Cardiac Output - the definition of cardiac output is the amount of blood pumped out by the ventricles in a given period of time. One of the responses to exercise through the cardiovascular system would be would be an increase of cardiac output. Cardiac output is the average stroke volume x average heart rate, so if an athlete's stroke volume is averagely 75ml and heart rate is averagely 65 beats per minute, the average cardiac output would be 4875ml per minute. A trained or untrained athlete approximately has 5 litres of blood circulated around the body per minute, this means on average, about 1 litre of oxygen is made available for the body and its muscles.
An increase of cardiac output has a huge benefit on the body whilst running, this is because it increases the amount of blood pumped around the cardiac system meaning that the oxygen can be delivered faster to the working muscles when running, the higher the cardiac output, results in a better performance from the athlete, this occurs in both untrained and trained athletes. A key adaption of the steady state exercise would be the resting heart rate decreases over a long term basis, and the stroke volume ultimately increases, this resulting in a better cardiac output. An average cardiac output of an athlete is 4900ml per minutes, however a trained athlete could have an average heart rate of 50 per minute, but can have a stroke volume of 110ml resulting in a cardiac output of 5500ml which is considered a really fit state of cardiac output.
Heart Rate - the definition of heart rate is "the rate at which the heart beats per minute". Another response to exercise through the cardiovascular system would be the increase of heart rate. The heart rate increases due to the high demand of oxygen that the body requires in order to perform, the blood is pumped faster around the body due to an increase of heart rate, meaning more oxygen can get delivered to the relevant working muscle groups quicker. A runner's heart rate increasingly speeds up before and during exercise, due to body requiring more oxygen to deliver to the muscles that are working, this is done in BPM (beats per minutes) and the more BPM, means more oxygen and blood being pumped around the runners body. After exercise, the runners heart rate would deplete, die to the muscles not working so hard.
An average heart rate for an untrained man or woman is anything between 60 - 80 beats per minute, whilst a trained athlete can get a heart rate of 28 - 40 beats per minute. Heart rate begins to increase even before exercise, this is because of the anticipation before the exercise and this is called anticipatory response, so when running, the anticipatory response kicks in and prepares the body for the upcoming exercise. After the anticipatory response has kicked in the heart rate during exercise increases in direct proportion to the intensity of the exercise being carried out, this happens until the heart rate hits maximum rate.
The maximum heart rate of a person I calculated by subtracting their age by 220, so if the age of the athlete is 20, the athletes maximum heart rate would be 200 beats per minute. Although the heart rate increases rapidly during exercise, the heart rate will level off, this is known as steady state heart rate, however the steady state will increase within in hot environments, and this is through the increase of body temperature and is known as cardiac drift.
Stroke Volume - the definition of stroke volume is "the volume of blood pumped from one ventricle of the heart with each beat". Another response to exercise through the cardiovascular system would be the increase of the stroke volume, this happens due to the intensity of the exercises that you are performing, it reaches peak at submaximal exercise, but it doesn't increases at maximal exercise.
The average stroke volume of an average human is 50-70ml/beat, this can increase up to 110-130ml/beat, this increases due to the intensity of the activity. A trained athlete can get stroke volumes up to 90-110ml/beat, this can increase up to 150-220ml/beat. The greatest increase of stroke volume actually happens between the transition from resting and not exercising to moderate exercise, however when in maximal exercise, the stroke volume doesn't increase this is due to the left ventricle being unable to take in anymore blood/oxygen as its reached its full capacity, a runner is able to maintain the maximal activity because the heart rate and stroke volume being maintained at a pace.
Blood Flow - the definition of blood flow is "Blood flow is the flow of blood in the cardiovascular system". Another response to exercise through the cardiovascular system would be the increase of the blood flow through the cardiovascular system. This is where an increase of energy expenditure is occurring, and the blood flow needs to be adjusted in order for the cardiovascular system to run effectively and properly. There are two aspects that affect and aid the blood flow;
Vasodilation - the definition of this is "The dilatation of blood vessels, which decreases blood pressure". This ultimately is the increase of diameter of the blood vessels, the blood vessels include things such as the veins, arteries, capillaries and arterioles, this happens so that when the blood flow increases, it allows it to travel to the muscles faster, the blood/oxygen is supplied through the vessels or arterioles that are linked to the muscle groups. This will also cause the skin to blush, or turn slightly red, this is because it has allowed more blood to reach the skin. This happens when a runner exercises, the blood vessels will open up wider, allowing more blood and oxygen to get to the muscles faster, and it also allows more blood to be pumped around the body.
Vasoconstriction - the definition of this is "The constriction of blood vessels, which increases blood pressure". This is the opposite to vasodilatation and instead of decreasing the blood pressure, it increases it by tightening up the blood vessels and decreasing the diameter of the blood vessels itself, this happens through contractions of the muscle fibre that lie within the vessel walls, this type of contraction is involuntary and can't be controlled. This will cause the skin to turn quite pale and slightly whiter than normal, due to the lack of blood being allowed to reach the skin. This occurs in different occasions through a runner, and could be due to the fact that the warm-up before exercise wasn't carried out properly.
