The 5 Best Reasons Why Fluid Matters In Marathons

Water has many important tasks in the body; it acts as a carrier of nutrients and waste products as well as a thermostat. The daily fluid balance regulates with an average separation/absorption on 2-3 liters of water. By running, the body separates more fluid mainly as sweat. Fluid/sugar solution Improves your Performance and is crucial particular on the marathon distance, and you cannot trust that your thirst sensation tells you when you have to drink. If you feel thirst, you are already very likely to be dehydrated. The 5 best reasons why Fluid matters in marathons are about how to maintain your fluid balance in a marathon race.


What Does Fluid Loss Mean For The Performance?

A fluid loss of 2% of the total body weight has a negative effect on physical performance. At 3-5 % weight loss through fluid loss, your performance reduces by 40 to 50 %. An additional fluid loss will lead to severe dehydration, where muscle coordination and the ability to think clearly decrease.

Some of us remember the episode with severe dehydration as Gabrielle Andersen-Schiess suffered from it. We saw on TV when she approached the finish line by the women’s marathon race at the Olympics in 1984 in Los Angeles. She had completely lost control of his movements and staggered over the line.


Check your Fluid Loss

A good way to check, how much fluid loss you suffer from under various temperature conditions, is to weigh yourself before and after the long training runs LSD. The difference in weight indicates the fluid loss. Thus, one kg of weight loss means that you have lost one liter of fluid.

In this way, you have a measure of how much fluid you lose in a cold and hot climate, you can hereby calculate how much you have to drink during the run to avoid dehydration. As a rule of thumb, you can expect that the performance reduces by 10 % for each 1% fluid loss.

If your weight is 70 kg, you contain about 45 liters of water. A fluid loss of 4.5 kg will then reduce the performance to zero. When I ran my first City marathon several years ago in a very hot environment, my body weight before the start was 74 kg and just after the race, it was 70 kg.

Besides it was the fastest weight loss in my life, I had my challenges during the last kilometers, since the body comes in fluid deficit and cannot get rid of the heat by sweating, the temperature rises and the body begins to overheat, so I had to slow down the pace pretty much.

I was walking/jogging on the last kilometer and it was not one of my funniest experiences. In fact, that was one of my bigger lessons as a runner.

The 5 Best Reasons Why Fluid Matters In Marathons weight Scale

Your Body’s Heat Regulation Moves The Fluid Balance

When you run the body temperature rises because the muscles need for Oxygen increases. This increased Oxygen needs covers by sending more blood through the blood circulation system per minute. The amount of blood is of course the same, so the larger minute volume is the result of a faster heart rate and a larger stroke volume.

The blood’s greater speed brings greater friction in the blood vessels and together with the greater cell activity in the muscles, leads to the body’s temperature rising. To avoid heatstroke, the body seeks to get rid of the excess heat by sweating.

The regulation of heat occurs predominantly by the body’s giving off the heat through evaporation. Evaporation takes place from the exhaled air and by the skin, which delivers heat to sweat that evaporates from the skin’s surface. Hereby cools the skin and there is room for “new” sweat on the surface, which again evaporates and the process is moving.

Negative fluid balance  – compensate for the sweat loss

If the runner does not compensate for the sweat loss with fluid intake, it will gradually become more difficult for him to keep the body temperature down. Fluid loss and increased body temperature mean that fluid from the blood (blood plasma) squeezes out of the bloodstream.

Thus, the blood becomes thicker and the heart cannot be filled adequately, which leads to decreased stroke volume and minute volume.

Therefore, the heartbeat increases to satisfy the muscle’s Oxygen demand. When the heart rate gets closer to the maximum heart rate, it will be difficult to keep the same performance level over a longer time.

The Runner’s judgment and performance reduce while running speed and coordination ability decreases. If he doesn’t consume fluid, the situation can become life-threatening and end with a heat stroke.

If you consume fluid during a competition or training, you will avoid dehydration and be able to endure longer or be able to keep a bit higher intensity. How much fluid/sweat you lose in the long runs, will vary depending on the work intensity.

Likewise, body weight, clothing and climate conditions as the amount of solar, wind and humidity also have an impact on how large the fluid loss becomes.

