Many people in the UK and around the world participate in endurance sports to keep fit and to provide a balance to everyday life. Much of the athletes trained in a marathon method or other endurance sporting events pay additional note to not just their training plan, but also to an appropriate diet to achieve their best performance at the competition.
Endurance sport nutrition can provide some great performance optimization benefits with it. This includes coverage of the high energy demand necessary during endurance performance namely in the form of food that are carbohydrate rich and suited to endurance sports. There is also an increased fluid intake to meet the water and electrolyte needs of the athlete as well as important vitamin intake.
Energy demand in various endurance sports
In heavy physical activity, the required amount of energy is often in excess of 3500 kcal (kilocalories) per day. Likewise also in endurance sport these values are quite similar also. A 90-minute hockey training session added to a hickey player’s normal day would result in the need of a calorie intake within 4000- 5000 kcal.
In endurance sports the energy demand may be similar or even more. Athletes participating in events such as the Wasa Run (a cross-country skiing event of 85 kilometres) would need to carb-load and could see themselves consuming between 7000-8000 kcal on the day of the event. It is estimated that those who take part in the Tour de France have an average caloric need of approximately 9000 kcal during the peak stages. The necessary energy is usually provided mainly in the form of liquid food concentrates and the human energy reserves from fat deposits.
Did you know: 10 kilograms of human fat = around 70,000 kcal of energy reserves
In competitions such as the ultra-marathon, the red blood cells and muscles cells are exhaustively used and depending on which is more, may determine how you receive additional energy. In endurance exercise it is estimated that 70-75 kcal should be consumed per kg of body weight. The nutritional composition is therefore recommended for endurance athletes as:
60% carbohydrates, 25% protein and 15% fats.
These values can serve as a rough guide, but also vary greatly depending on the length of the endurance exercise and the level of the individual.
Carbohydrates in endurance sports
An important aspect of endurance exercise is a high-carbohydrate diet. A high glycogen content in the muscle lengthens the amount of activity that can be performed without complete fatigue. Carbohydrates are thus necessary to replenish the store repeatedly.
Typical endurance sports, in which carb-loading is common practice include cross-country skiing, long-distance running, cycling and swimming. But team sports such as football, handball, basketball, rugby or hockey also require a high level of carbohydrates for athletes to function adequately. Especially in endurance sports, it is recommended to consume high-carbohydrate foods to avoid any conditional problems that could arise from a lack of energy.
This is because the body does not retain all glucose that is obtained from carbohydrates (max. 450g). In addition, the glucose concentration in the blood usually drops at a rapid rate which can lead to fatigue due to endurance exercises, which in turn can affect performances negatively.
Blood sugar levels are usually an important indicator of performance. Measuring how fast or slow the blood sugar level rises or falls is shown in the glycemic index. Carbohydrate-rich foods are rapidly absorbed after consumption, with the sugar being converted to glucose in the blood. The faster this process is, the higher the glycemic index of the food (and vice versa). Glucose level here is a reference to the glycemic index, with 100 being the highest.
At the end of an endurance exercise or an event needing high levels of stamina it is important to consume foods with a high glycemic index. Examples of some of these include, white bread, sugary drinks, honey and potatoes which have a high value. In contrast foods such as apples, yogurt and milk, in contrast have a low glycemic index. The recommended carbohydrate intake for endurance athletes is 60% in their diet per day, which is usually around 700-800 g.
The advantages of high carbohydrate content include:
- increased endurance capacity due to the high energy supply by glycogen in the muscle cells
- easily digestible and readily available energy
Disadvantages of a high carbohydrate diet however include:
- Increased chance of diarrhoea due to the increased fermentation in the stomach
- Due to the high food consumption there is also a high percentage of water and cellulose leading to excess water in the system
- Costs of maintaining a high carbohydrate diet
To avoid these problems, athletes usually take a nutrient concentrate in liquid form with high carbohydrate content.
The role of fats in endurance sports
Individuals who are training or already are endurance sport athletes should avoid high fat diets, and should not go higher than a 25% daily limit of their nutritional intake of fats. This is because the energy yield of oxygen is very low (as fats are more complex to break down compared to carbohydrates) making the effort to recover lost energy much more difficult.
With such a huge demand for energy for endurance athletes, it would be impractical to avoid any kind of fat from their diet. In particular, oils with polyunsaturated fatty acids and milk, which are excellent sources of fat. The fat content in milk is said to be broken down as such that the fatty acids are rapidly absorbed through the intestinal wall.
