Many runners are able to maintain good performance until 25 or 30 km but experience a significant pace drop during the final part of the marathon. This loss of performance, commonly known as “hitting the wall”, is usually related to low carbohydrate availability, dehydration, poor pacing strategy, and accumulated muscular fatigue.
Performance decline in the final kilometers is one of the biggest challenges faced by endurance athletes. Even well trained runners may experience an important reduction in performance when nutrition strategy, hydration, and effort distribution are not properly aligned.
What Causes a Runner to “Hit the Wall” in a Marathon?
The reduction in pace during the final part of the race happens due to a combination of physiological and metabolic factors. The main ones include muscle glycogen depletion, fluid and sodium loss through sweat, neuromuscular fatigue, and a progressive increase in perceived exertion.
During a marathon, the body mainly uses carbohydrates and fat as energy sources. However, glycogen stores are limited. When carbohydrate intake during the race is insufficient, the athlete may experience the so called “wall”, characterized by intense fatigue, abrupt pace reduction, and difficulty sustaining intensity.
In addition, progressive dehydration reduces cardiovascular efficiency and impairs body temperature regulation, especially in hot race conditions.
Carbohydrate Strategy: One of the Most Important Factors
Adequate carbohydrate intake before and during the race is one of the main strategies to avoid performance decline in the final kilometers.
Current scientific literature recommends an intake between 60 g and 90 g of carbohydrate per hour during long endurance events. In practical marathon strategies, this means carbohydrate intake during the race usually follows a range of 60 g/h ≤ carbohydrate intake during the marathon ≤ 90 g/h, and may exceed these values in athletes with proper gut training and good gastrointestinal tolerance.
The use of multiple carbohydrate sources, such as maltodextrin and fructose, promotes greater intestinal absorption and better energy availability throughout the race.
Another important point is avoiding waiting for fatigue signs before starting carbohydrate intake. Energy supply should begin early in the race, in a planned and consistent manner.
Hydration and Sodium Replacement Influence Performance
Progressive dehydration increases body temperature, raises perceived exertion, and reduces the ability to sustain pace.
For this reason, individualized hydration strategies are essential, especially for athletes with high sweat rates or elevated sodium loss.
Many runners focus only on water intake, but electrolyte replacement is also essential for maintaining muscle function and fluid balance. In long and hot races, sodium deficiency may increase the risk of early fatigue, performance decline, and muscular discomfort.
Athletes who show white salt stains on clothing, very salty sweat, or frequent muscle cramps usually require greater attention to electrolyte replacement.
Poor Pacing Accelerates Fatigue
One of the most common marathon mistakes is starting the race above a sustainable pace.
The first kilometers usually feel easier, which often leads runners to go faster than planned. This accelerates glycogen consumption and increases muscular fatigue earlier in the race.
Smart effort distribution throughout the marathon is one of the most effective strategies to avoid major pace decline in the final kilometers.
Maintaining pace consistency, respecting effort zones, and controlling speed from the beginning can lead to more efficient performance in decisive stages of the race.
Gut Training Also Impacts Performance
The gut also needs to be trained during marathon preparation.
Many athletes experience gastrointestinal discomfort when increasing carbohydrate intake during races simply because they did not practice this strategy during training.
Gut training improves gastrointestinal tolerance, nutrient absorption, and the ability to utilize larger amounts of carbohydrate without symptoms such as nausea, abdominal distension, or gastrointestinal discomfort.
For this reason, race nutrition strategies should be tested during long runs and adjusted individually.
Practical Applications for Marathon Runners
Some practical strategies may help reduce pace decline during the final kilometers:
Before the Race
- Follow an appropriate carbohydrate strategy in the days before the event
- Adjust hydration and sodium intake according to individual characteristics
- Avoid starting above planned pace
During the Race
- Start carbohydrate intake early
- Consume carbohydrates in divided doses throughout the marathon
- Combine hydration with electrolyte replacement
- Monitor pace and perceived exertion
During Preparation
- Practice race nutrition strategies during long runs
- Train the gut to tolerate higher carbohydrate intake
- Simulate race conditions, especially heat and hydration demands
Conclusion
Avoiding pace decline in the final kilometers of a marathon depends on a combination of physiological, nutritional, and strategic factors. Adequate carbohydrate intake, fluid and sodium replacement, pacing control, and gut training are key pillars for maintaining performance until the finish line.
Each athlete has individual needs, and personalized strategies tend to produce better results both in performance and tolerance during competition.
