Hydration is a bit of a contensious subject when it comes to endurance sports. So how much should you drink?
I have heard different opinions from experts:
- drink when you are thirsty
- positive hydration strategy
Nigel Mitchel (team sky) was an advocate of the positive hydration strategy as part of Team Sky’s 2012 success. The idea being that you cant drink too much. On the other Rob Child (MTN Quebeka) says ‘drink when you are thirsty’.
As these are both top level nutritionists and sport scientists I dont have much too add to this discussion, on a scientific level
One thing to bear in mind is that this is very general advice, its important to bear in mind some of the risks regarding heat and hydration. This article has a good discussion on the subject http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1872071/ The take home message being you shouldnt attempt 100% fluid replacement over endurance events such as a 4hr marathon, particularly when you are sweating at your maximum
So how much should you drink?
Start with the common sense, drink enough so you dont get thirsty. However bear in mind that endurance racing pushes your body and mind to the limit which can change how thirsty you feel.
Use a hydration strategy
When I raced XC, I used a nutrition/hydration strategy. Events were relatively short (<2hrs), but temperature could be extreme. In 2013 i raced a National XC series race on the hottest day of the year, which included an exposed windless climb at <10mph with isolated temperatures hitting over 40 degrees celsiues.
My strategy in this race, was to feed 750ml bottles of water with electrolytes each lap (every 15mins), which i doused myself with each lap, and drank what i needed. I then used energy gel in addition to this.
In road racing, I generally use two nutrition strategies, one is for cold/wet weather then other for summer. In the summer I drink just water/electrolytes plus food/gels, in the cold/wet races i use a strong energy drink plus a bottle of water. The main challenge with road racing is the volume of liquid, when races last up to 4hrs in hot weather I may need over 2.5 litres of water, which is more than can be carried.
Adding salt or electrolytes is a sensible idea. I personally avoid electrolyte tabs, and opt for electrolyte powder
Simple hydration strategy for road races
- Work out the maximum you sweat in litres/hr, during a hard indoor training session
- Estimate the maximum duration of your road race
- Work out the total volume you could sweat in this time
- Try to make sure you have this volume of water/electrolytes available to you for the race.
- During the first hour, drink regularly.
- For the rest of the race continue to drink according to your judgement
The key thing with this strategy is that you have enough water available to you. In cold or wet races you may need to drink very little, so you might not want to have all that water avialble to you.
How much do you sweat?
When it come to hydration people are different, I typically retain a lot of water. In the past I have been away to a dry warm environment for a weeks training, then returned to wet cold conditons, after this i have put 4-5kg of body weight on in the space of a few days, this is body water which i am retaining due to adapting to sweating larger volumes.
Weigh yourself daily, particularly during periods of changing weather and exercise. Use the same weighing regime, i.e. after to going to the toilet in the morning and before eating or drinking. This will give you an idea of how much your water volume may change.
Work out how much you sweat in hard training.
The easiest way to do this is to work out your net weight loss during an indoor training session.
- use a training envioronment similar to the one you will race in, for the UK 20-22 degrees is about right.
- Use a powerful fan. This will mimic the air flow while you are cycling, to an extent.
- Weigh yourself without clothes/shoes before the session. Use the most accurate scales you can get your hands on.
- Do a hard 60min session
- Start with drink bottles full with a measured amount of water. Weigh any food you eat during the session.
- if you need to go to the toilet during the session weigh yourself before and after.
- Dry yourself after the session and wait a few minutes to allow your skin to dry.
- Weigh yourself without clothes.
- Work out the net fluid loss
I weighed 74.1kg at the start of the session, 73.7kg after the session and I drank 750g of fluid, I also lost 350g of fluid when going to the toilet. This means i sweated of 800ml of fluid during an hour.
Bear in mind there are all sorts of factors that will affect this result, the idea is just to give you an idea of how much fluid you use when training.