Stroke volume is able to increase for two reasons:
- Increased venous return – this is the volume of blood that returns from the body to the right side of the heart.
- The frank starling mechanism
Cardiac output is the volume of blood pumped out of the heart per minute and is the product of stroke volume and heart rate. Therefore when the heart rate and stroke volume increases results in the cardiac output increasing. The cardiac output will continue to increase until the maximum level of exercise if being carried out.
Blood pressure increases depending on the intensity of exercise being carried out. During steady aerobic exercise involving large muscle groups the systolic pressure increases, while diastolic pressure remains constant or in well trained athletes it may drop.
Systolic pressure increases when a greater intensity is carried out this is so the right amount of blood is delivered to the working muscles quickly. During high intensity exercise both systolic and diastolic pressure rise due to increased resistance of blood vessels. This is cause by muscles squeezing veins.
Blood flow changes once exercise is taking place. During exercise the blood flow is changed from being directed at the liver and kidneys to the most needed areas. This is because the working muscles need more oxygen so more blood is needed to meet this demand. So this demand can be met and the muscles and keep working efficiently at a high impact the blood is redirected from the liver, kidneys, and digestive system to the muscles that are in demand of oxygen.
The long-term effects are:
- Decrease in blood pressure///
- Hypertrophy of the heart
- Increase in thickness of the myocardium
- Increase in stroke volume at rest
- Increase in cardiac output
- Decrease in resting heart rate
Cardiac hypertrophy is the enlargement of the heart. Hypertrophy, of the heart muscle occurs due to increased stress on the heart. The extra work of pumping blood against the increased pressure causes the ventricle to thicken over time, the same way a body muscle increases such as an athlete continuously working his legs his leg muscles will become bigger.
The myocardium increases in thickness due to hypertrophy. This is because the heart is being forced to work harder and more regularly. As it grows stronger it is able to meet the required demands with ease as well as at a quicker pase.
Stroke volume at rest decreases if regular exercise takes place. The heart becomes bigger meaning it can hold a larger volume of blood. Because the heart can hold a larger amount of blood it means it can also pump out a larger volume in a single circuit decreasing the stroke volume.
Bradycardia is defined in adults as a pulse rate below 40 beats per minute. If this occurs the patient is usually put on medication to help solve this problem. This often occurs in elite athletes due to hypertrophy of the heart and the increase in stroke volume there hearts are so efficient they do not need to beat any faster as there bodies are efficient enough to deal with only 40bpm.
Cardiac output is increased due to a larger volume of blood therefore the heart doesn’t have to work as hard as it did before and the cardiac output is then decreased.
Resting heart rate is effected by exercise because the muscles in the body demand more oxygen. This means the heart needs to work harder to ensure enough oxygen is delivered to the blood so the oxygen can be carried to the working muscles and the carbon dioxide and lactic acid are removed. Therefore the more you exercise the stronger the heart will become and won’t have to work as hard when it is at rest lowering the resting heart rate.
Therefore the resting heart rate is decreased and it is not necessary for the heart to beat as quick as it did, now the heart is larger it can beat slower but still achieve pumping the same amount of blood.
