Why Carbohydrates Are Key for Training & Race Performance

Carbohydrates are at the heart of endurance sport nutrition. Whether you are preparing for a marathon, training for a Hyrox event, or aiming for a new personal best in a 10k, your carbohydrate intake can make the difference between a strong finish and hitting the dreaded wall. This article explores why carbohydrates are so important for training and race performance, how your body uses them, and how to fuel effectively.

Overview: The Role of Carbohydrates in Running

The Food Tank for Energy

Carbohydrates are your body’s preferred source of energy during moderate to high intensity exercise. When you eat foods like pasta, bread, rice, fruit, and oats, your body converts the carbohydrates into glucose, which is then stored in your muscles and liver as glycogen. These glycogen stores act like your internal battery pack – limited but powerful. During training and racing, your muscles tap into this glycogen to sustain pace and delay fatigue.

Key Concepts Every Runner Should Know

1. Glycogen and Performance

Your glycogen stores are finite, typically enough to fuel around 90–120 minutes of steady running. Once depleted, your body switches more heavily to fat for energy, but fat is slower to convert to usable fuel, which is why pace drops and fatigue sets in. This is commonly referred to as “hitting the wall.” Strategic carbohydrate intake before and during a race helps avoid this performance crash.

2. Training Adaptations

Carbohydrate intake isn’t only about race day. Consuming enough during your training programme ensures you can hit your planned sessions with quality. For example, a long run without adequate fuelling may lead to premature fatigue, preventing you from building the endurance you’re aiming for. Similarly, workouts like intervals and tempo runs rely heavily on glycogen for sustained high effort.

3. Recovery and Adaptation

Post-run carbohydrate intake is essential for recovery. After exercise, your muscles are primed to replenish glycogen stores quickly. Pairing carbohydrates with protein not only restores energy but also supports muscle repair, preparing you for your next session.

Step-by-Step: How to Use Carbohydrates for Training and Racing

Before Training or Racing

Carbohydrate loading, particularly before long races such as half marathons or marathons, is a well-established strategy. This involves increasing carbohydrate intake in the 2–3 days leading up to the race to maximise glycogen stores. For shorter runs or daily training, a balanced meal with sufficient carbohydrates a few hours beforehand ensures you start with fuel in the tank.

During Exercise

For runs lasting more than 75 minutes, consuming carbohydrates while running can significantly improve performance. Energy gels, chews, or drinks deliver fast-acting glucose to maintain blood sugar and spare glycogen stores. Aiming for 30–60 grams of carbohydrate per hour is a practical guideline, though elites sometimes train their gut to handle more.

After Training

Recovery nutrition is often overlooked, but the 30–60 minutes post-run is a crucial window for glycogen restoration. Including carbohydrate-rich foods like rice, potatoes, or fruit, alongside protein, accelerates recovery and allows you to train consistently. You can use our Running Calories Calculator to get a sense of your energy expenditure and plan your recovery meals accordingly.

Examples of Carbohydrate Strategies

Energy from carbs for running

Training Day Example: For a 90-minute steady run, start with a bowl of porridge and fruit two hours beforehand. Carry a gel or sports drink if you expect the run to extend beyond 75 minutes. After finishing, refuel with a sandwich and a recovery shake.

Race Day Example: For a marathon, increase your carbohydrate intake for two days prior, focusing on rice, pasta, and bread. On race morning, eat a high-carbohydrate breakfast three hours before the start. During the race, plan to consume gels at regular intervals (e.g. every 30–40 minutes) to sustain energy and avoid glycogen depletion.

Frequently Asked Questions

Do I always need carbohydrates for short runs?

For runs under 60 minutes at an easy pace, your body typically has enough stored glycogen to fuel the effort without additional intake. However, starting the run well-fuelled helps maintain quality, especially if you are training twice in a day.

What about low-carbohydrate training?

Some runners experiment with low-carbohydrate training sessions to encourage fat adaptation. While this may have some benefits, it should be used sparingly. Too much training in a low-glycogen state increases the risk of poor session quality and overtraining. Most of your runs should be well-fuelled to maximise performance and recovery.

How do I know how much carbohydrate I need?

Needs vary depending on your body size, training volume, and goals. Our new Carbohydrate Calculator helps estimate your optimal intake for training and racing, giving you a personalised starting point.

Why Carbohydrates Are Important for Training and Race Performance