Oxygen is key to calorie burning because it is an essential ingredient in the breakdown of carbohydrates and fat into energy for your muscles. Increasing the rate of oxygen consumption, by doing activities that raise your heart rate, helps you convert more energy, helping your body use up all those unwanted calories. Your VO2 rate tells you just how much oxygen you are getting.
The rate of VO2 can vary greatly depending upon gender, age, fitness level and genetic predisposition. Measuring your VO2 with complete accuracy requires expensive machinery and testing.
An average, healthy year-old male should have a VO2 max of 2. An athlete's VO2 max would be higher. If you are just starting out with exercise, your VO2 rate may be lower, but will increase with improved athleticism. In general, you can assume an average VO2 of 3 liters of oxygen a minute.
If you know your VO2 rate, you can use your heart rate to approximate how much oxygen your activity is causing you to consume. Knowing this, you can estimate how many calories you are burning. This method provides an approximation of the V02 max from the maximum distance that the subject can run in 12 minutes.
The Heart Rate Reserve method takes the resting heart rate into account and can also be used in concert with the VO2 max to monitor exercise intensity according to ExRx. Read more: Cardio Exercise Heart Rate. A person wishing to estimate their calorie expenditure rate wears a chest strap that monitors the heart rate. You can also track your heart rate and calorie expenditure with a wearable if you have one, says Mayo Clinic.
The heart rate monitor must be capable of recording the average heart rate and time of the exercise session. The person performs an aerobic activity such as running, walking or cycling and begins recording the heart rate once it reaches 90 bpm. At this point, nothing else needs to be done except to ensure the heart rate doesn't exceed bpm.
The heart rate may continue to be recorded after the exercise session is concluded until the heart rate drops to 90 bpm. The correct formula may be used to estimate calorie expenditure once the required data has been gathered.
This consists of the VO2 max if available , average heart rate, time of exercise, age, weight and gender. The VO2 max should be evaluated periodically since it can change over time, especially when a person begins exercising regularly. Fitness Training Heart Rate Information.
You the fitness professional should be aware of what determines how many calories your body burns during exercise, why your body obeys certain rules that dictate the magnitude of caloric expenditure, and what are the best types of exercises that increase caloric expenditure.
With this knowledge you can effectively educate your clients to more realistic goals that may be accomplished with your exercise prescription. In addition, you can better explain to your clients the truth about many of the advertising claims that suggest a particular exercise modality is best for caloric expenditure and weight loss. We will begin with a brief discussion on the relationship between aerobic exercise, caloric expenditure, and exercise intensity. We will then present data from a laboratory case study we conducted to compare cardiorespiratory responses and caloric expenditure during cycle ergometry, arm ergometry, and combined leg and arm ergometry.
The results presented will be combined with the published research on this topic to clearly illustrate the interrelation between exercise intensity, lower and upper body exercise, and caloric expenditure.
What determines caloric expenditure during exercise? At rest, your body expends energy to maintain the functions of cells that are essential for life. The continual pumping of blood by the heart demands energy, as does the continual ventilation movement of air into and out of the lungs. In addition, maintaining a life supporting environment within and around cells requires a constant breakdown of certain energy releasing molecules.
This energy is also used to form the molecules necessary for repairing cells, storing energy glycogen and triglycerides , fighting infection, and processing nutrients obtained from digestion. These energy demanding functions combine to form the body's basal metabolic rate, which can vary from approximately to Kcals depending upon body size and total caloric intake ingested quantity of food.
Adenosine triphosphate ATP is the main molecule the body uses as a means to use chemical energy to perform cellular work. Exercise adds to the caloric expenditure of the body, as muscle contraction involves the need to repeatedly form and breakdown ATP. The energy released from the breakdown of ATP fuels the contraction of skeletal muscle, thereby adding to the energy demands of the body and raising caloric expenditure.
Research has shown that during exercise the increase in caloric expenditure is almost entirely due to the contraction of skeletal muscle; the balance is due to an increase in the energy demands of the heart and the muscles used during ventilation. How is caloric expenditure measured? Caloric expenditure can be measured directly, which requires the measurement of the heat released by the body, or indirectly be measuring ventilation and the exchange of oxygen and carbon dioxide by the body.
These methods are termed direct calorimetry and indirect calorimetry, respectively, and the research and validation of these methods date back to the late 's Lusk, For numerous methodological reasons, the method of indirect calorimetry is the most suitable and accurate to evaluate caloric expenditure during exercise. When a person expends calories, the body uses oxygen and produces carbon dioxide.
Not all bodily reactions consume oxygen and produce carbon dioxide, but without the reactions that do, the remaining reactions of the cells would eventually stop, and the cells would die. This fact is important, as it means that quantifying the consumption of oxygen and production of carbon dioxide is an indirect means to measure the calories that are released and used by the reactions of the body. All that we need to know is the relationship between oxygen consumption and caloric expenditure.
Fortunately, scientists who studied calorimetry during the first two decades of the 19th century determined this relationship for us Lusk, The number of calories released from the consumption of oxygen during cellular metabolism differs slightly when carbohydrate, fat, or protein are the nutrient source.
However, as the body predominantly uses carbohydrate and fat as the nutrient sources, or "energy substrates," we only need to focus on these substrates. The energy released from carbohydrate and fat within the body approximates 4. Thus, fat is a more dense source of energy than carbohydrate. However, remember that we are not concerned with the amount of energy available from a given amount of energy substrate, but with how much energy is available relative to oxygen consumption.
For pure carbohydrate and fat catabolism breakdown , these caloric amounts are actually 5. Therefore, the difference in caloric expenditure between pure carbohydrate and fat catabolism, of an average healthy person exercising for 30 min at a VO2 oxygen consumption of 1. This is a small difference, but indicates that for accurate calculations of caloric expenditure during exercise, there is a need to know how much carbohydrate and fat are being used as energy substrates.
The contribution of carbohydrate and fat to energy metabolism the process of chemical changes to provide energy can be determined from the ratio between carbon dioxide production and oxygen consumption. This is referred to as the RER, or respiratory exchange ratio of carbon dioxide to oxygen consumption. The metabolic basis for this relationship lies in that there is greater carbon dioxide production from carbohydrate catabolism compared to fat catabolism.
Thus, the lower the carbon dioxide production relative to oxygen consumption, the greater the contribution of fat catabolism to caloric expenditure. We are now armed with the academic knowledge needed to understand exercise intensity. In this article, our focus is exercise intensity and caloric expenditure.
We will not elaborate on how one can maximize either carbohydrate or fat catabolism during exercise. We will save that topic for another article in another issue. What are valid methods for estimating exercise intensity? From the information thus far presented, it should be clear that the best measure of the change in metabolism during exercise is oxygen consumption.
As one completes the transition from rest to exercise, there is often an exponential increase to a plateau in oxygen consumption until a steady rate is attained, termed steady state.
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