Optimizing Performance: What is the role of carbohydrates during competition?

October 15, 2025 •

4 min read

Decades of research have shown that carbohydrate intake is the most significant nutritional factor influencing athletic performance. Understanding what is the role of carbohydrates during competition is crucial for athletes aiming to sustain energy levels, delay fatigue, and maintain peak performance when it matters most.

Quick Summary

Carbohydrates are the primary fuel for high-intensity exercise, stored as glycogen in muscles and the liver. Athletes use specific strategies, like carb loading before events and intra-race fueling with simple sugars, to maximize glycogen stores and sustain energy levels, which also supports cognitive function and skill maintenance.

Key Points

Primary Fuel Source: Carbohydrates are the main energy source for high-intensity exercise, with the body storing them as glycogen in muscles and the liver.
Glycogen Loading: For events over 60–90 minutes, pre-competition carb loading is crucial to maximize glycogen stores and delay fatigue, a strategy that should be practiced during training.
In-Race Fueling: During competition, athletes must consume carbohydrates continuously, with intake rates dependent on the event's duration and intensity (30–90+ grams per hour).
Dual-Fuel Advantage: Combining glucose and fructose allows for faster intestinal absorption and higher carbohydrate intake rates during ultra-endurance events, improving fuel availability.
Cognitive and Skill Support: Carbohydrate intake helps maintain blood glucose levels, which is vital for the brain's function, ensuring sustained focus, decision-making, and skill performance under pressure.
Hydration Synergy: Ingesting carbohydrates alongside fluids, particularly via sports drinks with electrolytes, is key for simultaneous energy provision and hydration, especially in high-heat conditions.
Sport-Specific Strategies: Fueling tactics must be periodized and tailored to the athlete's specific sport, considering the difference in demands between endurance, intermittent, and strength activities.

The Central Role of Carbohydrates in Athletic Performance

Carbohydrates are the body's most accessible and preferred energy source, particularly for moderate- to high-intensity physical activity. During competition, the body breaks down carbohydrates into glucose, which is used immediately for energy or stored as glycogen in the muscles and liver. The availability of this glycogen is a primary limiting factor for endurance performance; when these stores are depleted, athletes experience a sudden and dramatic drop in energy, often called "hitting the wall" or "bonking". Strategic carbohydrate intake before, during, and after competition is therefore fundamental to success.

Pre-Competition: Maximizing Glycogen Stores

For events lasting longer than 60–90 minutes, such as a marathon or triathlon, maximizing muscle glycogen stores beforehand is a critical strategy known as carbohydrate loading. The traditional method involves depleting glycogen stores with a few days of low carbohydrate intake combined with exercise, followed by a high-carbohydrate period. However, modern approaches focus on a simpler strategy of tapering exercise while increasing carbohydrate intake for one to three days leading up to the event. The goal is to consume 8–10 grams of carbohydrates per kilogram of body weight per day during this loading phase. This saturates the muscles and liver with glycogen, providing a deep energy reserve.

Foods for Carb Loading: Complex carbohydrates like pasta, rice, potatoes, and whole-grain bread are ideal for meals in the days leading up to an event.
Meal Timing: Consume a carbohydrate-rich meal approximately three to four hours before competition to allow for digestion.
Pre-Event Snack: A smaller, easily digestible snack consisting of simple carbs (like a banana or energy bar) 30–60 minutes before the start can provide a quick boost of immediate energy.

Intra-Competition: Sustaining Performance

Once competition begins, the body relies on both its stored glycogen and carbohydrates consumed during the event to maintain blood glucose levels and delay fatigue. The amount and type of carbohydrate required depend on the duration and intensity of the activity. Continuous intake prevents a crash by providing a steady supply of fuel for the working muscles and brain.

Exercise lasting >60 minutes: For activities ranging from 60 to 90 minutes, athletes should aim for 30–60 grams of carbohydrates per hour.
Exercise lasting >2.5 hours: For ultra-endurance events, intake should increase to 60–90 grams per hour or more. Combining multiple carbohydrate sources like glucose and fructose is highly effective at these higher rates, as they use different intestinal transporters, leading to faster absorption and improved gut tolerance.
Fueling Format: Athletes can use sports drinks, energy gels, chews, or easily digestible foods like bananas or raisins. It is crucial to practice with these products during training to avoid gastrointestinal issues during the actual competition.

