Carbohydrates are an energetic substrate NECESSARY for the survival of the human being; their quantity / percentage in the diet (whether it is weighted, in excess or in defect) greatly affects the general state of health of the individual; moreover, there are conditions / situations in which carbohydrates play an even more important role: one of these is aerobic physical activity.
Carbohydrates: functions and dietary role in aerobic physical activity
Animals and humans, unable to COMPLETELY comply with their glucose needs through neoglucogenesis (production of glucose starting from amino acids, lactic acid and glycerol), must obtain it by eating foods that contain sufficient quantities of carbohydrates, therefore: cereals (cooked ), legumes (cooked), tubers (cooked), fruits, leaves and roots.
Glucose, derived from dietary carbohydrates and from neoglucogenesis, is essential for cellular respiration of tissues, let's see why. In the production of energy with the use of oxygen (aerobic metabolism), carbohydrates (glucose), such as fatty acids and some amino acids, are processed into Acetyl-Coenzyme A and placed in Krebs cycle with the aim of reloading the transporters NAD And FAD, then engaged in the oxidative phosphorylation necessary for the activation of the pump ATP-synthase. On the other hand, the Krebs cycle constitutes a real "perpetual ring", whose starting and ending molecule is represented by" OXALACETATE; this, tying l "Acetyl-Coenzyme A, determines the start-up of the cycle itself and is ESSENTIAL for the correct functioning of the entire system. Although (strictly speaking) the Krebs cycle must be concluded with a "unit of oxaloacetate, often these molecules undergo a deterioration; it is therefore obvious that, when inactivated, the" oxaloacetate needs to be replaced. But how?
The precursors from which it is possible to obtain oxaloacetate are:
- Pyruvate - derived from glucose
- Asparagine or aspartic acid - non-essential amino acids
In basal conditions, the cycle can be perpetuated easily by drawing indiscriminately from one or the other precursor; on the other hand, the same does not happen during prolonged aerobic physical-motor activity. In this situation, given the rapidity with which cellular respiration occurs, the presence or absence of oxaloacetate can become a LIMITING FACTOR; to ensure that the mechanism "DOES NOT get stuck" it is essential to guarantee the presence of its precursor PIU "EASY and MORE" QUICK to use, that is the pyruvate obtained from glucose (carbohydrates). It is undeniable that also "asparagine or" aspartic acid can contribute to the purpose, but considering the slowness with which they are used and their scarce presence in the diet (therefore in the organism), it can be defined with certainty that glucose (obtained by means of dietary carbohydrates and / or by neoglucogenesis) constitutes an energy molecule NECESSARY for prolonged and aerobic physical-motor activity.
Carbohydrates for aerobic activity: how many, which and from what food sources
Once it is clarified WHY "carbohydrates are necessary for sustaining prolonged aerobic physical-motor activity, it is necessary to UNDERSTAND better: how many to eat, what type and in what foods to find them.
HOW MANY carbohydrates for aerobic activity? Let's say that the quantitative estimation of carbohydrates in the diet is always empirical, therefore the relative nutritional application can prove even more difficult than expected. Leaving aside the overall macro-nutritional breakdown of the day, in this article I think it is more appropriate to focus on the real need to introduce carbohydrates for the purpose of performance, even if the estimate of one cannot totally disregard that of the other; in fact, the availability of glucose during the performance depends above all on:
- Intrinsic muscle stores (full muscle glycogen stores)
- Glycemic homeostasis (fullness of the liver glycogen stores)
Both of these factors are influenced by the diet and post-prandial insulin flows of the several days before: therefore, the meal preceding the workout or the prolonged endurance race (however abundant) is never sufficient to completely guarantee the carbohydrate requirement for prolonged aerobic muscle contraction. On the other hand, while assuming that the sportsman / athlete's diet is sufficiently distributed and balanced, it is possible to state that the carbohydrates useful for the practice of prolonged aerobic activity must be introduced in any case before, during (in particular when it comes to efforts that well exceed 60 ") and after the performance. Obviously, in order to avoid an energy overabundance with consequent adipose deposit, it is ALWAYS necessary to estimate the caloric consumption and differentiate the energy intake in the 3 moments described above. We remind you that, during the effort, according to the intensity and the level of training, the mixture of the various energy substrates (glucose, fatty acids, amino acids) changes considerably and follows approximately these two equations:
- PERCENTAGE consumption of fatty acids and <PERCENTAGE consumption of glucose and amino acids (branched and non-branched)
- > intensity => PERCENTAGE consumption of glucose and amino acids (branched and non-branched) and <PERCENTAGE consumption of fatty acids.
