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Acute Effects of exercise

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Tim Lane

on 9 May 2016

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Transcript of Acute Effects of exercise

The acute effects of exercise are sudden, initial responses of the body and its symptoms to exercise.

There are acute effects on 4 main parts of the body- Muscular, Respiratory, Cardiovascular and Energy systems.
The acute affects of exercise on the Respiratory system
Acute effects of exercise on the Musculoskeletal system
Increase in range of movement
Acute effects of exercise on the Energy system
The acute effects of exercise on the Cardiovascular system
Acute Effects of exercise
One acute affect of exercise on the Cardiovascular system is an increase in body temperature. This is because the movement your body is doing generates heat, therefore increasing your body temperature. However body temperature becoming too high can be dangerous, so therefore your body has to maintain a safe balance. To cool the body down heat is directed to the surface of the skin where it can be lost. This is why it's common for skin to turn a pink/red colour when exercising.
Another acute affect of exercise on the cardiovascular system is increased heart rate. Heart rate increases during exercise as the working muscles need a greater supply of oxygen, so therefore the heart has to pump more blood around the body to meet this demand. Prioreceptors detect movement, and Chemoreceptors cause a drop in the pH level (Co2)
An increased heart rate causes adrenaline to be released into the blood stream.
Vascular shunt is another acute affect of the cardiovascular system during exercise. This is the process of the body redirecting oxygenated blood to the exercising muscles. It occurs in the arterial side of the capillary, using the pre-capillary sphincter, which is a ring of smooth muscles which reduce blood flow to the non-exercising muscles. therefore a greater blood flow is directed to the working muscles to supply them with more oxygen.
Another way that blood is redirected to the working muscles is through Vasoconstriction. As soon as your body starts to exercise, the blood vessels around your major organs (stomach, kidney etc) will begin to constrict, meaning that more blood can flow to the working muscles and supply them with oxygen. The blood vessels around the working muscles would Vasodilate, so that heat can escape through the surface of the skin and keep the body cool.
One acute affect of exercise on the respiratory system is increased breathing rate. Breathing rate increases during exercise because our bodies demand for oxygen and the volume of each breath increases, as more is needed to supply the working muscles and allow them to keep functioning. For our breathing rate to increase, that rate at which we inhale (Inhalation) and exhale (Exhalation) has to increase.

