exposed to a cold environment they may suffer from frostbite or hypothermia.

There are three main ways to avoid these effects: -

Depending on the how severe the temperature is athletes such wear the appropriate amount of clothing insuring the head is covered as this the main point of heat loss.
The clothing should be appropriate as when the athlete exercises they will sweat so the clothing needs to be breathable to allow evaporation of sweat.
The time spent in the environment should be keep to a minimum.

Altitude

Water