All of the cells and tissues in an athlete's body contain proteins. They can be found in the muscles, the bones, the hair, the nails, the skin… They make up for around 20% of the total body mass. Proteins are used to construct and rebuild the body. Their key role is to allow the growth and replacement of tissues ;Their use for energy is however limited.
The role of proteins in the athlete's body
The body's proteins are structural and functional elements present in all of our tissues. They are used as enzymes, but are also constituent components of supporting tissues, part of the cell architecture, or contractile components in the muscles... It is impossible to provide a comprehensive list of their actions in our tissues. The lifespan of proteins varies, requiring the daily replacement of those that have been damaged and eliminated.
- At a tissular level, proteins help with the mechanical support of tissues. Examples of these include collagen, elastin and keratin. Collagen is the most abundant protein in the body.
- Proteins also provide mechanical support within cells. The cell shape is in fact directly linked to proteins (actin, myosin, ...)
The role of proteins is vital to different functions:
- For blood transport. Several chemical substances are transported around the body by being temporarily combined with a protein. For example, albumin allows fatty acids and certain vitamins to be transported, haemoglobin allows oxygen to be transported in the blood and myoglobin allows oxygen to be transported in the muscles.
- For coagulation
- For membrane transport. Proteins control the exchanges between the cells and the extracellular medium.
- As hormones, such as insulin, glucagon, etc.
- Enzymes are proteins that regulate the body's biochemical reactions.
- As antibodies: They are made in the white blood cells to defend the body from foreign cells.
- For movement thanks to the contractile proteins in the muscles. Muscle contraction is due to the interaction between two proteins: actin and myosin.
From a metabolic point of view, the amino acids can also serve as energy sources. However, proteins cannot be regarded as a comparable energy reserve to carbohydrates and lipids. The use of proteins for energy in the body is relatively limited. On an empty belly, proteins can provide up to 10% of the total energy requirements. When working out, the portion of energy provision coming from proteins is only 5%.
For which sports are proteins recommended?
Muscular proteins are very important for athletes, due to the key role they play in the muscle structure.
It's important to make a distinction between endurance and strength sports.
Long-duration workouts may alter the integrity of proteins structures (muscles, tendons). Among runners, for example, the shockwave generated each time the foot hits the ground has a destructive effect due to its repetition. This phenomena tends to stimulate muscular protein biosynthesis and allows the regeneration of damaged tissues. Therefore the need for protein is higher among athletes taking part in intensive, long and repetitive exercise. In France, the recommended dietary allowance for someone regularly practising endurance sports is 1.5 to 1.7g / kg / day.
The aim for these athletes is to develop muscle mass and therefore to increase the amount of stored protein. In France, the recommended dietary allowance (RDA) for athletes regularly practising strength sports is a protein intake of 1 to 1.2g / kg / day if the person does not want to increase their muscle mass, and an intake of 2 to 3g / kg / day to achieve muscle hypertrophy. However, the RDAs also specify that this intake should not exceed 6 months per year, and that a medical follow-up is recommended.