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.
Exercise Physiologist We prevent and treat a diverse range of injuries using hands on exercise modalities as well as the most sophisticated electrotherapy technology to get the best.
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