The Cognitive and Hydration Connection

The benefits of intra-competition carbohydrates extend beyond just muscle fuel. Glucose is the brain's primary energy source, and low blood glucose can impair cognitive function, affecting decision-making, focus, and skill performance. By maintaining blood sugar, carbohydrate intake helps athletes stay mentally sharp throughout the event.

Furthermore, hydration is intrinsically linked to carbohydrate fueling, as many energy sources come in liquid form. Electrolytes, particularly sodium, are often included in sports drinks to replace losses from sweat and aid fluid absorption. Combining fluids and carbohydrates ensures both energy and hydration needs are met simultaneously, which is especially important in hot climates.

Tailoring Your Strategy to Your Sport

The optimal carbohydrate strategy varies significantly depending on the demands of the sport. Endurance athletes in events like marathons focus on a continuous supply, while team sports require intermittent bursts of energy. Strength athletes have different needs entirely.


Aspect	Endurance Sports (Marathon, Cycling)	Intermittent Sports (Soccer, Basketball)	Strength/Power Sports (Weightlifting)
Fueling Strategy	Continuous intake during events >60 min to delay fatigue.	Fueling during breaks (e.g., half-time) to top up glycogen and maintain skill.	Focus on daily diet; intra-workout carbs for high-volume sessions.
Target Intake (per hour)	30–90+ grams, depending on event duration and athlete.	30–60 grams (via breaks).	15–30 grams for high-volume sessions, not required for shorter workouts.
Best Carb Sources	Gels, chews, sports drinks, and easily digestible foods.	Sports drinks, chews, or easy-to-digest snacks.	Pre-workout snack or sports drink.
Primary Goal	Maximize fuel availability to sustain prolonged, high-intensity effort.	Maintain blood glucose for skill and mental clarity during intermittent high-intensity efforts.	Replenish glycogen to support recovery between intense sets or sessions.

Conclusion: Strategic Fuel for Peak Performance

In conclusion, the role of carbohydrates during competition is multifaceted and critical for maximizing athletic performance. From the multi-day preparation of carb loading to the in-event consumption of fast-acting sugars, carbohydrates serve as the essential fuel for working muscles, the central nervous system, and cognitive function. The specific approach must be tailored to the individual athlete and the demands of their sport, accounting for factors like duration, intensity, and hydration needs. By implementing a well-practiced, periodized carbohydrate strategy, athletes can effectively delay fatigue, sustain peak performance, and ultimately increase their chances of success. For further insights into the science behind sports nutrition, explore resources like the Gatorade Sports Science Institute.

Frequently Asked Questions

Carb loading is important for long races because the body's glycogen stores, which fuel high-intensity exercise, are limited. By maximizing these stores before the event, you can sustain your optimal pace for a longer period and delay the onset of fatigue.

Insufficient carbohydrate intake during prolonged, high-intensity exercise can lead to glycogen depletion. This results in severe fatigue, often called 'bonking,' and forces the body to reduce intensity as it shifts to less efficient fuel sources like fat, impairing performance.

Simple carbohydrates are broken down and absorbed quickly, providing a rapid energy source ideal for consumption during an event. Complex carbohydrates are digested more slowly and offer sustained energy, making them better for pre-competition meals.

Combining glucose and fructose in sports drinks, especially for events over 2.5 hours, is beneficial because they use different absorption pathways in the gut. This allows for a higher rate of carbohydrate intake (up to 90+ g/h) with less risk of gastrointestinal discomfort.

Carb loading is generally not necessary for short events like a 5K, as the body's normal glycogen stores are sufficient for the duration. For shorter events, focusing on a balanced, carbohydrate-rich meal a few hours prior is usually enough.

Carbohydrates are the brain's primary fuel. Maintaining stable blood glucose levels by consuming carbs during exercise helps support cognitive function, improving focus, concentration, and decision-making, which are crucial for competitive strategy and skill execution.

Yes, you should always test your nutrition strategy during training. Practicing with your chosen sports drinks, gels, and foods allows you to train your gut and identify any potential gastrointestinal issues, preventing unwanted surprises on race day.