It is well known that during exercise, the human body uses energy to produce movement and
work at a higher-than-normal intensity. This energy expenditure aids in weight loss, promotes muscle growth, and is probably the reason most people work out to begin with. However, the energy expenditure that the body experiences both before and after exercise is also important to consider in everyday life.
Resting Metabolic Rate
An individual’s resting metabolic rate, or RMR, is the energy that is required to keep their body functioning at rest (2). Excess post-exercise oxygen consumption, or EPOC, describes the heightened metabolic activity that happens for some time after an exercise session (1). By understanding both of these concepts and the factors that play into them, you can take the necessary actions in your everyday life to allow your body to work just as hard for you at rest as you do in the gym.
RMR, as previously stated, in the energy that is required to keep the body functioning at rest.
This rate supports organ functionality, breathing, blood circulation, and basic neurological activity, and it also accounts for ~60- 75% of the total daily energy expenditure for the average sedentary person (1, 2).
A higher RMR means more energy is burned while in a resting state, which is ideally what most people want. There are several factors that can influence an individual’s RMR. Fat free mass (FFM), which essentially is everything in the body other than fat (i.e. muscle, bone, etc.) has been found to be a large determinant of RMR; a higher FFM percentage = a higher RMR (4). Thus, if you want to increase your RMR, good habits to incorporate into your daily life would include eating adequate amounts of protein, resistance training, aerobic activities; things that are going to increase muscle mass and decrease fat mass.
Gender and RMR
Gender can also have an impact on RMR, as women tend to have lower FFM and a higher fat mass than men, resulting in a lower RMR (4). Therefore, women may have to work a bit harder to burn more energy at rest than men. Aging often shows a decrease in an individual’s RMR, due to the fact that people typically exercise less as they get older, which leads to an increase in fat mass and decrease in muscle mass (4). Knowing RMR can help individuals understand a lot about what exactly their body needs energy-wise to function and can also aid in weight loss or reaching specific fitness or health goals.
Excess Post-Exercise Oxygen Consumption
It can also give a key look into one’s current health levels, seeing as a higher RMR results in more energy being burned at rest and is typically seen in healthier individuals. Excess post-exercise oxygen consumption, or EPOC, refers to the elevated levels of oxygen uptake after the end of an exercise session (1). When you are working out, your body experiences a disturbance of homeostasis. There is an increase in temperature, blood lactate levels, O2 requirement, cardiorespiratory work, and levels of epinephrine and norepinephrine (1, 3). When you stop exercising, these levels do not just suddenly fall back to the resting-state values that they were in before the exercise. There is first a rapid decline over several minutes, and is then followed by a slower, more steadily-paced recovery (1). This process in itself burns energy, as your body is working to return to its normal resting state.
Studies have shown that the higher the intensity is during a workout, the more the energy that is required to return it to its normal, resting/recovery state (3). Thus, you can increase your body’s EPOC after a workout by increasing the intensity of each workout. To summarize, RMR can be altered by a number of factors, including exercise, FFM, age, and gender. It can also give a clue as to where a person’s health and fitness levels may fall and can aid in diet/exercise plans.
When examining EPOC and the conditions that increase it, it becomes apparent that the greater the disturbance of homeostasis in the body, the longer EPOC tends to take to return to a normal, resting state. The higher the intensity and duration of a workout, the longer EPOC is going to last. By considering the energy that is expended both before and after a workout, rather than just during, it can lead to an overall better understanding of the energy needs of the human body and can allow you to let your body work to its fullest potential.
References:
1. Powers SK and Howley ET. Exercise Physiology. 10th ed. New York: McGraw-Hill
Education; 2018.
2. Comana F, Penney S, Stone JJ, et al. Resting Metabolic Rate: How to Calculate and Improve
Yours. NASM Blog 2019; Available from: https://blog.nasm.org/nutrition/resting-metabolic-rate-
how-to-calculate-and-improve-yours/
3. Burleson MA, Obryant HS, Stone MH, Collins MA, Triplett-Mcbride T. Effect of weight
training exercise and treadmill exercise on post-exercise oxygen consumption. Medicine &Science in Sports & Exercise 1998;30(4):518–22.
4. Gilliat-Wimberly M, Manore MM, Woolf K, Swan PD, Carroll SS. Effects of Habitual
Physical Activity on the Resting Metabolic Rates and Body Compositions of Women Aged 35 to 50 Years. Journal of the American Dietetic Association 2001;101(10):1181–8.
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