How is the heat consumed by exercise calculated?

First of all, sports participants must understand that if the human body uses glucose as energy, it will produce 1 liter of carbon dioxide for every 1 liter of oxygen consumed, that is, the respiratory quotient (RQ) of glucose as energy is equal to1; RQ when fat is used as energy source is about equal to 0.7; When protein is used as the energy source, RQ is about 0.8. However, it is difficult to evaluate the respiratory state of tissues in human body. Therefore, by measuring the lung gas exchange state (respiratory exchange ratio, RER for short, the increase of carbon dioxide in lung gas exchange divided by oxygen consumption) when the human body participates in exercise, and protein only participates in providing energy in a small amount; Sports physiology researchers can evaluate the energy consumption characteristics of exercise process according to the gas exchange in the lungs.

Generally speaking, the RER of human body is about 0.82 at rest, but it will decrease (between 0.75 and 0.80) at very low intensity (walking, jogging and easy riding), and it is about 1 when approaching the maximum exercise. That is to say, in the state of low-intensity exercise, the proportion of fat participating in providing energy is high. With the increase of exercise intensity, RER also increases, and the proportion of glucose participating in providing energy also increases. In the state of maximum exercise, almost all of them are powered by glucose. When RER is equal to 0.85, glucose and fat each provide half of the energy needed by the body. In addition, with the rise of RER, the energy that the human body can produce for every 1 liter of oxygen consumed is also increasing. For example, when RER is equal to 0.8, the human body consumes 4.80 1kcal per liter of oxygen; When RER is equal to 0.9, every liter of oxygen consumed by human body can generate 4.924 kilocalories of energy; When RER is equal to 1, the human body consumes 5.047 kilocalories per liter of oxygen. Although the difference between the lowest energy and the highest energy is less than 1%, it is an indisputable fact that the energy consumption per kilogram of oxygen will gradually increase with the increase of exercise intensity.

The following examples can make you more clear about the evaluation of energy consumption during exercise. "If you went shopping by bike for 30 minutes yesterday, the exercise intensity was 5METs (that is, the oxygen intake intensity was 5×3.5ml/kg/min), and the average respiratory exchange rate during exercise was 0.9, then how many grams of glucose and fat did you * * * consume during the 30 minutes of cycling? 」。

First of all, you have to determine how many kilograms you weigh. If your weight is exactly 70 kg, then the total oxygen consumption in 30 minutes is 5× 3.5ml/kg/min× 70kg× 30min = 36,750ml oxygen, * * * oxygen consumption is 4.924kcal/l× 36.75l =180.96kcal energy (excessive oxygen consumption after exercise is not.

Without considering the slow decline of heart rate and oxygen consumption after exercise, the energy consumption during 30 minutes of moderate intensity cycling exercise is about 180kcal. If protein doesn't provide the body energy source during exercise (only glucose and fat provide energy), then a RER of 0.9 means that fat accounts for one-third of the body energy source and glucose accounts for two-thirds (0.7×1/3+/kloc-0 /× 2/3 = 0.9). That is to say, of the energy consumption of 180kcal, one third (60kcal) is provided by fat and two thirds (120kcal) by glucose. Since each gram of fat in the human body can provide about 9 kilocalories, each gram of glucose can provide about 4 kilocalories. Therefore, in 30 minutes of cycling, you can consume about 6.7 grams (60/9) of fat and 30 grams (120/4) of glucose.

If the participants do low-intensity exercise (for example, the intensity of 4 meters), the exercise time can be easily increased (for example, the exercise time can be increased to 37.5 minutes); Coupled with the decrease of exercise intensity, the average RER during exercise decreases (assuming it decreases to 0.85); At this time, the energy consumption within 37.5 minutes of exercise is still about180 kcal (4× 3.5 ml/kg/min× 70 kg× 37.5 min = 36,750 ml). Because the RER of 0.85 means that the energy provided by fat and glucose accounts for half of the body's energy source (0.7×1/2+/kloc-0 /×1/2 = 0.85). Therefore, in a 37.5-minute exercise, you can consume about 65,438+00g (90/9) of fat and 22.5g (90/4) of glucose (although the energy generated per liter of oxygen is about 4.862kcal when RER=0.85, 36.75 liters of oxygen consumption can still consume about 65,438).

Although the energy consumption during exercise can be evaluated by simple calculation, ordinary people still need to know that both oxygen consumption and carbon dioxide production need to be measured by special instruments in order to build a correct energy consumption calculation basis. If you increase

Judging from the energy consumption and fat burning during exercise, it seems that the exercise participation mode with slightly lower intensity and longer time is better.

I hope this answer is helpful to you.