You start the race feeling good, find a comfortable pace, and feel like you can maintain it for a long time. But as the kilometers go by, your speed starts to drop. The effort feels harder, your legs get heavier, and maintaining the same pace becomes increasingly difficult.
This happens because fatigue during long races is the result of several factors, not simply a lack of energy.
Fuel availability starts to matter
During prolonged exercise, the body uses carbohydrates and fat as sources of energy. The higher the intensity, the greater the contribution of carbohydrates tends to be.
The problem is that glycogen stores are limited. As the race progresses, reduced carbohydrate availability can make it harder to maintain high intensities.
That is why, during long races, carbohydrate intake can help maintain energy availability and support performance.
Muscle fatigue builds up
It is not only about fuel. As time goes on, the muscles also accumulate fatigue.
The ability to produce force and maintain efficient muscle contraction can decrease. As a result, the athlete needs to work harder to maintain the same pace they were holding earlier in the race.
That is why the final kilometers can feel so different from the first ones, even when the speed has not changed significantly.
Perceived effort increases
As fatigue builds up, perceived effort also increases.
The brain integrates information related to muscle activity, body temperature, cardiovascular function, and energy availability. As a result, an intensity that felt comfortable at the beginning can become much harder toward the end.
This increase in perceived effort also contributes to a drop in pace.
Heat and hydration also matter
In hot environments, the challenge becomes greater. The body needs to dissipate the heat produced during exercise while maintaining adequate blood flow to the muscles.
Fluid loss through sweat can further increase cardiovascular strain. Sweat also contains sodium and other electrolytes, and the amount lost varies considerably between athletes.
Therefore, during long races, hydration and electrolyte strategies should take into account duration, temperature, sweat rate, and individual characteristics.
And starting too fast can make everything worse
Another common factor is pacing.
Starting faster than planned may feel easy during the first few kilometers, especially because the athlete is rested and has not yet accumulated much fatigue. But that initial effort comes at a cost.
Higher intensity increases energy expenditure and accelerates the development of fatigue, making it harder to maintain the pace later on.
In long races, running well does not simply mean running fast. It means distributing your effort intelligently.
How can you avoid such a large drop in pace?
The strategy starts before race day.
Practicing race pace, planning carbohydrate intake, testing hydration and electrolyte strategies during training, and avoiding an overly fast start are some of the ways to improve your ability to maintain your pace.
And there is one important detail: your nutrition strategy also needs to be practiced. Race day is not the time to test a new gel or an amount of carbohydrate your body has never experienced during exercise.
Conclusion
Your pace drops at the end of a long race because different mechanisms of fatigue accumulate over time. Carbohydrate availability decreases, muscles become less efficient, perceived effort increases, and factors such as heat, hydration, and pacing can make the decline even greater.
Therefore, improving your performance in the final stages does not depend on a single strategy. It is the result of training, pacing, and a well-planned nutrition and hydration strategy.
