In 30 seconds
- IRONMAN Calella-Barcelona is usually held in early October: a 3.8 km swim, 180.2 km on the bike along the Maresme coast and a 42.2 km run.
- In the heat, sweating 1-1.5 litres per hour is common. The benchmark is a drink with 0.5-0.7 g of sodium per litre and up to about 90 g of carbohydrate per hour in a race this long.
- In an Ironman averaging 23 °C, 10 well-trained triathletes lost 3% of their body weight with no signs of thermoregulatory failure: you do not need to replace all your sweat.
- Drinking too much is also a risk: in Ironman-distance triathlons, asymptomatic hyponatraemia has been found in up to 25% of participants.
In a triathlon in the heat, start drinking at the beginning of the bike leg, with a plan based on your sweat: a drink with 0.5-0.7 g of sodium per litre and up to about 90 g of carbohydrate per hour, without gaining weight. At IRONMAN Calella-Barcelona, that means arriving well hydrated at the start, using the bike to drink and eat, and keeping cool on the run.
We are a Girona company, and this is a home race for us. Here is what the consensus statements on exercise in the heat say, and how to apply them on the Maresme coast.
IRONMAN Calella-Barcelona in numbers
You will also see it called IRONMAN Barcelona, but the start and finish are in Calella. It is usually held in early October: the 2026 edition was scheduled for Sunday 4 October, starting at 8 am 1.
| Leg | Distance | Course | What it means for your hydration |
|---|---|---|---|
| Swim | 3.8 km | One lap in the Mediterranean, starting and finishing on Calella beach | You cannot drink: arrive well hydrated |
| Bike | 180.2 km | Two laps along the coast, between Calella and Montgat | The longest leg, with bottles and food on board |
| Run | 42.2 km | Three laps between Calella and Santa Susanna, through Pineda de Mar | Sips at the aid stations, and keeping cool |
2026 course, according to the Calella tourism website. Check the athlete guide every year.
In early October, the Barcelona coast is still warm and humid. At the Barcelona airport station of AEMET, Spain's state weather agency, the average October maximum is 22.1 °C, the minimum 13.5 °C and relative humidity 73% (1981-2010) 3. We explain why humidity makes the heat harder to handle in training in heat and humidity.
The weather can change, though. The 2026 edition was called off the day before: Civil Protection activated the emergency phase of its flood plan because exceptional rainfall was forecast 2. Prepare your plan for the heat, and check the forecast in the days before.
Long-distance triathlon in the heat
Three numbers to understand your hydration in an Ironman
Why the heat matters so much in a long triathlon
In the heat, sweating 1-1.5 litres per hour during hard efforts is common, and some people exceed 2.5 litres 4. In warm conditions, losing more than 2% of your body weight in water usually starts to hold back performance, and dehydration increases the strain on your heart and your heat load 4.
That said, you do not need to replace all your sweat in an Ironman. In a study of 10 well-trained triathletes, in a race averaging 23 °C and 60% humidity, they lost an average of 3% of their body weight and finished with a core temperature of 38.1 °C, with no signs of thermoregulatory failure 5.
The heat consensus adds a nuance. In events such as an Ironman, where significant dehydration is expected, drinking only to thirst may fall short 4. That is why it pays to arrive with a plan based on your own sweat: you can work it out in 3 steps with how to calculate your sweat rate. The general framework is in the sports hydration guide.
Before the start
- In the days before. To arrive well hydrated at an event in the heat, the consensus suggests drinking 6 ml per kilo of body weight every 2-3 hours 4.
- On race morning. Drink 5-10 ml per kilo of body weight in the 2-4 hours beforehand: 350-700 ml if you weigh 70 kg 8. Pale yellow urine shows you are on track 8.
- If it is hot. According to the consensus, an ice slushy, about 1 litre of crushed ice at 4 °C or colder, taken before or during exercise, can cool you down more than cold water 4.
- If summer is long gone, or you live somewhere cooler. Acclimatisation takes 1-2 weeks of sessions of at least 60 minutes in the heat 4. We go into detail in exercising in hot weather.
Carbohydrate on the bike
Where 90 g of carbohydrate per hour comes from
On the bike: where you drink and eat
You cannot drink while you swim. The bike is the longest leg and the one where you can carry bottles and food: it is your chance to catch up.
- Carbohydrate. In ultra-endurance events, the benchmark is about 90 g per hour, from a mix of sources such as glucose and fructose, so that your body can use it all 7. The heat consensus suggests 30-60 g per hour once you pass the first hour of exercise, and up to 90 g if you go beyond 2.5 hours 4.
- Sodium. A drink with 0.5-0.7 g of sodium per litre 4. The German Nutrition Society widens the range to 400-1,100 mg per litre 8.
- Fluid. Drink regularly, without replacing more than 80% of what you sweat 8. As a guide, 0.4-0.8 litres per hour is well tolerated during hard efforts 8.
