In the article “The energy cost of high-impact aerobics, based on experimental data, was calculated how much energy is spent during an aerobics class and, above all, the ways in which this” energy expenditure “takes place. note that usually aerobic students tend to practice at an intensity that is, albeit not too much, higher than the limits of purely aerobic work.These data should be extremely useful for Instructors when they are preparing to define the choreography of a lesson This is even more true if we also take into account that research has shown that, since not all subjects possess the same physical abilities, for some the lesson is particularly demanding, for others widely within the limits of an aerobic commitment.
In this article the experimental data of the quoted article are still analyzed to try to draw other interesting information, in particular concerning a fundamental aspect of human life: nutrition.
When considering the energy cost in terms of weight loss, there is an unrewarding situation (at least for those with the goal of losing weight), as the real weight loss goes from about 50 grams for beginners to about 85 grams for experienced men. These values have nothing to do with the kilo that is missing on the scale at the end of the lesson which is determined almost exclusively by the loss of water. This is the unequivocal demonstration of the uselessness of exasperating perspiration with waterproof suits during the activity, since the weight loss that is determined is purely illusory and is immediately compensated by “drinking”. When you want to translate into food the real scope of an aerobics class, such as the one we monitored, we see that, at the end of the lesson, it is enough to order a cappuccino with a brioche at the bar for the expert men to reintegrate the expenses and beginner women have even gained a few grams. From what has been said it is clear that those who decide to use aerobics as a means to lose weight can not disregard the integration of physical activity with an appropriate diet, while those who have the goal of keeping fit should not consider the time of lesson as a pleasant, even if tiring, viaticum for a Lucullian dinner.
An equally important aspect related to energy expenditure as a function of food replenishment is given by the analysis of energy substrates that are used by the body to produce the energy needed for movement (this analysis is possible from the analysis of the consumed oxygen and carbon dioxide produced). If we analyze in fact the sources from which the energy used during the lesson comes, we see that most of this comes from the burning of sugars. In fact, sugars contribute for 66% in men and 72% in women to supply energy. This means on the one hand that the exercise is too intense to be classified as purely aerobic and on the other hand that the slimming effectiveness of the same is greatly reduced by the fact that the intensity is high.
In fact, as known, the body “chooses” as “petrol” for its muscles alternatively sugars or fats in relation to the intensity of the effort. When this is challenging, the muscles resort to sugars, while when it is mild or moderate, the fats are burned. This is the reason why the recommended motor activity to reduce fat reserves (weight loss) is essentially that of long duration at low intensity (jogging, jogging, swimming, cycling, etc). Among these undoubtedly also includes aerobics, but when it is really “aerobic”, that is, of long duration and low intensity, while this does not seem to be the case of many lessons, including those monitored.
In conclusion, it is our opinion that an aerobics class, such as those we studied, has a significant effectiveness on the cardiovascular system and therefore is of appropriate entity, when it has the purpose of maintaining physical efficiency and is practiced by individuals who have already a good state of training. On the other hand, we believe that it is of excessive intensity for all those who start practicing physical activity or whose goal is slimming.
This last aspect is particularly important because it has been calculated that a loss of water equal to 2% of body weight determines a significant reduction in the performance capacity of an individual. In other words, if a 70 kg man loses 1.4 liters of water with sweat and does not reintegrate it quickly, his physical abilities are greatly reduced and what at first might seem like a pleasant lesson becomes an increasingly heavy physical effort. If water losses continue, without recourse to continuous and adequate reintegration, and you get to exceed the 4% quota (in many races such as cycling or marathon this is the norm) then you risk the same life for the onset of the “heat stroke”. This is certainly not the case for aerobic practitioners, who record water losses ranging from 0.6 to 1.2 liters, which, in terms of percentage of body weight, reach the highest value in experienced men and women (1.6%). These values are not dangerous, even if they place themselves at the limits of compatibility with the maintenance of physical efficiency (beginner women, on the contrary, are largely within these limits, thanks to the modest energy expenditure they highlight). However, if we consider that most of the energy expenditure takes place in the aerobic phase proper (50% of the total), we understand how slight prolongations of this phase would have very marked effects on water loss.
In any case, whatever the hypothetical further aggravation of water loss, even the one recorded by us is such as to require an adequate and immediate reintegration, even during the lesson itself, so that the body is able to meet the needs of thermoregulation. , without the occurrence of situations of excessive physical stress that would make the practice of sporting activity less gratifying, as well as less useful.
The need for rapid and adequate reintegration is not just about water. In fact, if we analyze the content of the sweat, we can see that this is not only composed of water but also contains a certain number of minerals: in particular sodium (Na +), chlorine (Cl-), potassium (K +) and magnesium ( mg ++). If water has the task of maintaining constant body temperature, mineral salts play equally important functions in the body. In particular, those present in the sweat participate in the regulation of the electrical balance of the nerve and muscle cell membranes (Na + and Cl-) or the enzymatic regulation of numerous metabolic pathways for energy production (K + and Mg ++). The lack, or rather, the reduction of the content of these minerals in the organism, therefore, can become the cause of a not perfect functioning of the muscular contraction processes and therefore of a reduction of the same performance capacity during a physical activity.
It follows that the non-reintegration of both water and salts can cause excessive stress to the body. It is therefore evident that already during the lessons it is necessary to provide an immediate reintegration not only of the lost liquids, but also of the salts. The reintegration must then be completed in the days of inactivity, to avoid that the addition of the losses that occur in the various weekly sessions can lead to a condition of chronic hydro-saline deficit.