Basic physiology of resistance exercise (III)

The cardiovascular system is the system par excellence that no one doubtlessly associates with endurance activities. Being important, it does not have more stripes than the other systems, since without the interaction of all of them it could not do anything by itself.

This system is the one that guarantees the supply of oxygen to the organism so that all the necessary chemical reactions take place to degrade the energy substrates, convert them into mechanical energy and subsequently eliminate the resulting residues.

The indicator par excellence of the capacity of the cardiovascular system is the maximum oxygen consumption or the well-known acronym VO2 max. This value is nothing more than our body’s ability to capture oxygen from the environment and use it in cellular reactions to transform it into movement. The greater this capacity, the greater the performance capacity of the individual.

The value of oxygen consumption varies between 20 ml/min/Kg up to 90 in professional elite athletes. The athletes with a higher value with respect to their body weight are cross-country skiers. The athletes with a higher absolute value are rowers. It is important to understand the difference between the relative and absolute concept.

Oxygen consumption is a performance value that is highly determined by genetics. With training you can improve a lot although it is still not very clear in what percentage. Some authors speak of a demoralizing 10-15% while others dare to ensure that 50%.

It is worth asking why there are individuals with a higher value of VO2 max. The reasons have to do with the cardiovascular and muscular system. These are:

Blood saturation and capacity

Saturation and capacity determine the amount of oxygen that can be transported from the lungs to the muscles. That is, the amount of red blood cells that we have in the blood and the percentage of them that carry oxygen to take it to the muscles. The more red blood cells, the greater the capacity and the more % of them charged, the greater the saturation.

The capacity is limited by the amount of carriers (red blood cells) in a given volume of blood. It may be the case that there is a lot of saturation but little oxygen transport and vice versa. Both cases are worrying, since the first indicates low levels of red blood cells and in the second case, respiratory failure.

The saturation of the blood may be conditioned by a disease that causes respiratory failure and the altitude at which we find ourselves, among other causes. Maximum intensity physical activity can also cause a reduction in saturation levels. The cause? The red blood cells pass so quickly through the capillaries of the lungs where they have to load the oxygen that they do not have time to do so and they go empty with the consequent loss of ventilatory contribution.

Cardiac peak flow

The second factor is the amount of blood that the heart sends to the organs per minute. For its calculation, the volume of blood sent in a heartbeat is multiplied by the beats per minute that an athlete reaches. The more flow, the greater the possibility of oxygenation and therefore a greater possibility of having a high VO2 max .

One might think that a larger heart and a greater number of beats ensure a greater flow, and this is not necessarily so. The heart takes time to fill with blood before ejecting it. If the heart beats too fast, it does not have time to fill up and therefore, the flow decreases despite having increased the frequency of the heartbeats. Our organism is so incredibly efficient that it regulates the beats by optimal minutes to be able to send the maximum cardiac flow.

Muscle utilization

Finally, and thirdly, once the oxygenated blood reaches the muscle cell, which is the one that must “stretch” the oxygen molecule of the red blood cells to take advantage of it in their energy-extracting metabolic reactions . An increase in the capillarization of the muscle and the capacity of the mitochondria within the muscle fiber, thanks to training, allows this to be possible and the reverse situation does not occur than in the lungs with the desaturation of the blood due to the high speed of circulation. That is to say, that the red blood cells return to the lungs loaded with O2 because they have not had time to discharge it where they should.

In stress tests with direct gas analysis, the VO2 max of athletes can be accurately determined and therefore classified in order from highest to lowest.

However, this classification does not have to be the same as that of any competition with a bib number. Ignoring the technical conditions that make an athlete more or less efficient when it comes to using their physical resources, not only VO2 max determines the athlete’s final classification. Therefore, it can be stated emphatically that with equal technical level and physical inferiority with a lower VO2 max you can beat another competitor.

The VO2 max is still a specific performance level that can be sustained for a limited period of time (about 10-15 minutes). In competition, and the longer it is, the more important it is, what determines the final performance is no longer so much this speed but the average speed that can be sustained throughout the race. It is obvious that with higher VO2 max values we will have a higher ceiling to obtain a higher average, but that is not all about it.

In the stress tests, apart from the VO2 max that classifies us (and demoralizes us in many cases) they give us the intensity values corresponding to the aerobic and anaerobic thresholds. The intensity level of the anaerobic threshold is actually what will allow us to sustain the average speed of the race. The more well trained an athlete is, the greater proportion of VO2 can be used to sustain his speed.

From this conclusion it can be deduced the great importance of having good genetics, but we should never underestimate the daily work in training, since they will offer us the possibility of squeezing our motor.

On the other hand, the longer the races, the less influence this value has and the greater influence aspects of efficiency and competition management have. If one trains to achieve his maximum potential and plays his cards correctly, he can still enjoy the races and reach the finish line with even greater satisfaction than someone who has been touched by the gods and has plenty of horses.