As for the intake of carbohydrates before physical activity, I strongly suggest avoiding large portions and respecting the digestion-absorption times; the sooner the meal is consumed, the greater the relative caloric importance may be; on the other hand, close to training / competition, it would be advisable NOT to exceed 150kcal (spannometric evaluation of the collective digestion potential). During the activity, however, the intake of carbohydrates is mainly constrained by the osmotic potential of the rehydrating drink, as a source of sugars, water and mineral salts (sometimes also branched amino acids); personally, I do not recommend using solid foods during the effort (unless real and concrete needs arise), therefore, the amount of carbohydrates to be taken during training / competition corresponds to that mixable in a slightly hypotonic drink with a volume of approximately 1.5 liters. In the meal after the effort it would be good practice to introduce carbohydrates as soon as possible and, in any case, I suggest to keep in mind that, often, from there to a little could to arrive at the time of a main meal; in this situation the partial DISSOCIATION of nutrients with glucose prevalence in the immediate post-workout and protein-lipid prevalence in the ordinary meal proves extremely convenient. Taking a short example, assuming a consumption of about 600kcal with medium-high intensity, 60-80% of the total MUST be met by the diet; in practice, about 400kcal will be divided into 150-170kcal before, 60-100kcal during and 150 -170kcal after.
WHICH carbohydrates for aerobic activity? To establish which carbohydrates are necessary for the activity it is necessary to think both about the function they play and the context in which they are inserted. Assuming an OPTIMAL condition, it is possible to state that:
- Carbohydrates to take first of aerobic activity should be of medium-low glycemic index, in order to distribute their perfusion in the body for the entire period of time preceding the performance, thus avoiding the occurrence of the glycemic-insulin peak; moreover, it is better to prefer molecules complex avoiding to exceed with fructose (contained above all in fruits and whose contribution is to be correlated to that of dietary fiber)
- Carbohydrates to take during aerobic activity should be medium-high glycemic index, to allow rapid absorption and an equally fast use
- Carbohydrates to take after aerobic activity should be:
- High glycemic index if introduced in the "immediate post-workout (first 15" or at most within the first hour)
- Medium-low glycemic index if introduced after more than 60 "from the end of the session.
FROM WHICH FOOD SOURCES would I take carbohydrates for aerobic activity? In compliance with what has been stated so far, it is possible to state that the most suitable carbohydrate sources at various times are respectively:
- Long before (about 2h) of aerobic physical activity: low-refined foods and foods or foods containing low-refined carbohydrates or made up of ingredients with a fair amount of dietary fiber; mainly fruit (no more than 300g at a time and possibly in combination with other foods) , vegetables, rye bread, wholemeal bread, basmati rice with oil, pasta with vegetables, rice with vegetables etc.
- During aerobic physical activity: MIXTURES of maltodextrin, vitargo, sucrose, glucose and fructose
- After "aerobic physical activity: MORE" refined foods and foods or foods containing refined carbohydrates and FREE of ingredients with a fair amount of dietary fiber; mainly plain white pasta, plain white rice, white bread, plain polenta, biscuits, bananas, unseasoned boiled potatoes, etc.
By following all these indications it is possible NOT only to improve recovery, therefore performance, but also to compose a possible mildly hypocaloric diet aimed at weight loss, in conjunction with aerobic physical-motor activity, WITHOUT running the risk of running into muscle catabolism induced by "insufficiency of carbohydrates in the diet.
