Hydration before, during and after a race

Before

Drink normally in the days before, no last-minute chugging

During

In most races, drink to thirst

Aid stations

Use them calmly and test in training what you will take

Watch out

Drinking too much is a risk too

After

Rehydrate gradually, with water and food

Your case

Ask a doctor or a registered dietitian

Being well hydrated on the start line is not something you fix on race morning; it comes from drinking normally in the days before. There is no need to force water down: if you drink as usual, eat a varied diet and your urine is a pale colour, you are on the right track.

The classic mistake is the opposite of what people fear: downing bottle after bottle just before the start in case you run short. All it does is fill your stomach and send you looking for a toilet in the start pen, with no benefit at all.

The most useful thing is to repeat the routine you already know from your long training sessions: the same breakfast, the same drink and a few sips before the start if you feel like it.

For most runners in most races, thirst is a good guide. If you are thirsty, drink; if you are not, there is no need to force yourself every kilometre. It is a simple way to avoid both drinking too little and drinking too much.

In short events, such as a local fun run or a DEKA MILE, many people do not need to drink anything while racing. Longer events are a different story, and there it pays to have practised what and how you drink beforehand.

Aid stations are there to help you, not to make you stop at every one. Check the race guide beforehand to see where they are and what they offer (water, sports drink, fruit…), so you know what to expect and nothing catches you off guard.

When you reach one, do not dive at the first table: there are usually more cups a few metres further on. Grab a cup, pinch the rim so it does not spill and sip while you walk a few steps. Dropping cups where the organisers ask you to is part of the race too.

• Check which drink will be served and try the same or a similar one in training.
• If you carry your own drink or gels, stick to ones you already know.
• A sip when you are thirsty beats half a cup out of obligation.

For years the advice was to drink as much as possible. We now know that drinking far more than you lose can dilute the salt in your blood, a condition that in serious cases is called hyponatraemia and needs medical attention. It is uncommon, but it mostly happens during long efforts and to people who keep drinking without being thirsty.

Signs such as swollen hands or belly, nausea, headache or feeling confused should never be ignored, whatever the cause. If you notice them, stop and tell the race medical staff.

When you sweat you lose not only water but some salt as well. Everyone sweats differently: some finish with white salt marks on their kit, others barely sweat at all. That is why no single amount works for everybody.

In the heat you sweat more and feel thirsty sooner, so pay closer attention: make use of the aid stations, cool down by pouring water over yourself if the organisers allow it and adjust your pace. In long efforts, such as a trail race, a marathon or an obstacle race lasting many hours, many athletes use drinks with salts or electrolytes.

If you plan to do so, try it during your long training sessions and, if you are unsure what suits you, ask a professional well before the race, not on the day.

Once you cross the finish line, drink at an easy pace and have something to eat with it. Food also provides water and salt, and helps your body replace what it lost without having to gulp everything down at once.

Keep the habit for the rest of the day: drink when you are thirsty and check that your urine returns to its usual pale colour. If you are racing again the next day, the afternoon before is part of your preparation.

Pulse is not a medical or nutrition service. This article is general information for healthy runners and does not replace an assessment by a professional.

If you have a medical condition (heart, kidney, diabetes, blood pressure…), take any medication or are facing a very long or very hot event, see your doctor or a registered dietitian to find out how you should hydrate in your case.

• Do I have to drink at every aid station?

  Not necessarily. In most races, drinking when you are thirsty is enough. Aid stations are there so you can, but you do not have to stop at every one, especially over short distances or in mild temperatures.

• Is it bad to drink a lot of water right before the start?

  Forcing down lots of water just before the start gives you no advantage: it fills your stomach and sends you to the toilet. It is better to arrive hydrated by drinking normally in the days before and to take only a few sips beforehand.

• Do I need drinks with salts or electrolytes?

  In short races, usually not. In long efforts or in strong heat, many athletes use them. It depends on the person and the event, so try them in training and, if you are unsure, ask a professional.

• How do I know I have rehydrated after the race?

  A simple reference is that your thirst goes away and your urine is a pale colour again. Drink calmly, eat something and do not try to make up for everything at once. If you feel unwell, go to the medical staff.

• Can Pulse tell me how much I should drink?

  No. Pulse is not a medical or nutrition service, and this article is general information only. To find out how to hydrate in your case, especially if you have a medical condition, take medication or are doing a very long event, consult a doctor or a registered dietitian.