Effects of training on the circulatory system
The cardiovascular response to exercise has intrigued physiologists for many years and has led to a great effort to unravel the mechanisms of circulation changes as well as the role of the nervous system adjustments in various intensities of work.
During exercise, the muscles that are contracting require a continual supply of nutrients and oxygen to support energy production. These requirements are over and above those required to support normal activities at work or rest. As a result, the heart has to beat harder and faster to meet these increased demands. If these demands are repeated frequently as a result of a systematic training program, over time the heart becomes stronger. The heart and blood vessels of the circulatory system adapt to repeated bouts of exercise.
The exact amount of change will depend on the intensity (low or hard) and duration (how long)of the exercise.
The following changes will take place within the cardiovascular system during exercise.
SHORT-TERM CARDIOVASCULAR RESPONSES TO EXERCISE
Anticipatory heart rate
Nerves that directly supply the heart and chemicals within the blood can rapidly alter heart rate. Before starting exercise your pre-exercise heart rate usually increases above resting levels. This is known as anticipatory heart rate. Yes, your heart rate will likely increase before you even begin moving! The greatest anticipatory heart rate response is observed in short sprint events. Therefore, the anticipatory increase can depend on an athlete’s emotional state, often belying his or her true resting state. This causes heart rate to rise rapidly in anticipation of exercise.
Heat production
There is an increase in body temperature and heat is produced. As a result, you sweat to help keep the body temperature stable.
Skin color
The blood vessels at the surface of the skin have to open up to allow the heat to escape and this can cause a flushed or reddening effect, often seen on the face.
Heart rate at onset of exercise
This is the heart rate as exercise commences.
At rest, a normal adult heart beats approximately 75 beats per minute, peaking at around 200 beats per minute for strenuous activity, but this figure depends on the person’s age.
Redirection of blood flow
At the start of exercise, or even slightly before, nerve centers in the brain detect cardiovascular activity. This results in adjustments that increase rate and pumping strength of the heart. At the same time, regional blood flow is altered in proportion to the intensity of the activity to be undertaken.
Blood pressure
This increases as more blood is circulated.
Blood pressure is the pressure of the blood against the walls of the arteries and results from two forces. One is created by the heart as it pumps blood into the arteries and through the circulatory system. The other is the force of the arteries as they resist the blood flow.
During exercise, although both cardiac output and blood pressure increase, these mechanism act to restrict the blood pressure rise and eventually bring it down to more efficient levels.
It is determined by two factors:
- The resistance offered by the vessel walls to the flow of blood. This can be dependent on several factors including blood vessel length and radius.
- Cardiac output or the volume of blood pumped out of the left ventricle in one minute.
Therefore, blood pressure is defined as: cardiac output x resistance. Blood pressure increases when either cardiac output or resistance increases.
Vasodilation
This is when the blood vessels widen in an attempt to increase blood flow.
Vasoconstriction
This is when the blood vessels constrict to reduce blood flow.
LONG-TERM EFFECTS OF TRAINING ON CARDIOVASCULAR SYSTEM
Cardiac hypertrophy
Cardiac hypertrophy is when the heart increases in size and blood volume. The wall of the left ventricle thickens, increasing the strength potential of its contractions. This has an important effect on stroke volume, heart rate and cardiac output.
Increased stroke volume
Stroke volume is the amount of blood pumped by one of the ventricles of the heart in one contraction (per beat). The stroke volume is not all of the blood contained in the left ventricle because the heart does not pump all the blood out. About two-thirds of the blood in the ventricle is normally put out with each beat. Stroke volume and heart rate together determine the cardiac output.
Stroke volume at rest has been shown to be significantly higher after a prolonged endurance training program. The heart can therefore pump more blood per minute, increasing cardiac output during maximal levels of exercise. Blood flow increases as a consequence of an increase in blood vessel size and number. This allows for more efficient delivery of oxygen and nutrients.
Increased cardiac output
Cardiac output is the volume of blood pumped out by the heart in one minute. It is equal to the heart rate multiplied by the stroke volume. If the heart beats 70 times a minute, and 70 ml of blood is pumped each time, the cardiac output is 4,900 ml per minute, or about 5 liters. This value is typical for an average adult at rest, although cardiac output may reach up to 30 liters per minute during extreme exercise.
During participation in sport and exercise, cardiac output is raised as a result of increases in either heart rate, stroke volume or both. Stroke volume does not increase significantly beyond the light work rates of low-intensity exercise, so the increases in cardiac output required for moderate- to high-intensity work rates are achieved by increases in heart rate. Maximum attainable cardiac output decreases with increasing age, largely as a result of a decrease in maximum heart rate. Maximum heart rate can be calculated using the formula below: maximum heart rate = 220 – age in years.
Decreased resting heart rate
This is when the resting heart rate falls, reducing the workload on the heart. Your heart rate returns to normal after exercise more quickly.
Closing thoughts: Effects of training on the circulatory system
Like any other muscle, the heart will respond to increased levels of exercise by improving its efficiency and pumping the blood around the body more effectively. It is important that you understand these changes as they will have a significant impact on your training and performance.
The impact of exercise on your heart rate can be a complex concept to understand. Your heart rate will definitely increase as your activity level rises, but there is a healthy range for your heart rate, and anything outside of that may be an indicator of a heart condition.
