A proper balanced diet should provide all the necessary components and cover our energy requirements, which include needing energy for;
The are major differences between sports in terms of how many calories the activity burns.
For example, if you are climbing the Mont Blanc in two days, you will need to consume 9000Kcal each day, a leg of the Tour de France requires you to consume 6000Kcal a day and you need to consume 5000Kcal to compete in a triathlon. When the amount of calories to be consumed are this high, it is fairly difficult for the athlete to balance the calories burnt with food consumption. However, this balancing rule must be respected even if this is done so over a long period of time. If not enough calories are consumed, the individual will lose weight, mainly at the expense of their body fat, but also their muscle mass.
The main ‘fuel’ used in resistance sports is fats. Fats are usually available in the body and, contrarily, there are not usually a lot of sugars available. Sugars found in the body are present in the muscles and liver in the form of a polymer called glycogen (approximately 200g in muscles and more in the liver) and as glucose in the blood (with a concentration of 0.1g/dl). Even during a test of resistance (for example, a marathon or a hike) sugars are always available, even though using fats are preferred in this case. Furthermore, despite the fact that the muscles have a certain amount of ‘fuel’ stored, they must also rely on energy coming from the blood.
For example, for an exercise that lasts 3 hours, around 86% of the oxygen consumed goes to oxidising fats and glucose, which comes from the blood (50% and 36% respectively), and only 14% is needed to oxidise the substrate found in the muscle. What normally happens, however, is that there is a lack of sugars due to hypoglycaemia, thus it is important to replenish these sugar ‘stocks’. The typical symptoms of hypoglycaemia are extreme fatigue, nausea, blurry vision and headaches. This condition can be prevented by slowly introducing sugars to compensate for the loss. Dehydration is often a problem too, as well as sugar depletion, and to prevent this from happening you need to drink 100-120ml of a drink that contains glucose (a concentration of 3-5%) and salts (enough to compensate for the salts lost when sweating) every 20 minutes. When the body gets close to a hypoglycaemic state, it activates a special metabolic path in the liver which, starting from the ramified amino acid alanine, enables the synthesis of glucose.
Let us now look at those who dedicate themselves to strength sports. The main
problem linked to these sports is the fact that this type of training induces
muscular hypertrophy and therefore the body must be provided with a large amount of protein which will
enable new protein matrixes to be created. Proteins come from meat, cheese, milk, cereals (durum wheat) and some pulses (beans,
peas, lentils, chickpeas). The average requirement, in terms of protein, is 1g/kg
the athlete weighs per day.
Weight lifters, bodybuilders and gymnasts tend to eat 3g/kg they weigh each day but physiology research in this area does not confirm the need to consume this much. Surprisingly, athletes who do resistance sports need more protein that the aforementioned athletes since, when training, they must run at least 20-30km per day.