Increase Performance and Prevent Muscle Loss

• How to Use Energy Gels for a Successful Race

Introduction

One indispensable component of marathon preparation is energy gel, a crucial supplement for sustaining performance throughout the race. Effective pacing and endurance require an adequate energy supply, leading many athletes to consider how many gels to carry, how frequently to consume them, and when to take them. However, by understanding the fundamentals of energy metabolism and analyzing one's race strategy, determining an optimal fueling approach can become a more systematic process.

Photo credit: Boston Athletic Association

Energy Substrates in Marathon Running

Although running is classified as an aerobic activity, it does not rely exclusively on mitochondrial oxidative metabolism. Rather, glycolysis, the tricarboxylic acid (TCA) cycle, and oxidative phosphorylation operate concurrently, continuously contributing to ATP production. Therefore, the selection of metabolic substrates and their respective pathways of utilization are critical factors in endurance performance.

During marathon running, glycogen undergoes glycolytic breakdown to generate ATP, yielding pyruvate as an intermediate. Under aerobic conditions, pyruvate is shuttled into the mitochondria and metabolized via the TCA cycle and oxidative phosphorylation to maximize ATP yield. However, endogenous glycogen stores are finite, imposing a physiological constraint on sustained energy production. To compensate, the body concurrently oxidizes alternative substrates, including fatty acids and amino acids, to support ATP synthesis.

Limitations of Body Glycogen and Energy Metabolism

The liver of an average adult male stores about 100g of glycogen, while muscles contain approximately 400g, totaling around 500g. A trained athlete, with proper nutrition, may store an additional 10-20% of glycogen. This stored glycogen can produce about 2,000 to 2,400 kcal of energy. However, glycogen stored in the liver is primarily used to maintain brain function. Additionally, not all muscle glycogens can be utilized, as the body has evolved to conserve glycogen for emergency situations. Therefore, the energy available from glycogen is limited, meaning the energy produced from glycogen alone is finite.

Additionally, hepatic glycogen primarily serves to regulate blood glucose levels and sustain cerebral function, while muscle glycogen is conserved as a strategic reserve. Evolutionarily, the human body has adapted mechanisms to economize glycogen utilization during prolonged exertion, meaning that the fraction of glycogen readily available for endurance exercise is further constrained.

As a result, the body must mobilize additional energy substrates, such as circulating glucose, free fatty acids, and amino acids. However, when marathon pace approaches the second lactate threshold (LT2), metabolic reliance shifts toward glycolytic and anaerobic pathways. Because lipid oxidation necessitates additional oxygen, its contribution to energy metabolism becomes progressively limited at higher intensities. Consequently, one of the body’s compensatory mechanisms involves catabolizing skeletal muscle proteins to derive amino acids for energy production—an undesirable outcome for endurance athletes.

Carbohydrate Supplementation and Performance Enhancement

An alternative strategy to mitigate muscle catabolism and sustain endurance performance is exogenous carbohydrate supplementation via energy gels. These formulations are designed to deliver rapidly absorbable carbohydrates with minimal gastrointestinal distress, facilitating prompt ATP resynthesis. Consequently, energy gels play a pivotal role in maintaining race pace, delaying neuromuscular fatigue, and preserving glycogen stores.

Photo credit: Morten

For instance, Eliud Kipchoge’s world record-setting performance at the 2018 Berlin Marathon was supported by a nutritional strategy incorporating both energy gels and sports drinks, allowing him to ingest approximately 100g of carbohydrates per hour, totaling around 200g throughout the race. The benefits of carbohydrate supplementation extend beyond elite runners. A 2013 study conducted at the Copenhagen Marathon demonstrated that amateur runners who consumed three energy gels per hour achieved, on average, a 4.7% faster finish time compared to non-supplemented participants.

Furthermore, contemporary energy gel formulations often include adjunctive ingredients such as electrolytes, amino acids, and caffeine, further optimizing metabolic efficiency and neuromuscular function during prolonged exercise.

Optimal Energy Gel Intake: How Much is Needed?

The appropriate intake of energy gels depends on both the duration and intensity of exercise. Sports nutritionist Asker Jeukendrup recommends carbohydrate consumption of up to 90g per hour for endurance activities exceeding three hours in duration. Given that most commercially available energy gels contain approximately 25-30g of carbohydrates per serving, this translates to an intake of approximately three gels per hour.

Photo credit : runandbecome.com

However, these recommendations primarily apply to scenarios in which athletes sustain a pace near LT2 for an extended period. If exercise duration is relatively short and endogenous glycogen stores are sufficient, or if exercise intensity is low enough to permit substantial reliance on lipid oxidation, frequent energy gel supplementation may not be necessary. Therefore, fueling strategies should be individualized based on metabolic demands, race duration, and pacing strategy.

Should You Use Energy Gels?

In conclusion, marathon racing at a competitive pace necessitates energy gel supplementation, not only to sustain performance but also to mitigate muscle degradation. When running at an intensity near LT2 for an extended duration, glycogen depletion accelerates, prompting the body to conserve its remaining reserves. Consequently, in the absence of exogenous carbohydrate intake, muscle protein catabolism may increase as a compensatory energy source.

Thus, energy gels serve a dual function: they provide a readily available energy source to sustain race performance and prevent muscle degradation. Instead of relying on excessive post-race refueling, strategic in-race carbohydrate supplementation can enhance performance outcomes while preserving skeletal muscle integrity.

References

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