Blood Pressure - the definition of blood flow is "the flow of blood within the cardiovascular system". Another response on the cardiovascular system to steady state exercise of a runner would be the increase of blood pressure. This is where the vascular area of the blood flow increases by the dilation of the blood vessels that are active within the muscles. Blood forces through the blood vessels and returns to the heart by the alternate rhythmical contractions and the relaxation of the skeletal muscles create. Blood pressure increases for a numerous amount of reasons;
The heart rate and stroke volume increase because of the two different hormones that are release whilst exercising, these being adrenaline which is also known as epinephrine and noradrenaline, which is known as norepinephrine. These cause the heart to contract faster and harder, resulting in to more blood being pumped around the body. An example of this could be a water hose, where you turn the hose on higher, the water flows faster, and the hose swells, this is the increase of blood pressure.
Contracting muscles actually squeeze against the veins, which is why when you exercise, veins start to pop out more. This briefly but significantly increases the blood pressure.
Your systolic blood pressure is the pressure within your arteries, whilst your heart is pumping blood out, this is the main blood pressure type that rises. The diastolic blood pressure is the pressure during the relaxation of the heart as it fills with blood for the next contraction/beat, this actually doesn't increases as much as systolic blood pressure.
Thermoregulation - The definition of thermoregulation is "this is the maintenance of the internal body temperature independent from the environmental temperature". Another response on the cardiovascular system to steady state exercise of a runner would be the increase of thermoregulation. This happens due to the increase of the plasma volume, this supports the sweat glands during heat stress during steady state exercise. This actually maintains the correct amount of plasma to support and sustain the demands of the exercise. An untrained athlete is more than likely to heat up and sweat a lot faster during steady state exercise than a professional trained athlete, this is due to the fact that the athlete is able to sustain a lower core temperature and is able to reach a thermal steady state sooner than an untrained athlete. The reason why thermoregulation takes place is because of all the muscles during the exercise are working constantly, heating up the skin causing a human to sweat, this actually helps the bod cool down the body, by sitting on the surface of the skin and allowing any heat that is building up escape from the body. Sweat is also known as the evaporation process of thermoregulation and is where the water leaves our body in a vapour form.
Venous return - the definition of venous return is "this is the rate of blood flow back to the heart, it normally limits cardiac output". Another response on the cardiovascular system to steady state exercise of a runner would be the increase of venous return. The venous return must equal to the cardiac output because the cardiovascular system especially works in a closed loop. Venous return is where the veins actually solve any problems related to the low blood pressure of venous blood, venous blood is the blood that is found within the veins, and is deoxygenated blood in the circulatory system. Venous return the where the valves which are found within the veins, allow a one way flow of blood back towards the heart, this is so that the deoxygenated blood would return to the heart in order to get oxygenated again. Muscular contractions during steady state exercise actually aid venous return in cases of low blood pressure, veins can do a similar process by compressing themselves.
Starlings Law - The definition of starling's law is "This is a law created by Frank Starling, and is the law of the heart. He states that the greater the volume of blood entering the heart during diastole, the greater the volume of blood ejected during systolic contraction". Another response on the cardiovascular system to steady state exercise of a runner would be the starling's law. The starling's law tries to suggest that the stroke volume increases, this is in response to the increase of the blood volume filling the heart. Cardiac muscles contract more forcefully because of the ventricular wall stretches. Cardiac muscle actually contract greater resulting in a greater increase of stroke volume. This law actually suggest that a trained athlete has a more reduced heart rate when in steady state exercise, this allows greater filling during the longer diastole blood pressure, and this means that the stretch of the cardiac muscle is greater. This helps the increases of stroke volume.
Summery of the responses of the cardiovascular system during steady state exercise.
The cardiovascular system has 8 different responses to steady state exercise, this can affect the performance of the running athlete in different ways, whilst in steady state exercises, your heart rate starts to rise before exercise due to the anticipation, and this is known as the anticipatory response. During steady state exercise, the heart works faster and harder in order to pump oxygenated blood around the body to the working muscles. In process to this the stroke volume actually increases, this is the amount of blood pumped out of the left ventricle, and allows the heart to pump more blood around the body. Both of these result in an increase of cardiac output. Vascular return occurs during this process, returning deoxygenated blood back to the heart so that it can re-oxygenate and thus the heart pumping it back out towards the working muscles. During steady state exercise, thermoregulation increases, which allow the athlete to sweat, it also allows him to sustain internal core temperature throughout the exercise. The blood flow increases due to the vasodilation of the blood vessels, however it can decrease due to vasoconstriction which is the decrease of diameter of the blood vessels, this can increases blood pressure. Blood pressure increases because of the dilation of the blood vessels and mainly because of the muscles and the heart contract faster and harder, resulting in more pressure against the bodies arteries. A theory that suggests how the heart works is the Frank Starling's law which suggest that the more blood that fills the heart during the diastole stage, results in the more blood pumped out of the heart during the systolic stage, this can result into an increase of heart rate and stroke volume.
Another system that is used during steady state exercise would be the respiratory system;