During the race
Fluid and carbohydrates by race duration
How we calculate
Your sweat. If you know how much you sweat per hour, we use your figure. If not, we estimate it as in our hydration calculator: 0.5, 0.9 or 1.3 litres per hour for a light, moderate or hard effort for a 70 kg person at 15-25 °C. We chose those values based on the published averages; in endurance sports, the average is around 1.3 litres per hour 5. We then adjust them for your weight and the forecast temperature, and keep them between 0.3 and 2.5 litres per hour 1.
How much to drink. To thirst and without exceeding 80% of what you sweat, up to a maximum of 0.8 litres per hour, as recommended by the German Nutrition Society (DGE) 1. In the triathlon, you do not drink during the swim: we only count the bike and the run.
Per aid station. From the distance and your time we work out your pace, and from that, how many minutes pass between one aid station and the next. On the bike, we give it to you in 500 ml bottles.
Sodium. 400 to 1,100 mg per litre of drink, and even more important if you sweat more than 1.2 litres per hour for more than 2 hours 1. To work out what you lose, we multiply your sweat by 920 mg of sodium per litre, in line with the average of about 900 mg reported by the DGE 1. If you get salt marks, we use 1,380 mg, a high value within the 175-1,512 mg per litre range given by the same source 1.
Carbohydrates. From 90 minutes onwards, 30-60 g per hour 1. Over 2.5 hours, up to 90 g per hour, combining glucose and fructose; at an easy pace, less, because you use fewer carbohydrates 3.
Before and after. Before, 5-10 ml per kilo of body weight in the 2-4 hours beforehand. After, 1.5 litres for every kilo you have lost 1. If, even drinking according to the plan, you would lose more than 2% of your body weight, we warn you: beyond that point, endurance performance suffers, especially in the heat 2.
The races
| Race | Distance | When | Average temperature for the month |
|---|---|---|---|
| Barcelona Marathon | 42.195 km on city streets | Mid-March | 7-16 °C |
| Barcelona Half Marathon | 21.1 km on city streets | Mid-February | 5-14 °C |
| Empúries Marathon | 42.195 km | April | 6-19 °C (Girona) |
| Ultra Pirineu | 100 km and 6,600 m of elevation gain | Early October | Varies greatly with altitude |
| Matagalls-Montserrat | 84 km on foot and 5,773 m of cumulative elevation change | September | 17-26 °C (Barcelona) |
| IRONMAN Calella | 3.8 km swim, 180 km bike and 42.2 km run | Early October | 14-22 °C |
| Bike ride around Girona | Example: 116 km and 1,300 m of climbing | All year round | Highs from 13 °C in January to 30 °C in July |
Sources: rules and official websites of each event; AEMET, Spain's state meteorological agency, 1981-2010 normals (average monthly lows and highs).
The data come from the rules and official websites of each event 8 9 10 11 12 13 and from the AEMET average temperatures for Barcelona and Girona 6 7. The bike ride is an example taken from the Turisme de Banyoles routes 14. Dates change every year: check them on your race's website.
Sodium per litre
How much sodium to have in your drink
How to use your plan
Try it out on your long sessions: the drink, the gels and the servings, at race pace and at similar times of day. That way you will know what suits you before race day 3.
For racing, mix each serving of Nitrus Isotonic (25 g) in 400-450 ml of water. That gives about 430-490 mg of sodium per litre, within the recommended range, with 15 g of carbohydrates, five electrolytes and all 13 vitamins. A 20-serving tub costs €19.90.
And remember that drinking too much is also a problem. In events lasting more than 4 hours, especially at an easy pace, drinking more than you sweat is the main cause of hyponatraemia: drink to thirst and do not finish heavier than when you started 4. To fine-tune your plan, see our sports hydration guide and the running nutrition guide.
Frequently asked questions
How much should you drink in a marathon?
Drink to thirst: between 400 and 800 ml per hour in most cases, without exceeding 80% of what you sweat. In cool weather and at an easy pace, less; in the heat, more. The planner gives you your own figure based on your weight, your time and the temperature.
Do you need to drink at every aid station?
No. Drinking at every one out of habit, especially in events lasting more than 4 hours and at an easy pace, is the main cause of hyponatraemia. Drink to thirst: with aid stations every 2.5 km, as at the Barcelona Marathon, a few sips at each one are enough.
How many carbohydrates should you take per hour in a race?
In events lasting 1.5 to 2.5 hours, 30-60 g per hour. In those lasting more than 2.5 hours, up to 90 g per hour, combining glucose and fructose and only if you have tried it in training. At a gentle pace, such as on a long-distance walk, less is enough.
How many servings of Nitrus do I need for a race?
It depends on how much you drink. For racing, mix each serving (25 g) in 400-450 ml of water: it provides about 195 mg of sodium and 15 g of carbohydrates. The planner tells you how many servings what you drink is equivalent to and whether one 20-serving tub is enough.
What if I know how much I sweat per hour?
Even better: enter your figure and the plan adapts to you. To find it out, weigh yourself before and after a long session at a temperature similar to race day and use our hydration calculator.
Sources
- Mosler S, Braun H, Carlsohn A, et al. Position of the working group sports nutrition of the German Nutrition Society (DGE): fluid replacement in sports. Dtsch Z Sportmed. 2020;71(7-9):178-184. View publication
- Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc. 2007;39(2):377-390. View publication
- Jeukendrup AE. A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Med. 2014;44(Suppl 1):S25-S33. View publication
- Hew-Butler T, Rosner MH, Fowkes-Godek S, et al. Statement of the 3rd International Exercise-Associated Hyponatremia Consensus Development Conference, Carlsbad, California, 2015. Br J Sports Med. 2015;49(22):1432-1446. View publication
- Barnes KA, Anderson ML, Stofan JR, et al. Normative data for sweating rate, sweat sodium concentration, and sweat sodium loss in athletes: an update and analysis by sport. J Sports Sci. 2019;37(20):2356-2366. View publication
- Agencia Estatal de Meteorología (AEMET). Valores climatológicos normales 1981-2010: Barcelona Aeropuerto. View publication
- Agencia Estatal de Meteorología (AEMET). Valores climatológicos normales 1981-2010: Girona Aeropuerto. View publication
- Zurich Marató Barcelona. Race rules. View publication
- Hyundai Mitja Marató Barcelona by Brooks. Race rules. View publication
- Empordà Turisme. Marató d'Empúries. View publication
- Salomon Ultra Pirineu. Ultra Pirineu 100K: route and aid stations. View publication
- Club Excursionista de Gràcia. Matagalls-Montserrat: rules and regulations. View publication
- Calella Barcelona Turisme. Ironman Barcelona Calella. View publication
- Turisme de Banyoles. Road cycling routes. View publication
A varied and balanced diet and a healthy lifestyle are important.