Running long-distance races or training runs is not easy physically and mentally. Proper fueling and nutrition to support the muscle strength and energy is very important, but often runners don’t realize that proper fueling is crucial to support mental fatigue. If our brain and mind get affected by extreme fatigue, we may have to slow down, or even stop and drop out of the race.
What Causes Mental Fatigue
Lack of food can produce some very negative thoughts and bad attitude, but proper fueling can help us think positive thoughts and improve our race strategies and performance. Glucose is what can support our brain fuel and energy. Glucose is the only fuel the brain uses, unlike our muscle tissue which uses both glucose and fats. The brain also does not store glucose for its energy supply. To function normally, our brain needs a normal blood glucose level. So, what happens to a long-distance or ultrarunner when running for many hours with an increasing demand of glucose? If a long-distance runner does not ingest the required amounts of carbohydrates (glucose) during a long run, hypoglycemia (low blood sugar) sets in. Hypoglycemia can cause central nervous system fatigue, which is the progressive shutdown of the part of the brain that drives the muscles. This will cause negative attitude and lower the performance level. According to some research, 2% of marathon runners, 6% of 50K runners and 11% of 100K runners get hypoglycemia. The symptoms are reduced ability to concentrate, and high feeling of weakness. That is why fueling our body with carbohydrates (glucose) will help support the performance.
The main provider of glucose into the blood is the liver. The process happens directly from its own store of glucose or indirectly from the production of glucose from proteins. Training also helps the liver’s ability to produce glucose from circulating blood lactate. Good training plans according to your goals will also help train the liver to produce glucose. Because the liver is so small compared to the muscle mass and can only store 250-500 calories of glucose, it could never keep up with the muscles’ demand for glucose when exercising hard or run long-distances. For well-trained runners or athletes, this can support 3-4 hours of running at a moderate pace. Also, the muscles are prevented from using too much circulating blood glucose in order to support the brain. Luckily, our muscles have other ways of obtaining glucose, it has a good supply stored in its own tissues and the ability to use fat as a source of energy. The reason why post-run recovery nutrition is important is the supply stored in the muscles can be doubled if post-training carbs are consumed within 30-45 minutes. When tissues increase the rate of glucose usage faster than the liver can produce it, blood levels fall and body function is impaired. In order to prevent brain drain and preserve our mind’s ability to think and strategize effectively especially in an Ultra race, it becomes crucial to ingest enough carbohydrates during the race. If the muscles become fatigued, the brain will reduce the number of muscle fibers activated, and if we continue running, it will cause us to slow down. This is the body’s way of surviving, it will limit our physiological capabilities, but preserve the neurological function of the brain. Exhaustion in this case, may be defined as a decrease in signals from the brain to the muscles, not a direct change in the muscles’ glycogen levels, but central fatigue.
The most common reason why runners decide to stop running and DNF during a race is due to neurological changes in the brain causing mental fatigue. During long-distance runs, the brain’s production of neurotransmitter (a chemical that carries signals from a brain cell to another) serotonin increases steadily. Higher levels of serotonin can cause feelings of tiredness, sleepiness and lethargy. Another side effect of higher levels of serotonin is the drop of dopamine levels (the neurotransmitter responsible for generating feelings of excitement, reward, motivation and pleasure). One way to support the levels of dopamine is to consume some caffeine with the carbohydrates during a long-distance run. Caffeine has been shown to increase the levels of dopamine in the brain, which will help delaying fatigue.
Race Nutrition and Fueling Tips
Make sure you consume and refuel with carbohydrates before you start feeling hungry, tired and exhausted. Our intestine cannot process carbohydrates and deliver them fast enough to keep up with the high rate of usage by muscles. The maximum amount of carbohydrates to ingest is about 1 gram per minute of exercise, ideally every 15-20 minutes to make it easier to process and absorb. Our body cannot absorb more than 240-280 calories per hour, if our body is depleted of carbs, we can’t replenish all the lost amount of glucose. We should consume between 30-60g of carbs per hour, according to our metabolism and running intensity. Only a small percentage of runners can sustain consuming up to 90g of carbs per hour. Runners that have been training well for their race, are able to increase the absorption rate of glucose. To refuel with either gels, sports drinks, energy bars and real food with carbs which are easy to digest and process will support the physical and mental energy levels. Feed your brain and improve your mental fatigue for a better performance in your next long-distance run.
EAT HEALTHY, TRAIN WELL, FEEL GREAT!
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