A sporting example of an athletes heart rate increasing is a when the starting gun starts at the start of a 100m sprint. This is because their body releases adrenaline, which effectively increases heart rate.
A sporting example of Vascular shunt during exercise is a cyclist. When cycling your legs require a greater supply of oxygen than other parts of your body such as your arms and vital organs. Therefore in these parts of the body the blood vessels would vasoconstrict, so a greater blood supply would be sent to the legs to supply them with oxygen.
A sporting example for increased body temperature is Mo Farah at the end of a 10,000m race. He would have produced a lot of heat through a sustained physical activity. One way that his body will cool itself down is by the blood vessels vasodialating to let heat escape from the surface of his skin. He would also produce sweat, which when evaporating cools down his skin.
Neural Control
To allow our bodies to inhale and exhale air, we have nervous control of respiration. There are two nerves that travel from the brain to the body. The Intercostal nerve travels from the brain to the Intercostal muscles, and the phrenic nerve travels from the brain to the Diaphragm. As we exercise, these movements speed up, as our body’s demand for oxygen to the working muscles increases.
Chemical Control
There are other factors that affect the control of breathing. For example when exercising our Chemoreceptors can detect the increased levels of Co2 in our body, produced from the working muscles. Therefore when exercising our breathing rate increases.
Our RCC in the brain can also detect a change in the pH, as the acidity would increase. This is a sign for the body to increase respiration if the acidity had increased, and decrease respiration if the acidity had decreased.
Finally, the Hering-Breruer Reflex are stretch receptors that prevent the over inflation of the lung. If a lung was to over inflate, it could lead to it bursting.
Tidal Volume
Tidal volume measures the amount of air inspired during normal, relaxed breathing, measured in milliliters. The average tidal volume for a Male is 600ml and 500ml for Females. During exercise, tidal volume increases due to the body’s greater demand for oxygen to the working muscles.
Muscle Fibre Tears
Increase in Muscle Pliability
Before exercising, it is important that we warm up thoroughly. A warm up should include stretching muscles to prevent injury, as cold muscles can tear and pull when you begin to exercise. Warmer muscles are therefore more efficient.
An example of how stretching muscles improves performance is a gymnast stretching before an event. With stretching, their muscles become more flexible, meaning they can perform more complex moves and score higher.
Increase in Blood Supply
As we start to exercise, more blood is pumped around the body to supply the working muscles with oxygen. When we exercise our muscles contract and relax which produces heat. This heat being produced causes thermoregulation, which helps to maintain the bodies core temperature.
When the bodies blood supply is increased, it also causes the blood vessels to Vasodialate. This is where the capillaries expand and move closer to the surface of the skin, meaning more heat is lost through the skin. This makes sure that your bodies temperature doesn't get to high during exercise.
There are tiny tears in the muscle fibres that occur when we exercise. These muscle fibre tears cause swelling in the muscle tissue, as it is damaging the nerve endings in the muscle fibres.
The repairing of the muscle isn't an acute factor of exercise, but when the muscle fibre tears repair themselves they repair stronger and thicker than they previously were. This therefore makes the muscle more efficient. Pain can often be a sign of the muscle repairing itself, which is why you may feel soreness in the days following exercise.
As we move during exercise, heat is produced through the contracting and relaxing of muscles. Because of this heat being produced it warms the joints, meaning there is less resistance when we move. As the joints warm, it also makes the Synovial fluid in the joints become less viscous, meaning that the joints have easier movement.
An example of how muscle fibre tears improve an athletes performance is a weightlifter. This is because after a long period of time this will help the athlete build bulk, so therefore be able to lift heavier weights.
An example of increased blood supply in sport is a marathon runner. As they run the contracting and relaxing of their muscles produces heat, causing Thermoregulation and their blood vessels to Vasodialate. This is important because it means that heat can be lost through the surface of their skin, so that their body temperature doesn't become too high.
An example of how an increased range of movement would benefit a sports person is a football goalkeeper. With an increased range of movement they would be able to make more difficult saves, as they can reach and stretch further.
ATP/CP
The ATP/CP system, also known as Adenosine Triphosphate, is made up of one molecule of Adenosine and 3 molecules of Phosphate. When your body uses short bursts of energy, a bond between the chemicals is broken. This produces 2-3 seconds of activity.
The ATP/CP system is useful as it gives an athlete a short burst of energy, without fatiguing by products such as lactic acid being produced. The recovery time for the energy system is only a few minutes, so it can be used repeatedly throughout an event.
A sporting example of how the ATP/CP system can be used is during a netball match. When a center pass is being taken, the Goal Attack and Wing Attack would drive out into the center third to receive the ball from the Center. This is am explosive movement that only lasts a few seconds, which is why the ATP/CP system would be used.
Lactic Acid
The lactic acid system is produced through the breakdown of glucose. This glucose enters our body through the carbohydrate we eat being digested. Before the energy system turns to lactic acid, it first form pyruvate acid. Because no oxygen is present, this pyruvate acid then forms lactic acid.
The lactic acid system is beneficial to an athlete because it allows short bursts of energy to be produced, that are longer than the ATP/CP system produces. Recovery is important after using the lactic acid system as the lactic acid waste product that is produced needs to be removed from the muscles, to prevent soreness the next day and blood pooling in the muscles.
A sporting example of when the lactic acid system is used is in a 100m sprint race. This is because it is around 10 seconds of intense exercise, meaning the ATP/CP system cant be used for that long and your body hasn't started to work aerobically.
Acute responses to Exercise
The initial responses to exercise of the three systems (cardiovascular, respiratory, and muscular) are called acute responses.

The level of response is dependent on the intensity and type of exercise being undertaken.
During exercise, the cardiovascular system needs to deliver greater amounts of oxygen and energy substrates to the working muscles, in order to meet the increasing energy demands of the activity.

The focus is on getting more blood (the respiratory system will increase the O2 and CO2 removal in the blood) to the working muscles to meet this need and to speed up the removal of carbon dioxide and other waste products.
Cardiac output (Q)
is the product of
stroke volume (SV)
, which is the amount of blood pumped out of the left ventricle of the heart per beat, and
heart rate (HR).

