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Bite Size - Signs Of Dehydration, Causes & Treatment

The main reason for dehydration is insufficient fluid intake to match exercise sweat losses, says Dr Sam Oliver, exercise physiology lecturer at Bangor University. Case studies suggest that a two per cent drop in hydration may lead to a performance reduction of up to 30 per cent. hydration, one of the most common problems for athletes, is actually fairly easy to tackle.

Over the last few years, there have been conflicting opinions about how to address dehydration, with many experts suggesting that drinking to thirst adequately hydrates without risking the dangers of hyponatremia diluting the bodies sodium levels too much, which can be fatal. If you think about drinking while on the bike, take a swig.

Drinking more when sweating more is important, but so is replacing the electrolytes lost in sweat, so sports nutrition is a good choice, especially in hot and long sessions.

Triathletes and especially Ironman athletes can be more prone to dehydration due to not being able to take fluids on board during the swim section, so refueling on the bike should be a priority.

Dehydration symptoms

Dizziness while exercising


Dry mouth, lips and throat

Darkly coloured urine

Performance drop-off

How To Avoid Dehydration

Choose your drinks and supplements carefully. Don’t try out new brands or products on race day. Just drinking water may flush out minerals and salts so instead use electrolyte drinks as well as water for washing down gels.

Drink plenty the day before the race, topping up on electrolytes to avoid dehydration the next day. An extra bottle or two of electrolyte solution should do the trick.

Drink little and often during the race aim for every 10 minutes at the least, drinking to thirst in between and without swigging too much in one go, which can cause bloating.

Calculate your sweat-loss rate. Roughly speaking, weigh yourself before and after an hours exercise and take into account any fluid intake to measure how much you'll need.

This isnt exact as you lose more than just water while exercising, especially in long-course races, but it can help give an indication of where to start experimenting.

Medication and alcohol can affect your hydration levels. Avoid alcohol and excessive caffeine in race week. If you take antihistamines or blood pressure tablets speak to a doctor before racing in hot climates.

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