London Marathon?… It’s going to be HOT HOT HOT…

London Marathon?… It’s going to be HOT HOT HOT…

Race Preparation

Bl**dy Typical! You’ve trained all winter like you’ve been living in Scandinavia, you’ve completed more snow runs than a polar bear chasing a BBC film crew and now less than one week before the big event, it’s going to be hotter than the Costa del Sol! Weather (see what we did there!) you love it or not the Great British weather is as unpredictable as… well the Great British weather!

Remember this. Your training is done. You are ready. So the next thing you can do is “control the controllables” as we say at the SHED.

It’s going to be hot so you need to be prepared.

Hydrating for the event.

Drink, drink, drink and drink some more! Whether it’s cold or hot keeping yourself topped up with fluid is essential. Water is a macronutrient and makes ups 50-60% of your body weight, it aids many of the body’s processes including sweating where it stabilises body temperature, blood plasma volume which helps to transport nutrients to the exercising muscles and waste products such as lactic acid and carbon dioxide away.

There is very little danger associated with drinking too much fluid. The kidneys of a healthy adult can process 15 litres of water a day. Drinking too much water, or water intoxication as it is known is extremely unlikely even if you drink a lot of water at once. One commonly referred to condition known as hypernatremia, a dilution of blood sodium, can lead to dizziness, mental confusion and in severe cases more serious conditions such as seizures, respiratory failure, and even death. This is due to an imbalance of electrolytes, however, this can easily be remedied and complete recovery can be expected within a few days. If you follow a good race hydration strategy the chances of this occurring are very rare indeed.

Drinking before the race

A study of 5K and 10K runners showed performance in both distances dropped by as much as 6-7% when slightly dehydrated by 2% of their bodyweight. Fluid intake before a race has been shown to keep heart rate and body temperature lower than that of runners who do not hydrate properly. Good hydration creates less strain on the body and maintains a good mental state as it reduces the perception of exertion. Drinking excessively or hyperhydration, however, is not possible before an event and if you drink large volumes you will end up with countless bathroom breaks which can then increase anxiety before a race!

Pre-Race Fluid Strategy

Your objective should be to ensure you are well hydrated before you run so keep your water bottle close at all times. Drinking 500ml two hours before your race is generally a good way to ensure you are well hydrated. If you do not feel the need to urinate within the first hour then you can top up further with an additional 250ml of fluid. Try not to consume additional fluid after this leading up to the race start. Any excess fluid that is not needed by the body will take between 60-90 minutes to eliminate. As you near the race start try to consume a further 200-250ml , 5 to 15 minutes before.

Race Fluid Strategy

Feeling thirsty is a brain mechanism telling you that you are dehydrated and that you must drink immediately. Fluid balance is essential to running performance and if you wait to feel thirsty it is already too late and you are affecting your running performance. Drinking on a run lasting less than 30-minutes, however, is not necessary as it has little effect on performance. Fluid needs vary between runners of different shapes, sizes and ability as well as being determined by the amount you sweat. The average sweat rate during running is around 1 liter per hour of running at a steady rate. The aim is to maintain this fluid weight whilst you run as any unnecessary loss will decrease you performance. You should therefore aim to top-up your fluids every 15-20 minutes in hot weather or race events by consuming around 120 – 240ml depending on your sweat rate and pace. Be sure to experiment with your fluid intake during training so you get a feel for how your body responds in different weather conditions.

If you are already well hydrated and drink additional unnecessary fluid you will get whats known as ‘jelly belly’. This feels like you have a washing machine in your stomach as you can feel water sloshing about as you run which can be uncomfortable.

Water loss

Water Intake

60% Urine

5% Fecal Loss

15% Skin Evaporation

15% Hummidified during Respiration

5% Normal Sweating

60% drinking fluid

30% Water in foods

10% Cell metabolism


Before Race

Race Start

Post Race

500ml before

250ml 1 hour before

200-250ml 5-15min before

120-240ml every 15-20minutes Hot weather (Fast Pace)

or 35-45minutes (Easy Pace)

60mins (Cool weather)

1 litre for every kg of weight lost

You may need to drink more or
less than this depending on your
pace and sweat rate. Let’s face
it though you’re probably going to have a beer anyway! 🙂