With the London Marathon fast approaching, lots of us are thinking about our hydration strategy in preparation for race day. We spoke to John Brewer, professor of Applied Sport Science at St Mary’s University Twickenham, and former head of sports science at Lucozade Sport, about the importance of a focused hydration strategy during a 26.2 mile race but also in the days before.
How much water one should consume 24 hours before a marathon very much varies from one person to another and also depends on weather conditions. I would strongly advise people to keep an eye on weather conditions. If it’s looking like it’s going to be hot and you happen to be running it in fancy dress, then you need to have a more focused hydration strategy.
You need to be thinking about your hydration and nutrition strategy in the days before the marathon, not just the day before or the morning of. It’s a little bit like watering a garden – if you water it just before the flower show, it’s going to be too late.
In lots of city marathons, people often travel the day before and get caught up in all of action, such as the London Marathon Expo, so it’s easy to forget to hydrate. Make sure you carry a bottle of water with you and also an energy top up. Keep some snacks in your pocket if you’re out, like jelly babies, wine gums and bananas to make sure you stay topped up.
Topping up stores is crucial. Something like an isotonic drink is the perfect way of giving you that final boost of energy, fluid and fuel. I would recommend taking a bottle of water with you from your home or hotel to the start line to sip on. As long as your urine is a clear straw-like colour, you’re in a good state.
If you’re urinating every five minutes, you’ve probably over done it and that’s the time to back off. It’s a bit like running a bath: once the bath is full to the brim, you might as well turn the bath off because the water is just going to go in and out the other side.
You need to do the urine colour check. It’s important your urine is a clear straw-like colour. As long as you’ve got into that state the day before the marathon then actually you can relax.
Once the gun goes, the best guideline is small amounts, relatively frequently. It is common for runners to overdo it. Using the London Marathon as an example, if you drank a full bottle of everything offered on the course (I think it’s in the region of eight to nine litres per person), it’s gong to be way too much.
If you’re running London, I would strongly advise using the isotonic drinks at the various Lucozade Sports Stations dotted around the course at five, 10, 15, 19 and 23 miles. They’ll give a combination of good fluid, fuel and electrolytes. It’s almost important to make use of the water stations.
The guideline I normally give at the London Marathon Expo to the marathon runners is to drink about half to a third of each bottle. Each bottle of isotonic drink contains about a mile’s worth of energy.
Depending on conditions, sweat rates of two to three litres an hour are not uncommon in marathon running. I would recommend consuming between two and four litres of water as a general guideline but it depends on weather conditions and obviously if you’re in fancy dress!