Breathing in sports exercise

2021-06-10 03:26 PM

There is a linear relationship. Both oxygen consumption and total pulmonary ventilation are approximately 20-fold increased from resting-state and maximal exercise intensity in well-trained athletes.

Although a person's respiratory capacity is of little importance for sprint performance, it is crucial for maximum performance in endurance running.

Oxygen consumption and pulmonary ventilation during exercise. Normal oxygen consumption for a young man at rest is about 250 ml/min. However, under maximum conditions, this consumption can be increased to an approximate average of the following:

 

ml/min

Average in men who don't exercise

3600

Male soldiers practice sports

4000

Running men's marathon

5100

Figure. Effect of exercise on O2 consumption and ventilation rate.

The figure shows the relationship between oxygen consumption and lung ventilation at different levels of exercise.

As expected, there is a linear relationship. Both oxygen consumption and total pulmonary ventilation are approximately 20-fold increased from resting-state and maximal exercise intensity in well-trained athletes.

Limits of pulmonary ventilation. How about emphasizing our respiratory system during exercise?

This question can be answered by the following comparison of a young man:

 

L/min

Pulmonary ventilation during maximal exercise

100-110

Maximum breathability

150-170

Thus, maximal expiratory capacity is approximately 50% greater than actual pulmonary ventilation during maximal exercise. This distinction provides an element of safety for athletes, providing them with additional ventilation under conditions such as (1) exercising at altitude, (2) exercising in very hot conditions, and (3) abnormalities in the respiratory system.

The important point is that the respiratory system is not usually the most limiting factor in delivering oxygen to the muscles during maximal aerobic metabolism. We will soon see that the heart's ability to pump blood to the muscles is often a larger limiting factor.

Effect of exercise on VO2 max

The abbreviation for the rate of oxygen utilization in maximum aerobic metabolism is VO2 max. Figure showing the progressive effect of athletic training on VO2max recorded in a group of subjects starting at the level of no training and then while pursuing training programs for 7-13 weeks. In this study, surprisingly, VO2max only increased by about 10%.

Furthermore, exercise frequency, whether twice or five times per week had little effect on VO2max gains. However, as pointed out above, the VO2max of a marathon runner is about 45% greater than that of an untrained person. A greater part of this VO2max of marathon runners can be determined by genes; that is, people with larger chest size relative to their body size and stronger respiratory muscles to choose them to become marathon runners.

However, it is also possible that years of training increase a marathoner's VO2max by a significant amount of more than 10% that has been observed in short-term experiments as shown in Fig.

Figure. Increase VO2max during 7 to 13 weeks of exercise.

Oxygen diffusion capacity of athletes

Oxygen diffusion capacity is the rate at which oxygen can diffuse from the alveoli into the blood. This capacity is expressed as the number of millilitres of oxygen that will diffuse in one minute for each millimetre of mercury that differs between the alveolar partial pressure of oxygen and the pulmonary arterial blood oxygen pressure. That is, if the partial oxygen pressure in the alveoli is 91 mmHg and the oxygen pressure in the blood is 90 mm Hg, the amount of oxygen that diffuses across the respiratory cell membranes per minute is equivalent to the diffusion capacity. The following values ​​are measured for different diffusivity values:

 

ml/min

Not being an athlete at rest

23

Not being an athlete at maximum training

48

Figure skater at maximum training

64

Athletes swim at maximum exercise

71

Athletes rowing at maximum training

80

The most surprising fact about these results is the severalfold increase in the distribution capacity between the resting state and the maximal exercise state. The finding of this result is mainly from the fact that blood flow through many pulmonary capillaries is sluggish or even inactive at rest, whereas during maximal exercise the increased blood flow through the lungs causes all Both pulmonary capillaries are maximally perfused, thus providing a larger surface area through which oxygen can diffuse into the pulmonary capillary blood.

It is also clear from these values ​​that athletes, who require a greater amount of oxygen per minute, have a higher diffusion capacity. Is this the case because people with greater natural diffusivity choose sports, or is it because something in the training routine increases diffusion? The answer is no, but it's likely that training, especially endurance training, plays an important role.

Blood gas in training

Because of the large amount of oxygen used by the muscles during exercise, the oxygen pressure of the arterial blood is markedly reduced during intense sports, and the carbon dioxide pressure in the venous blood is too high compared to normal. However, this is usually not a problem. Both of those values ​​are still close to normal, demonstrating the respiratory system's amazing ability to provide adequate oxygen in the blood even during intense exercise.

This proves an important point: blood gases do not always become abnormal when respiration is stimulated during exercise. Instead, respiratory stimulation is primarily neurogenic during exercise. Part of this stimulation results from direct stimulation of the respiratory centre by the same nerve signals that are transmitted from the brain to the muscles for exercise. Another part is thought to result from sensory signals transmitted to the respiratory centre from muscles contracting and moving joints. All of this extra nerve stimulation is usually enough to provide almost exactly the necessary increase in pulmonary ventilation needed to keep the gas—respiratory blood oxygen and carbon dioxide—very close to normal.

Effect of smoking on pulmonary ventilation during exercise

It is widely known that smoking can depress an athlete's ventilation. This is true for many reasons. First, the effect of nicotine constricts the bronchioles in the lungs, increasing the resistance of the lungs to the flow of air in and out. Second, the irritating effects of cigarette smoke cause increased secretion of fluid into the bronchial tree as well as oedema of the epithelial lining. Third, nicotine paralyzes the epithelial cell cilia on the surface of the respiratory tract, which are normally in constant motion to remove excess fluid and foreign particles from the airways. As a result, more debris accumulates in the airways and adds to the difficulty of breathing.

After taking all these factors together, even a light smoker often experiences respiratory discomfort during maximal exercise, and activity levels can be reduced. More serious are the effects of prolonged smoking. There are very few long-term smokers whose degree of emphysema does not develop. In this disease, the following mechanisms occur (1) chronic bronchitis, (2) obstruction of many of the terminal bronchioles and (3) destruction of many alveolar walls. In people with severe emphysema, four-fifths of the cell membranes of the airways may be destroyed; then even light exercise can cause respiratory failure. In fact, many such patients may not even perform the simple feature of walking on the floor in a single room without panting.