Carbohydrates and Fueling Your Athletic Performance
What You Will Learn
How the body uses carbohydrates as its main energy currency and why carbohydrates are the only fuel source capable of meeting high-intensity demands.
An inside look at how carbohydrates are stored as glycogen, its function, where it is located, and its role in creating explosive power.
Why cutting carbohydrates can lead to muscle loss and how adequate carbohydrate intake protects retention of muscle mass.
How to distinguish between different types of carbohydrates to manage energy levels and avoid the mid-workout crash.
Evidence-based protocols for fueling before, during, and after training to maximize performance and accelerate recovery.
In the landscape of modern sports nutrition, carbohydrates are perhaps the most misunderstood and unfairly judged macronutrient. This widespread misinformation often leads athletes toward restrictive dietary patterns that inadvertently limit their physical potential and inhibit progress in the pursuit of their true athletic potential. When you view carbohydrates through a lens of misconception rather than as a functional fueling tool, you limit the very energy source required to train and compete at an elite level.
While you don’t need to become a nutrition expert to reach your goals, a foundational understanding of how nutrition fuels output is a non-negotiable requirement for the athlete who aspires to train and perform at a high level. In an environment where every edge matters, optimizing your carbohydrate intake is likely the most significant performance advantage you are currently leaving on the table. To move from just eating throughout the day, to intentionally executing performance nutrition principles, you have to look at the process of how the body actually produces energy during your training and competition.
Carbohydrates and Energy Production
To appreciate why carbohydrates are so important, we have to first look at the specific metabolic pathways the body uses to create adenosine triphosphate (ATP), which serves as the universal energy currency for every muscle contraction. Your body does not store a large amount of ATP. Instead, it must constantly regenerate it through three primary energy systems: the phosphagen system, the glycolytic system, and the oxidative system.
To provide a complete picture of these energy systems, we’ll begin looking at the phosphagen system (or the ATP-PC system), which is your body's immediate energy source for explosive movements. This system relies on stored ATP and phosphocreatine (PC) already present within the muscle cell (Click here to read more on the role of creatine supplementation for athletes). Because it doesn't require oxygen or the process of glycolysis, it can regenerate ATP at an even faster rate. However, its capacity is extremely limited, typically providing enough energy for only about 5 to 10 seconds of all-out effort.
As the energy stores of this system are depleted during those first few seconds of activity, the body begins to transition heavily into the glycolytic system to generate energy. While the oxidative system is highly efficient for low-intensity, steady-state activity, it lacks the rate of production required for sprinting, jumping, or rapid change of direction because it requires oxygen to break down fats and carbohydrates. In contrast, the glycolytic system—which is the dominant energy provider for activities lasting between 30 seconds and two minutes—operates anaerobically, or in the absence of oxygen. In this process, your body breaks down glucose through a series of enzymatic reactions. This pathway is significantly faster than oxidative phosphorylation, allowing for the rapid regeneration of ATP necessary to maintain high-intensity efforts. Because carbohydrates are the only macronutrient capable of being broken down via glycolysis, they are the only fuel source that can support the high power-output demands of competitive sport (Kantern & Luke, 2021).
Carbohydrates and Stored Energy
Carbohydrates that are not immediately utilized for energy are stored in the form of glycogen, a large, highly branched polymer of glucose. Your body primarily maintains these stores in two locations: the skeletal muscle and the liver. Muscle glycogen is a localized energy reserve, used specifically by the muscle in which it is stored, while liver glycogen is responsible for maintaining stable blood glucose levels to fuel the central nervous system.
The branching structure of glycogen is a vital evolutionary adaptation for athletes. Because the molecule has many open ends, enzymes can create multiple glucose molecules simultaneously through a process called glycogenolysis. This allows for a massive, instantaneous flood of glucose into the glycolytic pathway when an athlete is training or competing.
In terms of capacity, the average well-trained athlete can store approximately 400 to 600 grams of glycogen, with the vast majority (about 80%) residing in the skeletal muscles. However, these stores are limited. As you approach glycogen depletion, the body can no longer sustain high-intensity glycolysis, and your body is forced to rely on the much slower process of fat oxidation (an energy process mentioned previously). This shift results in a drop in mechanical power and technical proficiency, resulting in noticeable reductions in your athletic performance (Murray & Rosenbloom, 2018).
