Nutrition

The 3 key nutrition moments

Before the race (48-72 h): Progressive carbohydrate loading. Increase the proportion of pasta, rice, bread and potatoes in your regular meals without gorging the night before. Your pre-race meal should be 3-4 hours before the start, high in carbs and low in fibre and fat to avoid stomach issues. Example: white bread with jam, a banana and coffee.

During the race: Your first gel or bar should go in at 30 minutes into the race, not when you already feel hungry. From there, every 30-45 minutes. If you wait until you bonk, it's too late: your body takes 15-20 minutes to absorb the carbohydrates. In ultras, alternate gels with solid food to avoid palate fatigue.

After the race (30-60 min): The recovery window is real. Take in 20-25 g of protein combined with 1 g/kg body weight of carbohydrates within the first hour. A recovery shake, a ham sandwich with banana or yoghurt with granola and fruit all work perfectly. Don't wait until you get home.

Product types: what to carry?

Energy gels: The most practical format during a race. They deliver 20-25 g of fast-absorbing carbohydrates in a small package. Ideal for high-intensity efforts. Hydrogel types (like Maurten) are better tolerated without water. Classic gels (GU, SiS) work just as well but are best washed down with a sip of water.

Energy bars: More satiating than a gel because they require chewing. They provide 30-45 g of carbohydrates and some include protein and fat. Ideal for long, low-intensity climbs in ultras, where the stomach tolerates solids better. Choose soft bars you can eat without stopping.

Isotonic drinks: Hydration + electrolytes + carbohydrates in one product. Ideal for carrying in soft flasks to complement gels. Look for formulas with sodium (>400 mg/L) and avoid those with too much sugar, which can cause discomfort.

Electrolyte salts: Capsules or effervescent tablets with sodium, potassium and magnesium. Essential in heat or high-sweat conditions. They don't replace food — they complement it. One capsule every 45-60 minutes in hot conditions is a common guideline, but every runner sweats differently: test in training.

Real food: Nuts, banana, dates, boiled potato with salt, cured ham, cheese, mini sandwiches. Common in ultras of 50 km or more, where spending 10+ hours on gels alone becomes unbearable. Aid stations at many Spanish races offer real food — but don't rely solely on them: carry your own backup plan.

How many carbohydrates per hour?

The amount of carbohydrates you need depends on the duration of the effort, not just the distance. These are reference ranges based on ISSN (International Society of Sports Nutrition) guidelines:

• Short trail (< 21 km): 30-40 g/h. One gel every 40-45 minutes is usually enough.
• Mountain marathon (42 km): 40-60 g/h. Two gels per hour or one gel + isotonic drink.
• Ultra 50-80 km: 60-80 g/h. Combine gels, bars and real food. Alternate between sweet and savoury flavours.
• Ultra 100 km+: 60-90 g/h. At these durations you need prior gut training to tolerate high intakes. Practise on long runs with the same nutrition you'll use on race day.

Important: carbohydrate intakes above 60 g/h require systematic gut training. Start with 40-50 g/h on your long runs and gradually increase over weeks. Your gut adapts, but it needs time.

Hydration: how much and what to drink

The general recommendation is 400-800 ml per hour, adjusting for temperature, humidity and your individual sweat rate. In heat (>25 °C) or on sun-exposed climbs, aim for the upper range. In cold or shade, the lower range is fine. Weigh yourself before and after a long training run to estimate how much fluid you lose.

Water or isotonic? If you're already taking gels and salt capsules, plain water works fine. If you prefer fewer products, an isotonic drink covers hydration + electrolytes + some energy in a single sip. Many runners carry one soft flask with water and another with isotonic. In races with frequent aid stations (every 8-12 km), you can carry less fluid.

The 4 most common mistakes

1. Testing new products on race day. The golden rule of sports nutrition: nothing new on race day. A gel that works for your training partner may wreck your stomach. Test every product in training before taking it to a race.

2. Starting to eat too late. Many runners wait until they feel hungry or bonk before taking their first gel. By then you're already in a deficit that's hard to recover from. Start at 30 minutes and maintain the cadence even if you feel fine.

3. Ignoring electrolytes in the heat. Drinking only water for hours dilutes blood sodium (hyponatraemia). In heat or high-sweat conditions, salts aren't optional — they're essential. If your urine is clear and you feel bloated, you're probably drinking too much and taking too few salts.

4. Not training your nutrition. Your long runs are the laboratory. Use them to test gels, bars, quantities and timing. Train your gut just like you train your legs. Runners who practise their nutrition plan in training have 30-40% fewer gastrointestinal problems on race day.