Food And Physical Activity, A Book That Tells You The Relation Between Food And Physical Activity

The effectiveness of the muscle to generate force and movement depends on the ability of the muscle cells to contract and, as in other “machines”, on the fuel it uses. Therefore, it is not strange the interest aroused by the relation between the feeding and the muscular efficiency.

The fuel

Until the beginning of the 20th century it was thought that the ideal fuel for muscle was proteins, which needed to be supplied in the form of meat. These ideas motivated for example problems of supply of the German army in the first world war, that according to the beliefs of the moment it had to eat per capita almost a kilo of meat daily.

Nowadays we know that this is completely false and that muscle uses as fuel glucose, fat (like fatty acids) and creatine phosphate, but not proteins. And we also know that it is possible to improve the physical performance with an adequate diet, which varies according to the type of exercise.

The fuel used preferably by the muscle depends on the intensity of the exercise performed, the duration of the muscle and the ability of the muscle cells to store glucose in the form of glycogen and creatine phosphate.

Creatine phosphate is a molecule that is found in the muscle and stores energy. It can release a lot of energy, but only for a few seconds.

When the accumulated glucose in the muscles is depleted it begins to consume glucose from the blood, but at a slower rate.

Muscle then depends primarily on fat to generate energy. The latter can produce energy for a long time, but at a low intensity that does not allow great efforts, although it allows prolonging physical activity for a longer time.

Glucose is the main energy source and can be used in two different ways:

  • Anaerobically (without oxygen consumption). By this method it releases energy quickly (not as quickly as creatine phosphate), although inefficient, since it only supplies 10% of all its energy potential; And also for a short time, depending on the glycogen accumulated in the muscle.
  • Aerobically, that is to say, it burns with the oxygen supplied with the breath, it releases all the energy accumulated in its molecule, but of slower form that in anaerobic conditions, which allows to exercise for hours, but not of so much intensity.

In general

Athletes do not need vitamin or protein supplements. Exercise increases your energy needs and by eating more you take more protein, minerals and vitamins, so you do not need to ingest additional amounts.

Energy consumption in light and rest exercises

At rest or with a normal activity of daily living, such as holding the newspaper while we read or when we walk slowly, the muscle mainly uses fatty acids. For these activities does not require much energy, which can be supplied with the combustion of fat; Muscle prefers to reserve the most powerful fuels (glycogen glucose and creatine phosphate) for more important situations.

Energy consumption during intense and short exercises

To perform exercises that require a lot of strength in a short time, such as weight lifting, hammer throwing, etc. The muscle uses stored energy as creatine phosphate, since no other method can release as much energy in the instant that such an intense effort lasts.

In intense and short but somewhat longer exercises – such as 200 meters smooth – creatine phosphate can not sustain this exercise, and to maintain it is used to use glucose anaerobically, even if it involves a waste of energy.

Energy consumption during intense and prolonged exercises

To perform this type of exercise, such as running the 1000 meters, it is necessary to use all the energy stored in the glucose, which is why it is used to aerobic combustion of it, ie burning it with oxygen. In this way glucose releases more energy, but more slowly. It is not possible to maintain the same speed as in the 100 meters smooth, but it is possible to maintain the effort for a longer time, mainly depending on the glycogen in the muscle.

If the exercise is not very intense and the person is trained can maintain the effort for 1 to 3 hours. As the effort is prolonged fatty acids are consumed in greater proportion. When muscle glycogen is depleted, as in the second half of a marathon race, the speed of the runner is limited by the energy supplied by the ability to oxidize fatty acids, which release energy more slowly and so the runner looks Unable to increase the speed of the race, although it puts all its effort.
Power and physical performance

It is possible to improve the ability to perform explosive exercises by increasing the amount of muscle creatine phosphate. To do this you can take supplements of this substance for periods of a week to a month of duration before the exercise.

The most important effect of feeding to increase physical performance, especially in sports trials of more than 60 minutes duration, occurs thanks to the ability to increase muscle glycogen reserves. In fact, the increase in physical performance that occurs within a few weeks of starting the workout is primarily due to improved storage of glycogen by the muscle and its ability to increase the combustion of glucose and fatty acids.

The amount of muscle glycogen can be increased with an adequate regimen of food, exercise and rest. In the first place, it is advisable to do some exercises before the competition that consume all the muscular glycogen. In this way, the uptake of glucose by the muscle and its storage as glycogen is stimulated. The periods of muscle glycogen depletion should be followed by two to three days in which moderate exercise and a diet rich in carbohydrates of slow absorption are performed. The sequence of the exercise regime, feeding and rest vary depending on the moment in which the athlete is and according to their training or competition situation.


During prolonged exercises and especially in hot environments it is necessary to pay attention to hydration, since the loss of liquids and mineral salts in the sweat greatly diminishes the performance. Moisturizing solutions should contain glucose, which contributes to saving muscle glycogen, a small amount of sodium chloride. These solutions should be taken at about 10 or 12ºC of temperature, shortly before beginning the exercise and during the duration of this of east, to replace the losses of liquids.

Athletes do not need vitamin or protein supplements. Exercise increases energy needs and by eating more, you take more protein, minerals and vitamins than necessary, so you do not need to ingest additional amounts. Only a few young girls may develop anemia due to lack of iron, which in this case requires palliation with supplements.