Fluid Intake In Long Distance Running

As you see, you should cover the fluid loss by drinking during the run. In races, there are very often fluid stations every 5 km. In training there are special fluid belts; you can buy to bring fluid with you on particular the long training runs. However, it’s not simple to meet the fluid loss completely.

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To some degree, the fluid loss can be replaced if you drink water, but the body is unable to absorb more than 1 liter per hour in warm environments and 1,2-liter water per hour in cold environments.

The fluid intake may be as water or energy drink, with carbohydrates and a little salt added to the water. The salt stimulates fluid absorption. To maintain the fluid balance, it’s better to drink clean water, because the body absorbs up to twice as much fluid from clean water than from water containing carbohydrates. However, it will still be a benefit to drink a certain quantity of energy drink to maintain the concentration of glucose in the blood.

Positive fluid balance between clean water and sugar solution

When running a marathon race in a warm environment, the choice of clean water and energy drink can therefore be difficult to balance. In one way, you would like to absorb as much water as possible, but on the other hand, you also want to maintain the glucose concentration in the blood.

At the same time decreases the body’s ability to absorb carbohydrate from the energy drink with warmer environments where the water uptake alone reduces with about 20%. Hereby you must drink even more energy drink to receive the same amount of carbohydrates as in cooler environments.

Nor can you just increase the concentration of carbohydrate in the energy drink, because the body absorbs the fluid much slower at higher carbohydrate concentrations than 5 – 7 %. To prevent dehydration and low glucose concentration in long-distance races, you have to drink water or energy drink from the start and then drink as often as you can.

In virtually every major marathon race today, there are fluid depots located on the route at each 5 km, and it is better to drink a small amount at shorter intervals than the opposite.


Running In Different Environments And Fluid Balance

In hot environments should the fluid loss covers by water, since it is absorbed faster and easier by the body compared with a sugar solution. In return, you must expect a decrease in the performance, because the carbohydrate depots soon will be insufficient, when not supplemented with sugar solution.

In cooler environments below 20 degrees Celsius, you can cover both fluid loss and at the same time supplement the carbohydrate depots with a sugar solution of about 6 %.

If you want to complete a long-distance race of more than 1 hour like a marathon race, it is also important with training in drinking to get used to having fluid in the stomach during the race and to train the body to absorb fluid during longer and more demanding races.

With a marathon race as the goal, it becomes very important. It is too late to find out in the actual marathon race, that you become poor of the sugar drink and you cannot drink from the bottle or cup without getting it stuck in the throat, since the breathing is faster during the race.

Fluid Balance Is Often a Choice

Since it’s very important with fluid intake in long-distance running it can also be a balance between a sugar solution and clean water. In my opinion, your health is most important. So, stay to the water and don’t go for a personal record when dehydration is a risk factor.

I hope you like this review and if you have any questions about this topic about Fluid Balance or want to leave your own Personal review, please leave a comment below.

What is the best thing to drink during a marathon?

Water and sports drinks are both good fluid sources. If you run for less than an hour, plain water is a good choice, but, if you run for longer than an hour like a marathon race, drinks containing sugar help to fill your carbohydrate depots.

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6 thoughts on “The 5 Best Reasons Why Fluid Matters In Marathons”

  1. I had no idea A fluid loss of 2% of the total body weight has a negative effect on the physical performance while a fluid loss of 4.5 kg will then reduce the performance to zero. It is very important to stay hydrated as fluid increases performance of the body.

    Thanks for sharing this educating piece with me 

  2. helllooo dear, i a really gratefull with such an amazing post you have shared with us so far, your site really is full of such an amazing post, i must say i have been saving each of your pages to learn alt from these article, it really has been an interesting content, cant wait to show my fiends, ill surely share your contents on my social media page.

  3. During exercise, the main way the body maintains optimal body temperature is by sweating. … Drinking fluid during exercise is necessary to replace fluids lost in sweat. This action will reduce the risk of heat stress, maintain normal muscle function, and prevent performance decreases due to dehydration. Fluid intake is necessary for optimal performance when running.


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