Ask RIDE…How much should I drink on hot days?

Good morning RIDE team,

I am one of those riders who sweats a lot on hot days. During long summer rides my jersey will be caked in white salt while some of my friends jerseys look fine. Does this mean I am drinking the wrong fluids or not enough? What can I do to make sure this type of thing is not detrimental to my performance?

Hi Richard,

There can be significant differences between an individual’s rate of sweat and electrolyte (salt) loss while exercising in similar conditions. Sweat rates of 1.2-2.5 litres per hour is normal among men in hot and humid conditions. The two main electrolytes lost in sweat are sodium (Na) and chloride (Cl) and the sodium concentration of one litre of sweat can range from 800 to 3600 mg depending on the conditions.

So why can one rider have a greater electrolyte loss than another?

Environment: Riders who have trained for less than two weeks in a hot or humid environment will tend to lose more electrolytes than those who are conditioned to that particular environment.

Fitness level: Well trained riders tend to lose fewer electrolytes in their sweat than those who are not well trained.

Diet: Individuals with a high salt diet will tend to lose more sodium in their sweat that those on a lower salt diet.

Genetics: Some athletes have  naturally active sweat glands, meaning they lose more fluids and electrolytes.

So to answer your question on whether you are drinking the wrong fluids or not enough you must asses your rate of fluid loss. This can be done at home by taking your dry weight measurement before and after a one hour ride under the range of conditions that you would generally encounter during training or racing. Once you have established your sweat rate it is important to adopt a hydration strategy to match your needs.

It is important to note that fluids can be lost at a faster rate than you can rehydrate, as most people can only effectively reabsorb about between 800-1000ml an hour. Drinking to little or too much can be detrimental, so establishing your own rate of fluid intake is very important. On those days when you are going to finish slightly dehydrated then follow a post training or event rehydration strategy to match your requirements.

On shorter rides of 1-2hrs you may be able to get away with drinking water but on longer rides and events you will best served by taking your fluid replacement with an added electrolyte.

Ideally the electrolyte needs to best replicate the ratio of salts that you are losing and in similar quantities. Most well formulated products should do this and some will also have the facility for you to further customise them for your specific needs.

Even a fluid loss as low as 1-2% of total body weight affects temperature regulation and reduces endurance capacity and aerobic performance. Higher levels of dehydration impair mental concentration, alertness, muscular strength and endurance, physical work capacity, and increases the risk for heat injury.

Maintaining proper fluid and electrolyte levels is critical to performance.

Hope this helps,


Toby Cogley is an endurance athlete with over 20 years of training and competition experience.

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