Monday, 16 July 2012

Responses Of The Body To High Altitude, And Their Effects On Exercise And Sports performance


It is challenging for athletes to maintain a suitable body temperature so their body can perform and function effectively while training or competing. Depending on the conditions the athlete has to try avoid over heating or losing too much body temperature.

Responses of body to high temperature

The body can react to the heat an enable an athlete to cope with variety temperate changes. During exercise the body’s metabolic rate can increase and this increased in energy consumption can raise the body temperature significantly.

Sweating
This is the most well known bodily response to high temperature. Sweating involves the secretion of sweat on to the surface of the skin. Sweating provides little or no cooling if it drops off the body but provides effective cooling process if the sweat on the surface of the skin evaporates.

Function of the hypothalamus
The hypothalamus has a number of roles within the human body its most important is that of the body’s thermostat. The hypothalamus contains the central point within the body for temperature regulation. A group of specialised neurones at the base of the brain help to regulate body temperature within a narrow band around 37°C. The hypothalamus itself receives a more generous blood supply than any other brain structure. It is mainly through this increased blood supply that it is in an ideal position to watch over or administer body temperature. The hypothalamus carries out this role to allow normal bodily function and to protect the body’s core temperature by initiating responses when that temperature changes due to heat gain or heat loss.

Methods of heat loss

Athletes get rid of heat in different ways including through conduction evaporation radiation and respiration. Each has a different level of efficiency depending on characteristics.

Conduction
Conduction involves warming the air surrounding the body or warming any cooler surfaces in contact with the skin. Conduction involves the transfer of heat through a solid, gas or a liquid by contact. The rate of heat loss depends on the temperature difference between the skin and surroundings. The quicker the air moves around the body the greater the quantity of heat conducted from the body. 

Evaporation
Evaporation is the body’s major defence against overheating. Water vaporisation lost by breathing or sweating transfers heat from the body to the environment. The cooling process occurs when sweat reaches the surface of the skin and evaporates. As the air surrounding the body becomes saturated with evaporated fluid new air then arrives to accept further evaporated sweat.

Radiation
Radiation is the transfer of heat from one object to another without contact6. Athlete’s heat radiates heat towards cooler objects. At rest radiation is the main method of dissipating body heat.

Respiration
Respiration combines the processes of evaporation and connection. Moisture is lost when it is exchanged with drier air of the surrounding environment. In addition a small percentage of body heat is lost when warming the cold air entering your lungs.

Effects of high temperature

Hyperthermia
Overexposure to hot and humid conditions can result in the normal heat loss processes becoming ineffective. This is when hyperthermia is likely to follow which will result in the hypothalamus itself being compromised. A core temperature greater than 40ºC increases metabolic rate, which increases heat production. The skin then becomes hot and dry as the temperature continues to rise to an extent that organ damage becomes a possibility. This condition is known as heatstroke and can be fatal if corrective measures are not implemented immediately. This usually involves cooling the body in water and administering fluids.

Dehydration
Dehydration is a condition of excessive water loss. When water output exceeds intake over a period of time and the body is negative in its fluid balance, dehydration results. A serious consequence of dehydration results in a lowering of blood plasma levels which leads to an inadequate blood volume to maintain normal cardiovascular function. Loss of fluid as seemingly little as 1 per cent of total body weight by sweating will lead to a decline in performance. Dehydration is best avoided by drinking plenty of water. When large amounts of water are being lost through perspiration, maintaining electrolyte balance becomes an issue for the athlete, which may result in salt depletion. This is caused by sweating and can cause a range of further symptoms beyond that of simple dehydration. These include tiredness, irritability, fainting, cramps and an overall loss of performance.

Effects of high temperature on sports performers
Too much body heat generated during exercise reduces performance. As body temperate rises blood flow to the skin increases and the body attempts to cool itself by sweating. During intense exercise the body temperature can rise as high as 39 ºC and muscle temperate slightly higher. Theses temperatures make exercise difficult because the body and muscles are competing for blood. Oxygen is needed for the cooling process and reduces the amount of oxygen available for vital organs which can lead to severe health risks as well as a drop in performance.

Responses of body to low temperature

Shivering
Shivering is a series of involuntary contractions of muscle tissue in response to a cold environment. It is designed to increase body temperature. Shivering is effective because the rapid muscle activity produces heat.

Vascular adjustments
Restricting blood flow to the skin and surface areas is not a problem for short periods. However, if this is extended over a long period of time, skin cells deprived of oxygen and nutrients from the blood begin to die. This condition is known as frostbite and can be very serious indeed.

Effects of low temperature

Hypothermia
Hypothermia is a low body temperature resulting from uncontrolled exposure to the cold. The effects of hypothermia are far reaching: it affects vital functions such as breathing rate, blood pressure and heart rate, while decreasing cellular function. Drowsiness is a common symptom of hypothermia, followed by a feeling of comfort felt by the victim, regardless of how cold they actually are. Shivering generally ceases when the body has used up its heat-generating abilities and occurs when the core temperature is drops below approximately 32 º C. If left uncorrected and the body temperature lowers to the region of 24 º C, death by cardiac arrest is likely.

