A couple of weeks ago I was talking about which activities made you sweat the most (Swimming, cycling or running – which exercise is the thirstiest?), which all came from a question someone asked me a little while back – Do you sweat when you swim?

A very good question, and I’ve done more research so I can give you a really good and specific answer…

One of the great advantages to swimming is that when you’re done you’re soaking wet – which can make it look like you’ve worked out really hard. You might reek of unpleasant pool chemicals but at least you don’t have to worry about sweat. Right?

Well, actually, you do, yes!

As we know, sweating is the primary means for the body to cool down during exercise. The environmental temperature (in this case the temperature of the water) and how hard you work out both have a major impact on heat loss and therefore your sweat rate – and dehydration. But since you’re immersed in water and usually don’t notice that you’re sweating, you also may not realise you’re getting parched on the inside.

Put simply, hydration can present an extra challenge when you are exercising in the water because it decreases your ability to sense sweating and dehydration.

In most sporting conditions when the athletes are working hard, scientists tell us to expect sweat rates of 1-1.5 litres per hour. But these figures apply to athletes exercising on land. What about swimmers, surfers, water polo players, water aerobics devotees and lifesavers? As it is difficult to determine the amount you sweat because you’re already wet, the best way to assess how much fluid you lose during a training session is by weighing yourself pre and post training. According to the Sports Dietitians Association of Australia, for every 1 kilogram lost, 1.5 litres of fluid needs to be replaced.

So where does the sweat go? Into the environment. If you are on dry land, it will evaporate due to the cooling effects of the air or you’ll end up with salty sweat stains on your clothes. But since you are actually in water then it will end up, well, in the water. Which isn’t has horrible as it sounds because the volume of water you are perspiring is certainly minimal in relation to the body of water you are in.

Don’t let the sweat in the water put you off swimming in a pool full of sweaty people, however. Thankfully the pool is treated with chemicals to minimise problems associated with contamination. But remember that even though you are surrounded by water, you can still become dehydrated.

Bottom line: To prevent dehydration, drink water between laps and after you’ve finished training. If you’re performing high-intensity training, or swim for more than 60 minutes, keep hydrated throughout the day and consume sports drinks before and during the training session to replace the salts lost due to excessive sweating.

Kathleen Alleaume

Kathleen Alleaume is an accredited exercise physiologist and nutritionist and founder of The Right Balance