Controlling intensity in training

Almost systematically, I find myself in consultation with athletes who are training at inadequate intensities, only a few are spared. And, as in almost everything, the dose is important.
In general, this is due to the tendency, due to time commitments, to get things done in the shortest time possible. And that, in this case, generally means training the distance you play, but in less time, or vice versa. There is a general feeling, and thus it is transmitted regularly by different media, that training, if it does not generate a fatigue situation, if we do not have the feeling of having trained a lot, it does not generate improvement. And that is wrong, what the training should generate, at least when doing background training is, adaptation.
Let us imagine that our body is like a car that works with two engines, at low one diesel (fat), at high one gasoline (carbohydrates). The gasoline gives reprise -changes of rhythm- and allows high speeds, but consumes a lot, and the gas tank is quite limited. And if that deposit is emptied, either suddenly, or due to a process of high consumption continued over time, it causes a drastic drop in performance (pajara/overtraining). However, the diesel works at low rates, and does not allow bragging about sudden changes in intensity or sustained high intensities, but it has an almost unlimited fuel tank from the metabolic point of view (fats). If we go at a "diesel" rate and ask to have more energy available (we increase speed), there comes a point where a compromise occurs, due to the high costs of extracting energy from this substrate (beta oxidation), with which the system changes to a "gasoline" engine (glycolysis).
Therefore, what we have to do is "teach" our body to use fat more efficiently. It would be like doing the filming of an engine, bring it to its highest possible speed before it loses efficiency, and so little by little you adapt, so that the cruising speed will increase, without wasting carbohydrates.
That starting point of the loss of efficiency of fats as a fuel source is called AEROBIC THRESHOLD (not anaerobic) and It's the key for the correct control of training intensities. The problem is that for its determination there is no other method other than performing a stress test with control of breathed gases (ergospirometry), or lactic acid in the blood. No other.
On the other hand, it could occur to us that, in order to force fat to be consumed as an energy source, we can manipulate the system and force it to do so. So we went out to train in fasting, and more to more, with a previous dinner low in carbohydrates (the latter has already deserved to be a separate topic). Error. Because, if you go at a minimally high intensity, the initial condition for using fats as an energy source is still met, the extraction costs! So, since we are going to the rhythm of carbohydrates, but we do not have them, the body will use its metabolic cousin, proteins (Neo-glycogenesis is called the process). With which the paradox is generated that we are training without improving physical condition, without reducing fat deposits, and on top of burning our own muscle !!!
 
Luis Garcia del Moral
Physical Education and Sports Medicine
Extracted from his blog: http://www.luisgarciadelmoral.com/2017/07/el-control-de-la-intensidad-en-el.html