Thirsty? How dehydration could be affecting your workouts

Water glass

Our bodies are largely made up of water – around 60 per cent in fact – and even the slightest drop in this ratio can result in a significant decrease in performance.

While the human body can go for more than three weeks without food, you’d be pushed to get through a week without water

However, despite this fact, the percentage of British adults that forgo water is pretty staggering.  According to a 2018 study by the Royal National Lifeboat Institution (RNLI), 89 per cent of the population do not drink enough water to maintain healthy hydration levels. Slightly more worryingly, 20 per cent of men reported drinking no water at all during the day – compared with 13 per cent of women.

Water, it seems, is one of those areas of health and nutrition that people are willing to overlook, despite the importance of proper hydration.

According to ‘Sports Nutrition: An Introduction to Energy Production and Performance’ (Jeukendrup and Gleeson, 2010) “exercise performance is impaired when an individual is dehydrated by as little as 2 per cent of body weight”. What’s more, should you lose 5 per cent of your body weight to dehydration, your capacity for work diminishes by 30 per cent.  That’s a big deal if you’re looking for gains in the gym.

According to a 2018 study by the Royal National Lifeboat Institution (RNLI), 89 per cent of the population do not drink enough water to maintain healthy hydration levels

Moreover, dehydration doesn’t only affect endurance athletes, or those that pound away on the treadmill. If you arrive at the gym without properly hydrating beforehand, you could also be in for decreased performance. According to research by Sawka, Young, Cadarette, et al. (1985), the capacity to perform high-intensity exercise, which results in exhaustion within a few minutes, can be reduced by as much as 45 per cent should you lose just 2.5 per cent of your body weight to dehydration. Deadlifters take note!

It should be pretty obvious by now that hydration plays a central role in sports performance, and you may be sacrificing your progression if you don’t take it seriously.

However, it isn’t simply your performance that could be suffering from your hydration levels. Water plays a central role in many bodily functions, including: flushing out waste, healthy digestion, temperature regulation and helping to protect your tissues and joints by keeping them lubricated. There are also some studies that suggest that increased hydration could help with weight loss, by acting as a natural appetite suppressant and via an increase in lipolysis (the breakdown of fat in the body).

So, how much water should you be drinking?

We all know the standard Government recommendation of 6-8 cups of fluid per day, but what about when you’re exercising? According to Dieticians of Canada, depending on the sport or exercise, its intensity, and your individual rate of perspiration, “you could lose anywhere from 0.3 to 2.4 litres of sweat per hour”, which needs to be replaced.

They advise the following:

  • 4 hours before exercise – Drink 250 to 500 ml
  • 2 hours or less before exercise – Drink 125 to 375 ml
  • During exercise – Sip fluid during your activity. Avoid gaining weight, which can be a sign of over-hydration.
  • Immediately after exercise – If you drank regularly during your workout and there was no weight change, drink according to your thirst for the rest of the day. If you didn’t drink enough and lost weight, drink 500 to 750ml of fluid per 0.5 kg of weight you lost.

The advice is pretty simply: pay attention to your thirst. Water may not be the most exciting drink on the planet, but if it leads to optimal performance, both in the gym and in life, then there’s really no excuse to avoid it.

This blog was originally published in March 2019.

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