Types of Carbohydrates: Simple and Complex
It is helpful to view carbohydrates through the lens of their chemical structure and impact on blood glucose levels. We generally categorize them into two main groups: simple and complex.
Simple carbohydrates, like fruits, honey, gummies, sports drinks etc., are characterized by their rapid digestion and absorption. These are strategically useful when immediate energy is required and glycogen stores are approaching depletion.
In contrast, complex carbohydrates like potatoes, whole grains, vegetables, etc., contain longer chains of sugar (glucose) molecules that require more time for the body to break down. This slower digestion provides a more sustained release of glucose into the bloodstream, which is preferable for maintaining energy levels during non-training hours and preventing the fluctuations in insulin that can lead to premature fatigue.
Protecting Your Muscles
One of the most frequent misconceptions in sports nutrition is that protein alone is responsible for muscle preservation. In reality, carbohydrates play a vital muscle sparing role. When an athlete maintains a chronic carbohydrate deficit while training at high intensities, the body may initiate gluconeogenesis to produce the glucose required for central nervous system function. This process often involves the breakdown of existing muscle tissue to provide the necessary amino acid precursors for energy. By ensuring adequate carbohydrate intake, the athlete protects their lean muscle mass, allowing dietary protein to be utilized for its primary purpose of tissue repair and hypertrophy rather than being burned as a suboptimal fuel source (Burke et al., 2018).
Best Practices for Carbohydrate Timing and Restoration
Strategic timing allows us to maximize the performance benefits of carbohydrates while maintaining metabolic health.
Pre-Training:
2-3 Hours Out: Prioritize a meal focused on complex carbohydrates like oats, rice, or sweet potatoes. These slow-digesting sources provide a steady release of glucose into the bloodstream, ensuring your energy stores are topped off and your blood sugar remains stable as you begin your session.
0–60 Minutes Out: Priority shifts towards simple, fast-acting carbohydrates. During this time, a small snack such as a banana, a spoonful of honey, or a specialized sports drink provides a rapid spike in blood glucose that is immediately accessible for the central nervous system (brain) and the working muscles.
Intra-Training: For sessions lasting longer than 60-minutes, the introduction of fast-acting, simple carbohydrates can help maintain blood glucose levels. This support to the central nervous system helps delay the onset of fatigue and maintains technical proficiency during intense training and performance. Ideally this comes in the form of a source that is easily accessible like a sports drink or apple sauce pouch.
Post-Training: The period immediately following training is most critical for restoring depleted glycogen stores. Since every gram of glycogen stored is accompanied by roughly three grams of water, this restoration is essential for cellular hydration and overall recovery (Fernández-Elías et al., 2015). Pairing carbohydrates with a high-quality protein source during this time accelerates the recovery process and ensures the athlete is prepared for their next bout of physical exertion (Ivy & Kuo, 1998).
If you would like to learn more about Performance Nutrition and how you can leverage these skills and behaviors to pursue your true athletic potential, you can access the Premier Nutrition Blueprint by clicking this link: https://www.premierathleticdevelopment.com/the-premier-athlete-system
Again, you don’t have to be a nutrition expert, but you have to possess the right knowledge and skills around your fueling habits if you want to play at the highest level.
References
Burke, L. M., et al. (2018). Fueling strategies to optimize performance: Training and racing. International Journal of Sport Nutrition and Exercise Metabolism.
Fernández-Elías, V. E., et al. (2015). Relationship between muscle water and glycogen recovery after prolonged exercise in the heat. Medicine & Science in Sports & Exercise.
Ivy, J. L., & Kuo, C. H. (1998). Role of insulin and exercise in the regulation of muscle glycogen synthesis. Free Radical Biology and Medicine.
Kantern, M., & Luke, A. (2021). Carbohydrates and Athletic Performance: The Evidence-Based Science. Nutrition Today.
Murray, B., & Rosenbloom, C. (2018). Fundamentals of glycogen metabolism for coaches and athletes. Nutrition Reviews.
Comments