Endurance sports and nutrition

The right nutrition for enhanced athletic performance

Sports nutrition (the energy needed for a physical activity) is a very specific topic in nutritional science. It has to provide the energy for muscle function as well as nutrients necessary for the next training. What the total energy requirements are, depends not only on the type of sport but also on its duration, intensity, athlete’s body weight and climatic conditions (such as altitude).

Endurance sports rank among moderate-intensity physical activities (some sources use quite an accurate term “submaximal intensity load”) and long-duration activities (moderate endurance load 2-11 minutes, high endurance load 10s of minutes up to several hours).

Aerobic metabolism and energy intake

When talking about endurance exercise, were talking about aerobic exercise. I’ll tell you something about the physiology behind physical load, so that you can better understand how to eat right. During aerobic exercise, the body “burns” sugars (glycometabolism) and fats (lipid metabolism). In practice it works like this: at first it uses the energy from the reserves of glycogen stored in muscles (glycogen is a polysaccharide composed of several glucose units). There is about 250-300g of it in our muscles, about 400-700g in athletes’ muscles. Then it uses the energy from liver glycogen, which is about 100g. This process is called oxidative phosphorylation during which from 1 molecule of glucose we get 38 molecules of ATP. When the level of glycogen falls (about after 20-30 minutes) or during a lower-intensity physical activity, the body simultaneously moves on to lipid metabolism. In this case the muscles use energy from fats by the process of fatty acid beta-oxidation, and the fatty acids are released from triglycerides. This process is called lipolysis; and 17 ATP molecules are synthetized. After 90 minutes of physical activity, gluconeogenesis takes place, ATP is produced from amino acids. In lay’s terms we could call it “eating up one’s own muscles” and this phenomenon is, of course, not desirable because by physical training we want to gain muscles and not lose them. Apart from that we gain only 12 ATP molecules from 1 molecule of glucose (produced from amino acids) which is not so energetically beneficial either.

How does oxygen affect us?

And to make things a bit more complicated, I’ll tell you something about a limiting factor for performance – the maximal oxygen uptake VO2max. (VO2max –the maximal amount of oxygen that a body is able to uptake in 1 minute during an intensive physical activity in). In other words: the more oxygen you’re able to uptake (breathe in), the more sugars and fats will be broken down, the more ATP is created, the more energy will be available for the cell, and the better your performance will be. It’s called aerobic exercise – because oxygen is used during the process.

Time to eat or how what you eat affects your performance

Before the physical activity:

Recreational athletes should eat their last meal 1–2 hours before training (depends on the person). For professional athletes, the last solid meal should be eaten 3–5 hours before the physical activity. About 1–2 hours before training it’s recommended to eat some snack, ideally one with a low glycemic index (GI) to prevent hypoglycemia. That could occur if insulin is released into the bloodstream after we consume high GI food. Before the performance you should also avoid fatty and spicy foods and eat proteins in smaller and more frequent portions, so that they’re better utilized. Recreational athletes should consume 1,2 g/kg/day of protein, strength athletes 1,7–2g/kg/day. It’s also recommended to drink enough water and to compensate for sodium (Na) losses. The level of hydration can be easily stated by checking the colour of urine (the darker the urine is, the more dehydrated is your body).

During the physical activity:

During a higher-intensity physical activity its necessary to replace fluids and ions, ideally by drinking ion-supply drinks (sports drinks). It’s also advised to replace carbohydrates every 15 minutes or so. It’s better to eat both glucose and fructose together because glucose alone has a high GI and after consuming (only) fructose you might feel sick.

After the physical activity:

After the performance its necessary to continue to re-hydrate and replace the lost ions. Another important step is providing the body with saccharides. That should be done until about 2 hours after the training and you should prefer higher GI foods (so as to replenish glycogen more quickly). Polysaccharides should be eaten later. Generally, it’s recommended to eat protein between 30 minutes to 2 hours after the physical activity. The carbohydrates are, however, more important and so it’s good to eat those first. An exception might be, for example, drinking a protein drink that contains carbohydrates. And it’s again good to consume protein in smaller portions and more frequently.

Did you know?

Protein is the only macronutrient that isnt stored in the body for later use. Our bodies use only the amount of protein they need in that moment and the rest leaves the body in the form of nitrogenous substances in urine. Excessive protein intake won’t make your muscles grow more but rather it’ll put strain on your kidneys. If you eat only proteins after training, the body will transform the proteins into carbohydrates by a process called gluconeogenesis, as the carbohydrates are what the body need