Basic physiology of resistance exercise (II)

The energy and thermoregulatory system

2 de December de 2019

The energy system

Like any machine, if the body does not have an energy source, it is not capable of making any type of movement.

The human body has several ways to obtain energy depending on the type of exercise we perform, being able to overlap different energy substrates, so that there is never any cut in the supply that prevents maintaining continuity.

As an example, during the first meters of a long-distance race we would do what Usain Bolt did (ATP and PC anaerobically and without lactate generation); later we would use the fuel as a middle-distance runner (CH in an anaerobic way with lactate generation); and finally we would end up using carbohydrates (CH) and fats when the rhythm was stabilized.

The best results in endurance activities occur when the body has unrestricted access to the glycolytic pathway (carbohydrate pathway). However, this pathway is limited by the storage capacity of the deposits of this energetic substrate. The key, therefore, is to be able to preserve glycogen stores for as long as possible using the lipid pathway (that of fats) and gradually replenish glycogen stores while doing the activity.

Current technology allows us to evaluate the energy expenditure of the activities we carry out and with statistical models to make a fairly accurate approximation of the energy sources that make it possible. This tool makes it possible to calculate nutritional intake in competitions and demanding training sessions, as well as to evaluate the suitability of the way our body works for a certain activity. In this way, and analyzing each sports discipline and its energy demands, we will seek that with the training plan and the diet, we get closer to what would be optimal for each competitive activity in which we are involved.

The thermoregulatory system

Carrying out any physical activity causes a significant increase in body temperature. The environment helps or harms depending on whether it is cold or hot and/or dry or humid.

For this reason, and depending on the intensity of the exercise and the environmental conditions, the body acts with its body temperature regulation mechanisms to keep it within the narrow tolerable range.

When the environment where physical activity is carried out is hot and humid, the body needs to release heat by evaporating the sweat it generates through the skin. These losses cause an immediate imbalance in the water balance if they are not compensated, leading the athlete to a state of dehydration when they represent 2% of body weight. The immediate, relatively less serious consequences are a drop in performance. If the imbalance persists and worsens, it leads to disorientation problems, arrhythmias and even loss of consciousness, among other less visible but equally serious consequences.

Given the importance of the thermoregulatory system in carrying out any resistance activity, it will be very positive for performance to adopt a series of measures that favor its action or at least harm it as little as possible.

These measures must initially be of a palliative nature, correcting the loss of sweating through the intake of appropriate drinks for this purpose in order to try to recover the water balance. This can be complicated the more extreme the climate is, since the stomach has a gastric emptying limit of approximately 1.2-1.5 l/h. For this reason, if the losses are greater than our absorption capacity, we will suffer dehydration that, if prolonged over time, will end up being severe, with the consequences that this entails.

Any action aimed at lowering body temperature is a good option to recover the physical level lost due to hyperthermia. Cold drinks, getting into the icy waters of a torrent, putting snow under your clothes to cool your body or cooling vests are good options when the heat and humidity grip us.

Apart from keeping cool with palliative measures, the other way to avoid hyperthermia is as many drivers used to do when they went up a pass with an old vehicle. They controlled the temperature of the water in the radiator at all times and according to this they regulated the speed, even stopping in the ditch before blowing up the cap of the cooling system.

Bodily we must also do it. The heat that overwhelms us comes both from the external environment and from the heat that we generate with our metabolism as a result of our effort. For this reason, we must choose a rhythm that is appropriate to the possibilities offered by the environment.

For all that has been said, el self-knowledge is a fundamental weapon to keep the temperature at bay, looking for a compromise between the level of intensity of effort and the possibilities of rehydration to compensate for hyperthermia of extrinsic (the environment) and intrinsic (the effort) origin. . In this way we will ensure that the thermoregulatory system works correctly and continues to integrate correctly within the set of systems that determine performance in resistance activities.