Effects of low temperature on sports performers
The effects of cold in sport can be more harmful than the effects of heat. A danger is the increased risk of torn muscles or tendons. The greatest risk is hypothermia. Exercising in cold weather causes the body to maintain its core temperature by shunting blood away from the fingers and toes minimising heat loss. Moderate hypothermia causes muscular fatigue, poor coordination and numbness. Server hypothermia can result in cardiac arrest.   

Altitude 

Altitude can be defined as a measurement of vertical elevation it is usually referred to in relation to ground or sea level

Responses of body to high altitude


Hyperventilation
Hyperventilation – breathing more than what the body actually needs.
Hyperventilation involves the increased ventilation of the lungs caused by an increase and frequency of breathing due to impaired gaseous exchange in the lungs. In the UK, the majority of the population live between sea level and an altitude of approximately 500 metres. The differences in barometric pressure within this range are not enough to cause any problems when spending time in higher-altitude areas. When breathing normally, the breaths are varied to maintain normal carbon dioxide levels and supply appropriate levels of oxygen to the body’s tissues. This is done automatically by measuring the carbon dioxide level in the blood. At altitude, the air is oxygen-deficient, so the resultant low carbon dioxide levels cause the brain’s blood vessels to contract. This results in reduced blood flow to the brain accompanied by spells of dizziness or light-headedness. This is when athletes realise they are experiencing hyperventilation as a consequence of training or competing at altitude without preparation. When an athlete leaves sea level and goes to a mountainous region, where air density and pressure are much lower, the body responds to this environment in a variety of ways. Initially the body responds with headaches, dizziness and nausea due to the respiratory adjustments. This step is known as acclimatisation. In time, the athlete will adjust to the new environmental surroundings accordingly.

Tachycardia
Tachycardia is resting heart rate that is higher than normal more than 100 beats per minute. Tachycardia can occur as consequence of low body temperature. There are however other causes of tachycardia such as stress heart disease and drugs.

Effects of high altitude

There are distinct environmental differences at high altitude which include, less partial pressure of oxygen, dryer air, cold temperatures and greater exposure to U.V radiation.

Reduction in partial pressure of oxygen
Decreases in arterial oxygen pressure cause the central chemoreceptors to become much more responsive to an increase in carbon dioxide. This stimulates the peripheral chemoreceptors, which leads to an increase in ventilation as the brain attempts to restore gaseous exchange to a previously normal level. Given that there is less oxygen available at high altitude, this always results in lower than normal haemoglobin saturation levels in an athlete’s blood. At 5,000 metres above sea level, for example, the oxygen saturation in arterial blood is approximately 70 per cent. Therefore, at 5,000 metres there is less oxygen available in the blood to assist cellular respiration and bodily function. If an athlete has not acclimatised to these conditions, the lack of oxygen readily available from arterial blood may serious impair physical activity.

Reduced maximum oxygen consumption (VO2 max)
Competing at altitude means a lack of oxygen which the body has to deal with. When competing at altitude, the body has to compensate for a lack of oxygen. There is, for example, an estimated drop in VO 2 maximum of 2 per cent for every 300 metres above 1,500 metres above sea level. This drop in VO 2 maximum means an athlete’s oxygen uptake decreases, which can affect athletic performance, particularly during endurance-based events.

Adaptation to altitude
Although body tissues receive adequate oxygen at normal conditions at altitude, problems arise when athletes are required to undertake strenuous activity and the demands of the cardiovascular and respiratory systems are increased.  Unless the athlete has undergone a period of acclimatisation, such activity, when combined with the conditions of altitude, may lead to the body’s tissues becoming hypoxic. There are essentially three major changes that occur following acclimatisation. Increased haemoglobin concentration: during acclimatisation, there is an increase in red blood cell count and, consequently, an increase in haemoglobin concentration. The increase in red blood cell count is brought about due to an increase in the manufacture of red blood cells in the bone marrow as a response made by the body to the altitude. Increased breathing rate: to compensate for the decrease in the partial pressure of oxygen in the lungs, the breathing rate of an athlete increase. Cellular changes: altitude causes an increase in the myoglobin content within cells, together with an increase in the number of mitochondria.

Effects of high altitude on sports performers
At high altitude there is less oxygen which creates problems for sports performers. Anaerobic events require little oxygen so it won’t affect them as much as endurance athletes. A number of changes occur when training or competing. High altitude training is an effective performance enchaining tool as the ability of an athlete to utilise greater amounts of oxygen improves performance. The benefits of high altitude training continue for several weeks after the return to sea level. Phoenix suns basketball team trained using high altitude indoor training facility. They used the CAT altitude training which is an indoor facility where they take oxygen out of a room when athletes are training this makes it feel like their training at altitude. This made them work at hard intensity but not to their maximum because they get tired quicker.   

Everest is 29000 ft. A climber climbed Mount Everest and had a 34% oxygen saturation in blood which is the lowest ever seen in a living being.

The air force trains their Pilots by taking away the oxygen which is sudden decompression. The pilots become light headed and have tingling hands, they also care what is happening.      

Balloonists when the first started going higher than usual started to lose their feelings in legs, they also lost sight. The first people trying to break record of going the highest altitude managed to descend before being killed the descent caused them to recover. 

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