The sportsman's plate: nutrition tips

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Extract from the article: In addition to covering their basic nutritional needs, athletes must pay particular attention to their carbohydrate intake before, during and after a sporting event, while optimizing their protein intake.

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In addition to covering their basic nutritional needs, athletes must pay particular attention to their carbohydrate intake before, during and after a sporting event, while optimizing their protein intake.

When we talk about sports nutrition, we're talking about covering energy and nutritional requirements, including macronutrients (carbohydrates, proteins) and micronutrients. These are higher than those of the general population, due to the high energy expenditure of athletes.

Contributions to specific carbohydrates

Carbohydrate intake is the first specificity of sports nutrition. Dependence on glucose as an energy source (stored as glycogen) increases with exercise intensity. The use of fatty acids (fat) as energy fuel is rendered impossible by this phenomenon. However, a trained person will be able to use more fatty acids for a specific intensity.

What's more, the amount of glucose available in the body is limited: around 120 g of glycogen in the liver and 254 to 400 g in the muscles of highly trained athletes. Given the limited amount of energy available for intense exercise, it's vital to start training sessions or competitions with maximum glycogen reserves. Today, it is recommended to consume between 10 and 12 g of carbohydrates per kg of body weight in the two days leading up to the event.

Maintaining reserves until the start of the race

Between the last meal, which should be taken around 3 hours before the start of an event, and the start, it is necessary to maintain glycogen reserves. This “waiting ration” is made up of small quantities of low-glycemic index carbohydrates.

Carbohydrate intake throughout the eventCarbohydrates must be available throughout the event, to maintain energy levels and avoid depletion of glycogen reserves. Carbohydrates must be supplied continuously, particularly when the day's duration exceeds 60 to 90 minutes. Below this level, reserves are adequate to cope with the effort involved. We recommend consuming around 30g of carbohydrates per hour for exercise lasting between 1 and 2 hours.When exercise is prolonged, carbohydrate intake needs to be adjusted accordingly.Very long exercise sessions are a special case. The intestine's capacity to absorb more than 1 to 1.2 g of glucose per minute is effectively limited.A trick has been discovered: athletes then consume another carbohydrate: fructose. When glucose and fructose are combined, the total amount of absorbable carbohydrates available to the body is increased. It is therefore advisable to ingest 90 to 100 g of carbohydrates per hour for exercise exceeding 2h30. These carbohydrates are made up of glucose and fructose. There are even “digestive tract training techniques” for increasing carbohydrate intake up to 100-120 g per hour in certain extreme endurance sports.

Proteins for post-exercise muscle rebuilding

Another particularity of sports nutrition concerns protein intake. Muscle is constantly being built and destroyed, much like bone. During exercise, muscle protein destruction increases, while protein synthesis decreases, which can lead to muscle loss. Conversely, as soon as exercise ends, protein synthesis increases considerably for around 3 hours. During this “anabolic window”, the body needs to be supplied with amino acids (protein building blocks) to rebuild the proteins degraded during exercise. So, to “limit the damage”, we recommend ingesting proteins ideally within 30 minutes of exercise. These proteins should be rich in essential amino acids, in particular leucine, dairy proteins, in particular whey proteins, rich in leucine, and fast-acting proteins (whose amino acids are rapidly available). The optimal amount of protein is 0.35 g/kg body weight.

More carbohydrates in the recovery phase!

It's important that the recovery ration also includes carbohydrates.Since muscle glycogen must be replenished, it is also necessary to provide the energy needed for protein synthesis, in particular by using high-glycemic index carbohydrates. We recommend one proportion of carbohydrate to one proportion of protein for strength/power sports, and three proportions of carbohydrate to one proportion of protein for endurance sports.Jean ELI

Source: Pr Xavier Bigard, Sports Physician, Exercise Physiologist, Nutritionist and Scientific Advisor to the French Anti-Doping Agency, Paris (France)