Q (liters per minute) = HR (beats per minute) × SV (liters per beat).
Calculate the Cardiac output for the following tbl.
A lower heart rate, together with an increased stroke volume, indicates an efficient circulatory system. For a given cardiac output, the heart does not have to beat as often to eject the same amount of blood.
When the body begins to
exercise, both stroke volume and heart rate will increase
to increase the cardiac output of the heart.

At
rest, the heart will eject only about 40 to 50 per cent of the blood in the left ventricle
. During exercise, a stronger ventricular contraction causes greater amounts of blood to be ejected; this causes the increase in stroke volume.

Stroke volume increases to a maximum during submaximal workloads; any further increase in cardiac output is a result of an increase in heart rate.
Heart rate is the most important factor in increasing cardiac output during exercise.


During submaximal exercise, heart rate will increase until the oxygen demands of the activity have been met. It will then level off, as the body has reached a
steady state,
where oxygen supply equals oxygen demand.

With increasing workloads, heart rate will increase linearly until maximum heart rate (max HR) is reached.
If the exercise duration continues
past 30 minutes, heart rate will continue to increase but stroke volume will decrease.
The
changes in heart rate and stroke volume are equal in size but opposite indirection.
Therefore
cardiac output stays the same
to meet the demands of the b
\
exercise.
Blood Pressure
During exercise, the increase in
cardiac output results in an increase in blood pressure.

Exercise using large muscle groups (such as running or swimming) affects systolic blood pressure more than diastolic blood pressure.
What is systolic BP and diastolic BP?

Strengthening exercises cause greater increases in systolic and diastolic blood pressures
, but the changes in heart rate and cardiac output are less.
Venous Return
As the heart can
eject only as much blood as it has in its ventricles
, it is important for an increase in cardiac output to be
accompanied by an increase in venous return.

During exercise, the venous return is increased via three mechanisms: the muscle pump, the respiratory pump and venoconstriction (constriction of the veins). (See Figure 4.6.)
The muscle pump
is a result of the mechanical pumping action caused by repetitive muscular contractions. When the muscles contract, the veins are squashed together and the blood in them is forced towards the heart. Valves in the veins prevent the blood from flowing backwards; veins are a one-way street for blood flow. Then when the muscle relaxes, the veins fill with blood until the next contraction and the process continues, resulting in a ‘pumping’ action.
T
he respiratory pump u
ses a similar mechanical action to assist venous return. During inspiration (breathing in), the diaphragm increases abdominal pressure, and veins in the thorax and abdomen are emptied towards the heart. Then during expiration (breathing out), the process is reversed – the veins fi ll with blood ready to be emptied again. Venous return is promoted simply through breathing. During exercise, when venous return needs to increase, respiratory rate increases, which makes the pump more effective.
Ve
noconstriction i
s a reflex controlled by the central nervous system, and assists in venous return. Venoconstriction reduces the capacity of the venous system, forcing blood to be pushed out towards the heart.
Blood volume
During aerobic exercise, blood volumes decrease.

Studies have shown that plasma volume can decrease by 10 per cent in prolonged endurance activities.

Plasma volumes decrease rapidly within the first five minutes of exercise, but then stabilise
Redistribution of blood flow
Blood flow is redirected away from
the spleen, kidneys, gastrointestinal tract and inactive muscles t
o the working muscles
, so that these muscles receive the greatest percentage of the cardiac output (see Figure 4.7).
V
asoconstriction
occurs in the arterioles supplying the inactive areas of the body and v
asodilation
occurs in the arterioles supplying the working muscles.
Oxygen consumption (VO2) and arteriovenous oxygen difference (a-vO2 doff)
Oxygen
consumption is the volume of oxygen that can be taken up and used by the body.

As i
ntensity of exercise increases, so does oxygen consumption.
This is a direct result of an increase in cardiac output (as discussed earlier) and an increase in the arteriovenous oxygen difference(a-vO2 diff) (see Figure 4.8).

At rest, arterial blood releases as little as 25 per cent of its oxygen content. During exercise, oxygen extraction can approach 100 per cent.
Receptors
an organ or cell able to respond to light, heat, or other external stimulus and transmit a signal to a sensory nerve.
a molecule in a cell membrane, which responds specifically to a particular neurotransmitter, hormone, antigen, or other substance.
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