DURING THE RACE: HOW MUCH CARBOHYDRATES

Consuming additional carbohydrates during the marathon has a number of positive effects that together lead to better performance and a faster time. During the race there is no need for other macronutrients (protein, fat) as only carbohydrates are present in limited quantities and are the best source of energy.

Recommendations for how much carbohydrate you should consume vary between 30g and 90g per hour. For most people, a moderate carbohydrate intake of 60g per hour is enough to boost performance, and although this is a moderate intake, these amounts should be practiced before the race. You should avoid delaying your carbohydrate intake until you feel tired and should begin early in the race with regular meals every 15 to 30 minutes, as desired.

For anyone who runs very quickly and with high intensity, an intake of up to 90 g per hour can make sense, as at higher running speeds more carbohydrates are needed for energy. This large amount of carbohydrate must contain fructose in addition to glucose, as 90 g of glucose per hour cannot be absorbed and leads to gastrointestinal problems.

Therefore, it is best to use a multi-transportable carbohydrate as a carbohydrate source, such as a 2:1 ratio of glucose to fructose. Such a high intake is not for everyone and should be reserved for relatively experienced marathon runners who run relatively fast.

WHAT IS THE BEST SOURCE OF CARBS FOR A MARATHON?

There is a wide range of food and drink options to help you consume carbohydrates during the marathon, including drinks, gels, chews and bars. All sources are similarly effective at providing carbohydrates, although each has different specific considerations.

Drinks are very popular and can be available ready to drink or as a powder that you can mix yourself. Carbohydrate concentration is worth considering because drinks with very high carbohydrate concentrations can slow gastric emptying, causing discomfort and also limiting carbohydrate absorption. If the concentration is too low, very large amounts of fluid have to be consumed in order to obtain enough carbohydrates, which increases the urge to urinate. An ideal sports drink should have a carbohydrate concentration of 6-7%.

Energy gels have a very high carbohydrate content (+/- 30%), which means that if consumed without water they can cause stomach upset and bloating. Because they are so compact, it is important to consume liquids in addition to gels. Gels have the advantage of being quite easy to consume compared to large amounts of carbohydrate-containing drinks or foods that require chewing.

Bars are very different and can contain very different amounts of carbohydrates, fat and fiber. Therefore, it is important to check the nutritional information before choosing bars. Choose energy bars that are low in fat, fiber and protein and that are quick and easy to digest. Bars have the advantage of preventing the feeling of hunger or empty stomach that often occurs towards the end of a race. However, they can be difficult to chew and swallow while running.

Some bars have a very high carbohydrate content (e.g. 60g), which can meet your carbohydrate needs for an entire hour. Therefore, it may be best to divide the bar into regular portions every 15 to 30 minutes to ensure consistent carbohydrate intake. This high carbohydrate content makes them an efficient way to transport lots of carbohydrates.

Chews offer some of the benefits of gels in that they are high in carbohydrates with minimal or no protein, fat or fiber and must be consumed with liquid due to their high carbohydrate concentration. Like bars, they need to be chewed, which can be difficult when running.

The key when choosing carbohydrate sources during the race is to choose options that are comfortable for you and that you have practiced. When it comes to carb intake, all options are similar - but assuming you're consuming the right amount of carbs, how you do it will depend on your personal preference.

A WORD ABOUT FOOD STATIONS

Some races may have food stations that often contain foods that you are not used to and have not practiced with - and may also include foods high in fat, fiber or protein. It is often possible to find out what is available at the aid stations and whether these foods or drinks are suitable or if you need to bring your own.

FLUID AND HYDRATION

Dehydration is a potential cause of fatigue during a marathon, as water is lost through sweat to maintain normal body temperature and through breathing. Running faster leads to more heat production and therefore more sweating. In hot conditions this is exacerbated as the body attempts to lose more heat.

Losing too much water can cause dehydration, making it more difficult to maintain a normal body temperature. Some degree of dehydration is not a problem, but a loss of 3% of body weight or more can negatively impact performance. It is important to drink enough fluids at the start of the race and to stay hydrated after the start.

Aiming to consume slightly less fluid than you lose through sweat is good practice because longer races are closer to your sweat rate. For slower runners, drinking to your thirst level is a good strategy, although faster runners may benefit from a dedicated plan. Most carbohydrate drinks contain sodium and other electrolytes that are lost with sweat. Consuming these electrolytes can support fluid absorption.

Since your gastrointestinal tract is less able to absorb carbohydrates and liquids later in the race, it is best to start with liquids and carbohydrates at the beginning of the race. You should expect to lose some weight over the course of the race (perhaps 1 to 2 kg), which is a mixture of glycogen and water. It's important not to drink too much fluid while racing, as this can lead to a potentially fatal condition called hyponatremia.

Use common sense when deciding how much fluid you should drink and ensure you do not gain weight over the course of a race as this would indicate possible hyponatremia. If you experience gastrointestinal symptoms such as bloating or bloating, you can help by stopping fluid and carbohydrate intake and temporarily reducing your running speed to allow your stomach to empty and absorb the fluid and carbohydrates.