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Stay hydrated during sport

10/03/2016

Authors Matt Rabin and Robert Hicks explain the importance of replacing fluids when on a bike ride

Beginning training or competition with adequate hydration levels is paramount. Ensuring you have an optimised pre-hydration status will limit the risk of dehydration more efficiently than trying to hydrate while on the bike. What you’ve consumed over the last 24 hours will influence your hydration. Certain foods and fluids contain higher amounts of water than others, while some can promote fluid loss. Alcohol, for example, has diuretic properties that encourage the body to pass fluids.

Recommendations

  • Drink 500ml of water as soon as you wake up to replace the fluids your body lost overnight through respiration

  • Drink an additional 500ml of water two to three hours before you get on the bike. Drinking several hours before riding gives your body sufficient time to excrete any excess fluid that hasn’t been absorbed by the body

Although it sounds simplistic, passing urine is a reliable indicator of hydration status. It’s a good idea to check the colour of your urine. It should be a pale straw-like colour. Anything paler, and you may have taken on too much fluid; anything darker, and you haven’t taken on enough.

Drinking on the go

To avoid dehydration and hyponatremia, the two ends of the scale, current trends advise drinking at a rate that replaces the majority of sweat losses. But how do you know how much you’re sweating? Not an easy question to answer because there are so many factors that influence our sweat rates, from the outside temperature or your diet to the humidity in the air. Other factors such as your hydration status, fitness levels, body weight and clothing all play a role in how much you sweat.

Your hydration needs should be suited to you. Everyone is different and hydration is all about understanding how much you sweat and what is needed to cater to your specific needs. The content of sweat varies widely between people too. While all sweat contains salts, known as electrolytes, some cyclists naturally have more salty sweat than others. Electrolytes are a combination of essential salts, which aid muscle contraction and relaxation. They also help to keep the nervous and cardiac system functioning and they need replacing when they’re lost in sweat. There are four main electrolytes – sodium, chloride, potassium and magnesium – all with different jobs and roles to play, but it’s sodium that has the most important role, helping maintain the fluid balance of the body.

Sodium in sweat is measured in millimoles per litre (mmol/l), and concentrations can vary from anywhere between 15 to 93 mmol/l. To find out how much you sweat and the content of your sweat, you’ll need to undergo a laboratory test.

Applying the advice

Under 60 minutes: Hydration status is not a huge concern assuming you start in a hydrated state, unless you’re riding at high intensity and it’s hot outside.

Up to 90 minutes: Water is fine and effective at maintaining hydration levels, and drinking to thirst will be fine.

Over 90 minutes: It’s advisable to consume a sports drink with a carbohydrate content of 4–8% (4–8 g/100 ml). Known as ‘isotonic’ drinks, they contain a similar concentration of salt and sugar as the human body, so are absorbed by the body as quickly as water. These drinks cover all bases, providing hydration, fuel and electrolytes, all key to performance when you’re going hard on the bike.

In these longer rides, drinking to thirst isn’t always reliable as riding hard or eating while riding may stop you feeling thirsty. So when you set out on longer training rides, adopt a strategy, and aim to drink 120–180ml every 10–20 minutes. This will help replace most of your fluid losses while not overhydrating you. This roughly works out at one regular sized bidon an hour. Remember, if it’s hot outside (above 25?C) sweat rates can get as high as 2000ml per hour, meaning you’ll need to increase your fluid intake. Trying to drink two litres of fluid per hour to keep pace with fluid loss becomes difficult, uncomfortable and may be impractical, but you will need to increase your intake in hot conditions, so replacing 75% of fluid losses – three bidons per hour should prevent you from going above 2% dehydration. The more you become familiar with your weight before and after long rides, the more you can tailor your own individual fluid needs.

Make your own isotonic drink:

  • 500ml unsweetened fruit juice (orange, apple or pineapple work well)

  • 500ml water

  • ¼ teaspoon of salt

The Pain Free Cyclist: Conquer Injury and Find Your Cycling Nirvana by Matt Rabin and Robert Hicks is available for £11.89 from www.bloomsbury.com

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