How to plan your hydration

Hydration is key to both recovery and race performance, says Nigel Mitchell. Here's his failsafe hydration facts to counteract the effects of sweat loss…

As individuals we all lose fluid differently, so it’s useful to get to know your own fluid requirements

For us to really understand hydration there a few fundamental physiological points that people need to be aware of. Firstly, our bodies are made up of about 70% water, each cell working on a fine balance of fluid and salts (electrolytes, which are critical for maintaining the correct fluid balance), both inside and out. Even though we’ve evolved into a much more complex, ‘multi cell’ organism, our cells still depend on this delicate water/electrolyte balance to maintain homeostasis and function.


Fluid compartments

We can look at the body as a whole but to understand fluid better we need to break it down into compartments. In effect, we can split it into ‘intracellular’ and ‘extracellular’. This is a really simplistic view but it basically refers to the fluid inside each cell and the rest of the body’s fluid outside of them. This ‘extracellular’ fluid can again be sub-categorised, for example the plasma volume (the amount of fluid in the blood) and interstitial fluid (the fluid that surrounds the cell and mediates between blood, the cell and lymphatic system).

Sweat rates

So from an athletic perspective, why is hydration important? Well, most importantly, we’re constantly losing fluid as we sweat; the more we exercise the more we sweat, the sweat evaporating using heat energy from the body, which helps to keep us cool. But as we sweat there’s a pull of fluid, and if we don’t replace this we end up with a fluid deficit, which can lead to dehydration and ineffective thermal regulation. Mild dehydration usually results in a reduced blood plasma, so we see an increased heart rate for the effort we’re doing, while in severe dehydration cases, cells will actually die. 


As individuals we all lose fluid differently, so it’s useful to get to know your own fluid requirements. A simple way to do this is during a turbo session, working at about race-pace effort, in a room at a temp of 20°C. Weigh yourself (nude) and your drinks bottle before and after (this will account for fluid drunk), and the difference in weight will give you an estimate of your sweat rate per hour. You can make this more bespoke by trying to replicate the climate you’ll be racing in, heating up the room to the approximate temperature. This obviously doesn’t take account of humidity but it will at least provide a benchmark. 

These sessions can be done daily, and as the body adapts quickly you should start to notice a difference after just three sessions – an increase in sweat rate and a reduction in the concentration of the sweat.

Day-to-day hydration

Despite the climate in the UK, we’re not often sensible when it comes to hydrating and I’ve seen many athletes with chronic mild dehydration, which not only affects athletic performance but our work as well. For many of us, work itself provides a hydration challenge: we often work in an air-conditioned environment, which can increase the risk of dehydration. 

In cold weather, we tend to drink a lot less during training, but we still sweat and lose fluid. While we don’t need to take on as much fluid we still need to drink. One way to ensure this is to buy an insulated bottle and fill it with hot tea. The fact that the fluid is warm encourages you to drink. My favorite is a fruit or green tea, with some honey or agave nectar for some carbs and sweetness. If you’re not a good drinker, i.e. you go out for a 3hr ride and hardly touch your water, then again making the tea can really encourage you to drink.

Common sense fuelling

Like a lot of things, hydration is pretty simple if we follow a few common sense rules. For one, drink little and often and include some electolytes if doing long training and sweating a lot. There are plenty of hydro tabs on the market or electrolyte sports drinks, which, if used in moderation, can contribute positively to your overall fluid strategy. Foods can provide fluid as well, such as rice cakes (with actual cooked rice) and fruit and veg.

You’ve probably heard of hyponatremia but not drinking enough can actually be more dangerous. So follow my advice here and in the middle panel, and be sure to schedule in hydration ‘training’ before you hit the start line.


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