What Is Cardiac Output?
Cardiac output refers to the amount of blood pumped out per ventricle each minute. It is measured in liters per minute. It is calculated as the product of heart rate and stroke volume. Heart rate is the number of times the heart beats in a minute, and stroke volume is the volume of blood pumped out by the ventricle during one contraction.
The cardiac output of a healthy person during rest is around 5-6 L/minute of blood. It may rise to 3 to 4 times more than normal when the intensity of physical exercise increases, and as a result, the oxygen requirement by your muscles increases. It rises to more than 35 L/min in trained athletes during exercise.
An optimal cardiac output is needed for a continuous supply of oxygen and nutrients to all the organs.
Cardiac Output and Exercise
During exercise, as you exert yourself, your muscles need more oxygen. The demand for blood supply increases. Your heart beats faster to pump more oxygen-rich blood to the muscles. When this happens, more volume of blood is pumped out from the heart. An increase in heart rate and stroke volume leads to an increase in cardiac output during exercise.
When you exercise, more blood is pumped into your muscles. As your body temperature increases, more blood is pumped into the skin also. This happens because of increased cardiac output and redistribution of blood flow.
Optimal cardiac output maintains blood pressure at a desirable level to supply sufficient amounts of oxygen-rich blood to all the vital organs in the body.
As the intensity of exercise increases, the cardiac output also increases till you reach a point of exhaustion.
How Does Genetics Influence Cardiac Output?
ADRB2 Gene
The ADRB2 gene encodes for the beta-adrenergic receptor protein. It binds to epinephrine and mediates physiologic responses that include relaxation of smooth muscle, heart muscle contraction.
Several SNPs in this gene are associated with cardiovascular regulation during rest and exercise and with the progression of cardiovascular diseases.
*rs1042713 *
rs1042713 is an SNP in the ADRB2 gene. People carrying the GG genotype are found to have an increased value of cardiac output during rest and exercise compared to the other two genotypes.
Non-Genetic Factors That Affect Cardiac Output
- Hormones: As a response to danger or stress, hormones such as epinephrine and norepinephrine are released. These increase the heart rate and contractions of the heart, thereby increasing cardiac output.
- Health conditions: Health conditions such as hypertension and other cardiovascular problems affect cardiac output.
- Changes in body temperature: Heart rate increases with increase in temperature. This results in increased cardiac output.
- Sex: Women are found to have a higher heart rate than men.
- Age: The heart rate and pumping capacity reduces with age.
Increasing Your Cardiac Output
- Working out consistently trains your body and heart and keeps your heart healthy.
- Mix up your workout. Try out exercises of various intensity to improve your recovery after exercise.
- Increasing the intensity of exercise gradually. Sudden excess physical exertion to the heart is not recommended. Let your heart get used to the increase in the intensity of exercise.
- If you feel any abnormal strain on exercising, talk to a healthcare professional to treat the underlying cause.
- Eat a balanced diet focused on maintaining heart health.
Summary
- Cardiac output refers to the amount of blood pumped out per ventricle every minute. It is calculated as the product of heart rate and stroke volume. The optimal resting cardiac output is around 5-6 L/minute of blood.
- When you exercise, the oxygen demand increases and more blood is required to be pumped to the muscles and skin. Cardiac output increases up to 3-4 times than normal during exercise.
- Variations in certain genes are found to affect the metabolic rate. The A allele of the ADRB2 gene is associated with lower cardiac output during rest and exercise compared to the GG genotype.
- Certain health conditions, cardiac output, changes in body temperature, sex, and age can influence cardiac output.
- Following a proper exercise routine, balanced diet can help you maintain optimal levels of cardiac output and keep your heart healthy. Increase the intensity of exercise gradually.
References
https://www.ncbi.nlm.nih.gov/books/NBK470455/
https://www.webmd.com/heart/heart-cardiac-output
https://pubmed.ncbi.nlm.nih.gov/23438238/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3076691/
