Nutrition for athletes is a matter of nutrients
The more glycogen, the further and faster the player runs (Kirkendall, 1993).
Glycogen is the complex carbohydrate responsible for storing energy in muscles, a topic that is mentioned in all books about nutrition for athletes. Human beings get the energy they need to perform physical exercise from the diet, more specifically from dietary macronutrients: fat, carbohydrate, protein and alcohol.
In this post, I am going to briefly introduce each macronutrient and explain the relevance for athletes.
Nutrition for athletes: carbohydrates
Grains, legumes (pulses), fruit and, to a limited extent, vegetables, all contain carbohydrates. The latter provide fast energy during physical exercise and represent the most common energy source for muscles. Carbohydrates are stored as glycogen in the liver and skeletal muscle. Although liver glycogen is more relevant for the maintenance of stable blood glucose levels, the glycogen accumulated in muscles is used as a source of energy during exercise and is quickly depleted. This is the main reason why carbohydrate intake should be maintained before, during and after training. Excess carbohydrate in sedentary people is easily converted to fat.
Nutrition for athletes: fats
Fats are also a source of energy and can be used by muscles during exercise. Fats are stored as triglycerides in the adipose tissue, but also as intramuscular fat (as triacylglycerol droplets) and, although in small amounts, even in plasma. Although carbohydrates are usually regarded as the preferred source of energy during exercise, endurance athletes can adapt their metabolism to store more fat droplets in their muscles and spare glycogen during exercise.
Nutrition for athletes: proteins
Often regarded as a major source of energy during physical exercise, proteins have instead a structural function and play a big role in the recovery and repair of damaged muscles fibres. Proteins are made of amino acids, which can be synthesized by the human metabolism, exception made for some, which are known as “essential”: phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine. These must be obtained from the diet. Protein can be converted into glucose and free fatty acids, when there is not enough energy available and an alternative source is needed.
Nutrition for athletes: alcohol
Alcohol is not recommended before, during or after exercise. Since its metabolism requires a lot of water, consuming alcohol can cause dehydration, which reduces physical performance. Alcohol also increases heat losses, causes vasodilatation and impairs the recovery and repair phase after exercise. Finally, alcoholic beverages can increase urinary water losses, another reason why athletes are strongly encouraged to consume alcohol only away from training and competitions.
Nutrition for athletes: summary
- Both carbohydrates and fats represent potential sources of energy during exercise;
- Proteins are more important for the building of muscle fibres and their recovery and repair after training;
- Alcohol consumption is strongly discouraged in all athletes and can severely reduce physical performance.
Did you know that?
When carbohydrates are used as fuel, some water is lost with them. Also, physical training causes loss of water as sweat. These are all reasons why the requirements for water increase during physical exercise.
Daries, H. (2012) Nutrition for Sport and Exercise : a Practical Guide. Wiley-Blackwell.
Kirkendall, D. T. (1993) ‘Effects of nutrition on performance in soccer’, Medicine and science in sports and exercise, 25(12), pp. 1370–4.