Do a dress rehearsal on your long rides. Weigh yourself before and after, and use the hydration calculator to work out how much you sweat. If you are racing IRONMAN Calella, you will find the race already loaded in the race hydration planner. If you finish weighing the same as at the start, or more, you have drunk too much 6. For the rest of your fuelling on the bike, see the cycling nutrition guide.
| When | What to do |
|---|---|
| 2-4 hours before | Drink 5-10 ml per kilo of body weight: 350-700 ml if you weigh 70 kg. Pale yellow urine shows you are on track. |
| Swim | You cannot drink. If it is hot, an ice slushy before the start helps you cool down. |
| Bike | Drink regularly, without going over 80% of what you sweat. A drink with 0.5-0.7 g of sodium per litre and up to about 90 g of carbohydrate per hour. |
| Run | Sips at every aid station, without gaining weight. Cool down with ice. |
| After the finish | About 1.5 litres for every kilo of body weight lost. |
Sources: Mosler et al., 2020; Racinais et al., 2015; Jeukendrup, 2014; Hew-Butler et al., 2015.
On the run: keep cool and do not overdo it
By the time you start the marathon, you have been racing for hours. Keep taking sips at the aid stations, with the same approach as on the bike, and use them to cool down: the consensus includes crushed ice and iced towels to bring your temperature down 4.
Drinking too much is a risk as well. In Ironman-distance triathlons, asymptomatic hyponatraemia has been found in up to 25% of the participants tested 6. The main risk factor is drinking more than you sweat over a sustained period, and almost all cases with symptoms have occurred in people who maintained or gained weight 6.
Taking more salt does not prevent it if you drink too much 6. If you have a headache, nausea, vomiting or confusion, go to the medical tent. We explain more in drinking too much water during exercise.
After the finish
To replace lost fluid, the benchmark is about 1.5 litres for every kilo of body weight lost 8. If you have lost 2 kg, that is about 3 litres, in small sips over the following hours 8.
Sodium helps you hold on to what you drink: a drink with sodium, a broth or soup, and a meal 8. You will find the details in how to rehydrate after training.
How to use Nitrus Isotonic
Each 25 g scoop of Nitrus Isotonic in 400-500 ml of water provides about 195 mg of sodium, 148 mg of potassium, 15 g of carbohydrate and all 13 vitamins, with no caffeine. Depending on how much water you use:
| Preparation | Sodium per serving | Sodium per litre | Carbohydrates per serving | Carbohydrates per litre |
|---|---|---|---|---|
| 25 g in 400 ml | 195 mg | 488 mg | 15.1 g | 37.8 g |
| 25 g in 500 ml | 195 mg | 390 mg | 15.1 g | 30.3 g |
Each 25 g serving contains 0.488 g of salt (about 195 mg of sodium), 148 mg of potassium and 15.13 g of carbohydrates.
In the heat, mix it with 400 ml: that gives 488 mg of sodium per litre, within the German Nutrition Society's range and very close to the heat consensus benchmark 8 4. If your sweat is very salty, add sodium from other sources.
On the bike, one bottle of Nitrus an hour gives you 15 g of carbohydrate. To reach 60-90 g, you will need to add gels, bars or another drink. If you are unsure how many bottles you need, read how much isotonic drink to have per hour.
Riboflavin (vitamin B2), vitamins B6, B12 and C, niacin, pantothenic acid and folate contribute to the reduction of tiredness and fatigue. A varied and balanced diet and a healthy lifestyle are important. We are a Girona company, and we deliver in 1-2 working days to mainland Spain and in 24-72 h to mainland Portugal.
Frequently asked questions
How much should you drink in an Ironman in the heat?
It depends on your sweat: in the heat, sweating 1-1.5 litres per hour is common. Drink regularly, without replacing more than 80% of what you sweat, and weigh yourself on long training sessions to learn your own numbers. Losing up to 3% of your body weight is common in an Ironman.
How much sodium do I need in a triathlon?
The benchmark from the consensus on exercise in the heat is a drink with 0.5-0.7 g of sodium per litre. If your sweat is very salty, you may need more from other sources, such as gels or sodium capsules.
How many carbs per hour in an Ironman?
In ultra-endurance events, the benchmark is about 90 g per hour, mixing sources such as glucose and fructose. Try it out on your long training sessions before race day.
When is IRONMAN Calella-Barcelona?
It is usually held in early October in Calella, on the Maresme coast. The 2026 edition was scheduled for Sunday 4 October and was called off the day before because of a warning of exceptional rainfall. You will find the date of the next edition on the official IRONMAN website.
Can you drink too much in an Ironman?
Yes. In Ironman-distance triathlons, asymptomatic hyponatraemia has been found in up to 25% of participants. The main factor is drinking more than you sweat: if you finish weighing the same as at the start, or more, you have drunk too much.
Sources
- Calella Barcelona (Calella tourist board). Ironman Calella-Barcelona: date, swim, bike and run for the 2026 edition. View publication
- TRI247. IRONMAN Barcelona cancelled on eve of race as severe weather threatens region. October 2026. View publication
- Agencia Estatal de Meteorología (AEMET). Valores climatológicos normales 1981-2010: Barcelona Aeropuerto. View publication
- Racinais S, Alonso JM, Coutts AJ, et al. Consensus recommendations on training and competing in the heat. Br J Sports Med. 2015;49(18):1164-1173. View publication
- Laursen PB, Suriano R, Quod MJ, et al. Core temperature and hydration status during an Ironman triathlon. Br J Sports Med. 2006;40(4):320-325. 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
- Jeukendrup AE. A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Med. 2014;44(Suppl 1):S25-S33. View publication
- 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
Information based on published studies. It does not replace the advice of a doctor or registered dietitian. The results describe what was measured in each study, not the properties of any specific product.
