Thursday, 20 November 2014

How's your hydration?

I've recently had a couple of instances where I've realised that I probably haven't been drinking enough water when I've been exercising.  I think this is particularly because I've started doing more strength training, rather than cardio, which have different exertion levels.  But with summer coming, I know I need to make it a bit more of a priority.

I'm actually pretty bad in general when it comes to regular water intake.  I've tried to make it a habit, but none of the normal tricks seem to work - having a glass of water by my computer, having a post-it reminding me to drink, having an app on my phone giving me regular reminders to drink water.  I just don't.

So although I've accepted this particular flaw, I still want to know the best way to ensure that I'm sufficiently hydrated for my exercise.  I've done a little research that I thought I would share with you.

Why should I drink water?

We all know we should drink water.  But sometimes we need to be reminded of why water is so important to our bodies.  Here are some of the reasons.

In terms of what your body is made up of chemically, water is number one.  It makes up about 60 percent of your body weight. Every system in your body depends on water. For example, water flushes toxins out of vital organs, carries nutrients to your cells, and provides a moist environment for ear, nose and throat tissues.  Basically, if you are even slightly dehydrated, you are preventing every system in your body from working effectively.

Although you are probably dehydrated at some level during much of the day, untreated dehydration can lead to life-threatening complications such as:

  • heat exhaustion
  • heat cramps
  • heatstroke
  • seizures (due to electrolyte loss)
  • low blood volume
  • kidney failure
  • coma

What are the signs I'm not drinking enough water?

There is an old addage that by the time you feel thirsty, you are already dehydrated.  I found a list of dehydration symptoms ranging from mild symptoms, to severe symptoms considered to be medical emergencies requiring immediate medical attention (avoid! avoid!):

Symptoms of mild to moderate dehydration include:
  • sleepiness
  • dry mouth
  • increased thirst
  • decreased urination
  • less tear production
  • dry skin
  • constipation
  • dizziness
  • lightheadedness
  • headache
  • constipation

Severe dehydration is likely to cause the following:
  • excessive thirst
  • lack of sweat production
  • low blood pressure
  • rapid heart rate
  • rapid breathing
  • fever
  • sunken eyes
  • shriveled skin
  • dark urine

When it comes to dehydration and exercise performance, the Australian Institute of Sport (AIS) suggests that dehydration impairs performance by causing the following:
  • increased heart rate
  • impaired heat regulation
  • increased perceived exertion (i.e. exercise feels harder than usual and the athlete fatigues earlier)
  • reduced mental function
  • reduced skill level
  • stomach upset

All levels of dehydration impair performance and the magnitude increases as the degree of dehydration increases.

Here's a neat little table I found:


How much water do you need generally?

The general advice you see is that you should drink eight to ten glasses per day for an average, non-active person. Individuals on the go, athletes, and people exposed to high temperatures should increase their water intake to avoid dehydration.

It is also recognised that required water intake is individual - some people need more water than others, depending on factors such as their normal sweat levels, exercise, and the climate of where they live.  When we went to Thailand the humidity meant that I drank significantly more water than usual!

Remember also that when you're sick your body may be losing more water than normal that you need to replace - especially when you have a fever, diarrhea or vomiting.

How much water do you need when you exercise?


Although we can see that we just need water to help our body function effectively, this is compounded when we throw exercise into the mix.  Why? Because when we exercise, our body uses sweat to regulate our body temperature.  When we sweat, we lose not only water, but also essential minerals, which, if not replaced can have additional side effects.

There are three stages of exercise that you need to think about your fluid intakes:

  1. Pre-exercise - generally you should drink 1-2 cups of water prior to exercising.  This may be increased if you are going to be exercising with high intensity or for a long period of time, or it has been a while since you last had some water (ie. you exercise as soon as you get up in the morning). 
  2. During exercise - basically you should drink enough to replace the fluids you are losing (see below for some info on how you can estimate your fluid loss).  In generally, drinking about 2 cups for every hour of low intensity exercise, and increase that if you increase your intensity.
  3. After exercise - keep hydrating!  You may not feel thirsty, but by having at least 2 cups of fuid after your workout should go a long way to replacing the fluids you have lost.

How can I estimate how much water I should be drinking during exercise?

The AIS suggests weighing yourself before and after exercise is a good way to understand how much fluid you lose during exercise.  Each kilogram of weight loss indicates one litre of fluid loss.  For example, if you have lost 500g after a workout session, you have sweated out about 500mls or two cups of fluid that you didn't replace during exercise.  If you know that you drank about one litre, or 4 cups of water during your workout, then you actually sweated out about 1.5 litres during exercise.

In order to minimise dehydration, you need to drink enough during exercise to match their sweat losses.

When is water not enough?

If you are exercising for less than an hour, drinking just water is probably going to be enough.  But if you exercise for longer, or at a very high intensity, you also need to replace the minerals you lose through sweat to ensure you can keep performing optimally.

 If your activity lasts an hour or more, a fluid that contains carbohydrates, minerals and electrolytes (like sodium, potassium and magnesium) may include:

  • fruit juice (probably diluted with water)
  • sports drinks like Gatorade and Powerade
  • Coconut water
  • you can add salt tablets to water if you are concerned about your sodium loss


What is your liquid intake of choice for working out?  Does it change depending on the type of exercise you're doing?

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