Many people in Germany practice endurance sports to keep fit and to create a balance to everyday life. The majority of athletes train for a marathon or other long-distance sporting event and, in addition to their training plan, also pay attention to a suitable diet in order to achieve the best possible performance during the competition. A diet adapted to an endurance sport can bring about some performance-optimising aspects. These include covering the high energy requirements during endurance performance, the carbohydrate-rich diet that is so essential for endurance sports, covering the athlete’s increased water and electrolyte requirements and an increased vitamin supply.
Energy requirements for various endurance sports
During heavy physical work, the amount of energy required is often already over 3500 kcal (kilo calories) per day. And even in endurance sports these values are sometimes far exceeded. Nowadays, a 90-minute ice hockey training session requires about 5000 kcal.
In endurance sports, the figure is considerably higher. The Wasa run, a cross-country skiing over 85 km, is calculated at approx. 8800 kcal.
In the Tour de France, an average mountain stage is calculated with about 9000 kcal and a 24-hour bicycle race over 700 km is calculated with almost 20000 kcal. The necessary energy is mainly provided by liquid food concentrates and the human energy reserves from the fat pads. In ten kilograms of human fat there are about 70000 kcal of energy reserves slumbering, which serve as the main supplier of energy during long-term stress.
Such long endurance strains are hard work for the body and it is not uncommon for red blood cells and muscle cells to be destroyed during competitions such as the ultra marathon. From the theory, energy requirement values are supplied, according to which one can orientate oneself. For endurance loads, 75 kcal are calculated per kg body weight. The recommended dietary composition is 60 percent carbohydrates, 25 percent proteins and 15 percent fats. These values can serve as a rough orientation, but they can also vary greatly depending on the length of the endurance exercise.
Required carbohydrate-rich food
An important aspect of endurance training is a diet rich in carbohydrates. A high content of glycogen in the muscles extends the duration of work and also requires sufficient carbohydrates to replenish and supply the stores again and again. Typical endurance sports in which carbohydrates form the basic diet are cross-country skiing, long-distance running, cycling and swimming.
But team sports such as football, handball or hockey also require a high level of carbohydrates. Especially before endurance sports, it is recommended to eat carbohydrate-rich food, as otherwise “lack of fitness” can occur during competition. This is due to the fact that the body cannot store very much glucose that it obtains from carbohydrates (450g).
In addition, a rapid drop in the glucose concentration in the blood due to endurance stress leads to fatigue, which then significantly reduces performance. Above all, the blood sugar level is an important indicator of performance. A measure of how quickly or slowly the blood sugar level rises or falls is the glycaemic index.
Foods rich in carbohydrates are quickly converted into sugar after consumption and transferred to the blood. The faster this process takes place, the higher the glycemic index of the respective food (and vice versa). Glucose is given a glycemic index of 100 as a reference value for better comparison.
Especially at the end of an endurance exercise and immediately after a long exercise, it is important to eat foods with a high glycemic index. White bread, sugary drinks, honey and potatoes, for example, have a high value for apples, while yoghurt and milk have a low glycaemic index. The 60 percent carbohydrates in the diet per day recommended for endurance athletes mean a carbohydrate intake of up to 800 g. The advantages of the high carbohydrate content are increased endurance performance due to the high energy supply by glycogen in the muscle cell, an up to ten percent higher energy yield per litre of oxygen compared to fats and proteins, and a low digestive capacity because carbohydrates are easy to digest.
However, a carbohydrate-rich diet also has disadvantages. Athletes with a high carbohydrate content in their diet tend to suffer more quickly from diarrhoea due to increased fermentation in the intestine. In addition, a high-carbohydrate diet involves a large amount of food, as these foods often have a high proportion of water and cellulose. To avoid these problems, athletes usually get a nutrient concentrate in liquid form with a high carbohydrate content.