Protein intake in endurance sports
Most endurance athletes do not pay much attention as to their protein intake. Due to the amount of food that needs to be consumed to reach their calorie quota, protein content is usually present at a reasonable level. Especially in egg, milk and meat, the consumption of these foods would usually mean the dietary of protein requirement is more than met.
Vitamin intake in endurance sports
The intake of vitamins is similarly to that of proteins in regards to endurance sports. There the opinion is also that the increased demand for food also provides for an increased vitamin intake and this is sufficient for endurance athletes, however this requires a complete diet. The vitamins A, E, K and D are usually well covered by food. The B-group vitamins on the other hand, for example B1 and B2, which provide effective breaking down of carbohydrates, may have a slight shortage in some circumstances.
In this case, it is recommended to use vitamin supplements where necessary. Many athletes take vitamin supplements and hope to gain a health or performance-enhancing boost. This is not actually the case, an increase in performance after the use of vitamin supplements usually indicates there was a prior shortage of the vitamins in the body.
Iron is a particularly important mineral for endurance athletes that is normally present in many foods and is required by the body to function effectively. It is essential in the creation of haemoglobin (an essential structure for red blood cell creation). Unfortunately, only 5 -10% of the supplied amount of iron is actually absorbed by the intestinal wall. This is why this mineral is vital for endurance/sports athletes in particular, as it often occurs that a lack of this mineral can lead to iron deficiency anaemia. This reduces endurance capacity, increasing the chance of fatigue and light-headedness.
Water and electrolyte loss
For long endurance activities like a marathon, especially in temperatures below 20 °celsius, athletes can sweat between two to four litres in order to conduct the heat generated by the muscular energy of the body. Thus, the body loses a lot of water and thus electrolytes and nutrients. If these considerable losses in water and nutrients are not replenished, athletic performance can drop as a direct result.
Already water losses from 2-5% of the body weight slow the heart rate, thus reducing the effective circulation of red blood cells to the necessary areas of the body. Water and electrolyte losses during competition must therefore be constantly monitored and replenished as necessary. Water is very important for endurance sports as the majority of the human body consists of water and the thermoregulation function it holds makes it irreplaceable.
General diet rules for endurance sports
Many athletes divide their three main meals into four to eight small meals in order to create an even spacing for the body’s metabolism to function at its peak level. Before a competition or a long training session, digestion should already be completed; therefore athletes rarely eat a big meal just before a sporting activity. Disrupting the digestive processes during a competition can expend more energy than required, therefore lowering the energy needed to perform at the individual’s maximum level.
The last food intake before a workout or competition should be approximately two to three hours beforehand. Before any endurance exercise, the appropriate meal should consist of sufficient carbohydrates so that the glycogen stores are fully replenished. Glucose drinks or water can be taken closer to the time of training as they do not expend any digestive energy.
During the competition, especially those consisting of movement for more than 10 kilometres require sufficient liquid supply. The liquid ingested should have at least 5% sugar content and should not be drunk all at once. A good example of this is isotonic drinks such as Lucozade sport, Gatorade or Powerade. Any fluid should be taken in intervals so that the fatigue limit can be pushed backwards gradually and intermittently.
Even after the race/competition, it is essential to adopt a proper diet to optimally regenerate and prepare the body for the next competition. It is highly recommended after any event to consume carbohydrate and fluid-rich foods. The sugar is absorbed quickly in the stomach and the blood glucose concentration rises again to an acceptable level.
If the body’s carbohydrate reserves are completely drained, it may take up to 24 hours, until they are restored completely again, for this reason the sports athlete should consume between 50-75 grams of carbohydrate every two hours. Approximately 5-7% of the body’s glycogen storage capacity is replenished per hour, which means it can take close to a day until the body has recovered adequately.
The proper selection of foods and a nutritious diet geared towards endurance performance can significantly optimize an athlete’s ability. Not only the type of food is crucial, but the percentage composition is of central importance for any sport requiring high levels of stamina.
- Nih.gov. (2016) Nutrition for endurance sports: marathon, triathlon and road cycling http://www.ncbi.nlm.nih.gov/pubmed/21916794
- (2016). Nutrition for Endurance Athletes 101 http://home.trainingpeaks.com/blog/article/nutrition-for-endurance-athletes-101 .