This week, Janis Newton, the director of the Medical University of South Carolina's Wellness Center, discusses the connection between heart rate and metabolism.
Question: I've heard that the more I work out or get in shape, the slower my heart rate becomes. But wouldn't this mean a slower metabolism and ability to burn calories as well?
Answer: Improved cardiovascular fitness usually does result in a lower resting heart rate, which means that your heart is more efficient at transporting oxygenated blood throughout your body.
Therefore, having a lower resting heart rate is beneficial to your heart health.
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The average resting heart rate ranges from 60 to 80 beats per minute, although well-trained athletes sometimes have a resting heart rate as low as 40 beats per minute.
Metabolism refers to the body's process of converting caloric intake into energy so the body can successfully carry out various physiological functions.
About 70 percent of a human's metabolic rate is the result of basic functions of the body such as breathing, blood circulation, maintenance of body temperature and growing and repairing cells. About 20 percent of energy expenditure comes from daily physical activity and another 10 percent from digestion of food (thermogenesis).
An increased heart rate does increase metabolism since there is a greater demand on the body such as supplying glucose for working muscles. When resting, your metabolism will be lower since it doesn't take as much energy to maintain a resting state.
However, remember, at rest, around 70 percent of the metabolic process still comes from the maintenance of basic body functions regardless of physical activity and heart rate. Only 20 percent is affected by the difference in physical activity versus rest.
This means that your metabolism is not dependent on your heart rate to be efficient. Even though an increase in heart rate does stimulate the metabolism, the metabolic process is still stimulated by other demands after the heart rate returns to normal.
Heart rate does not equal metabolic rate. People with higher metabolisms do not necessarily have higher resting heart rates and vice versa. Metabolism is also affected by gender, age, weight, body fat percentage, diet and exercise.
The important message to remember regarding resting heart rate and metabolism:
When you exercise regularly and increase your heart rate, your heart is strengthened. When you are at rest, the strengthened heart doesn't need to do as much work. This means it can pump oxygenated blood efficiently around your body at a lower heart rate. The health benefit of a lower resting heart rate is that you are at less risk of heart disease.
Muscle is the biggest contributor to our metabolic rate and we lose muscle mass as we age. Our energy needs decrease as we lose muscle mass. It is important to do activities such as strength training to keep healthy muscle mass and a healthy metabolism.
Diet can also affect our metabolic rate. When we restrict calories too much our metabolism can slow up to 30 percent! It is important to eat healthy foods throughout the day and fuel our body effectively. Everything we eat and drink will either fight a disease or feed a disease.
Metabolism can only be boosted in two ways: increasing the body's muscle mass and increasing the body's heart rate.
Your metabolic rate depends on many factors, according to www.mayoclinic.com, including genetics, body type, gender, age, hormones, diet and exercise.
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