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The Wilder Blog

What if every running shoe was size 10 – or every bike was a medium?

by Find Your Feet 18 Jan 2017

Article by Darryl Griffiths - Shotz Sports Nutrition 

Find Your Feet Blog

Imagine if all running shoes and bicycles came in one size and one shape. That was it, no other option but a size 10 shoe for running on the road, or a medium bicycle that didn’t allow you to adjust the seat height. Imagine if the running and bicycle companies treated us as if we were all exactly the same.

Sadly this is how the sports nutrition companies that make powdered and ready made drinks think of us. When you add a powdered sports drink to water you are making a preset solution, which we’re told will provide everything we need to supply the energy, electrolytes and hydration. They think we are all exactly the same and the conditions we train and compete in never changes.

Well we are different and the weather conditions are constantly changing and being locked in to a set volume of fluid, with a set amount of calories, with a set amount of electrolyte is akin to us all wearing the same size shoes and riding the same size bike.

There are around 6 - 8 different styles of running shoes in each size and different styles to suit men and women in an attempt to suit your specific needs. Bicycles come in a range of sizes, which can be customised to suit individual requirements. No one can tell you without proper assessment what will work best for you and it can be some time before you, through trail and error, find what works best.

Having performed over 1000 sweat tests on a range of athletes I can tell you, without hesitation, that you have a unique physiological makeup and you are not realising your true potential if you are relying on a powdered or ready made sports drink to provide everything you think you need. You can’t customise a powdered sports drink to suit your needs and you can’t adapt it to changing environmental conditions.

You are unique and you need to be able to customise and adapt your nutrition strategy to best suit you.

You are one of a kind and you do have specific needs when it comes to your sporting equipment and the same is true when planning a nutrition strategy to combat the negative effects exertion and fluid loss has on your performance. The amount of sweat you lose (sweat rate) is unique to you and this changes based on the level of exertion and the environmental conditions at the time. The concentration of sodium lost in that sweat is unique to you. As you experience different environmental conditions your sweat rate changes and so to does the accumulative amount of sodium you lose. You need to make changes accordingly so you’re not drinking an amount beyond what you need in cool conditions, but ensuring you are drinking enough in warmer conditions to minimise percentage of loss. More when it’s hot, less when it’s not. 

As for the amount of calories you require this is determined by the level of exertion, if you’re going faster than someone else it's likely you are expending a lot more energy and will require more calories than someone not going as fast. The amount of calories you can comfortably tolerate is determined by your unique digestive system and everyone’s is different. The amount of fluid, the concentration of sodium and the amount of calories that your stomach can process during activity is unique to you.

Through trial and error you have chosen your sporting equipment and customised it to suit your individual needs, or you are in the process of learning what works best for you so you can enjoy your chosen sport even more. The same needs to be done with the calories and fluid you choose to ensure you don’t experience stomach problems, at the same time avoiding early onset fatigue and the negative effects dehydration can have on your performance. Conversely the negative effects drinking too much in cold conditions can have on your performance.

I have written a book called Sweat. Think. Go Faster, which highlights what I have learnt working with athletes over the past 20 years. It’s pure applied research that isn’t taught at college or university, it’s information that will help you learn more about your unique qualities and how best to address them.

There are 7 billion people on the planet and no one is like you. 

So what are the unique qualities that set you apart from everyone else when it comes to choosing the right sports nutrition for you? When it comes to hydration and what suit your needs are the volume of sweat you lose and the sodium concentration of that sweat.

Here is an example of how wildly sweat rates can vary between individuals performing a one-hour indoor cycle. Twenty athletes were tested at the same intensity (3 watts per kilogram) in the same environmental conditions (27 degrees – 65% humidity). The lowest sweat rate recorded using pre and post weighing was 0.7 litres and the highest was 2.9 litres of sweat lost per hour. Fairly warm conditions saw a loss of 4 times the volume between the lowest and highest sweat rate. The average loss was 1.6 litres of sweat per hour. To show you how sweat rates change based on the environmental conditions here are the results of the same twenty athletes performing a one-hour indoor cycle at the same intensity (3 watts per kilogram) but this time at 12 degrees - 47% humidity. The lowest sweat rate recorded was 0.3 litres and the highest was 1.4 litres of sweat per hour. The average loss was 0.9 litres per hour. Quite a marked difference between sweat rates recorded in the cooler conditions compared with the warmer conditions even at the same intensity.

Interestingly, it’s where you sweat from that dictates the likely volume that you will lose, meaning if you sweat a lot from the head it feels like you are sweating a lot but the volume of sweat normally isn’t that high because it’s not a large surface area. Conversely, if you are a torso or leg sweater it may not feel like you are sweating a lot but generally the volume is higher due to the greater surface area. Some of you will start to sweat a lot in the first ten minutes and some of you won’t start sweating much at all for thirty minutes but at thirty one minutes it looks like someone has thrown a bucket of water on you. How much you sweat, where you sweat from and at what point you start to sweat is unique to you.

Another uniqueness when it comes to your sweat is the sodium concentration; some of you will lose more sodium in your sweat than others. Having performed over a thousand sweat tests, the lowest I have recorded is 311 mg and the highest is 2314 mg of sodium per one-litre of sweat. The sodium concentration of your sweat is an amount unique to you and it doesn’t change regardless of the intensity or weather conditions. What does change is the volume of sweat you lose, which is dictated by the level of exertion and the environmental conditions.

Your hydration strategy will constantly change. Here’s why you should never settle on a fixed volume of fluid.  

Using the sweat rates above let’s assume your sodium concentration of sweat is 1200 mg.  For every one-litre of sweat you lose, you lose 1200 mg of sodium. At 27 degrees – 65% humidity if your sweat rate was 0.7 litres per hour you would be losing 840 mg of sodium per hour (0.7 litres X 1200 mg = 840 mg). Conversely if your sweat rate was 2.9 litres per hour you would be losing 3480 mg of sodium per hour (2.9 litres X 1200 mg = 3480 mg). Even though both sodium concentrations are the same, the accumulative loss of sodium is wildly different due to the varying sweat rates.

Using the same sodium concentration let’s look at how the numbers change based on sweat rates in a cooler environment. At 12 degrees – 47% humidity if your sweat rate was 0.3 litres per hour you would be losing 360 mg of sodium per hour (0.3 litres X 1200 mg = 360 mg). Conversely if your sweat rate was 1.4 litres per hour you would be losing 1680 mg of sodium per hour (1.4 litres X 1200 mg = 1680 mg).

The examples show that while the concentration of sodium stays the same, the accumulative amount of sodium lost changes based on your sweat rate at the time. Knowing the sodium concentration of your sweat is one part, knowing your likely sweat rate in varying environmental conditions is the other part. With this knowledge you can plan a sound hydration strategy based on your specific needs in the environmental conditions and not lock yourself into a set volume of fluid.

For those of you who are active for long periods of time it’s likely you will encounter a range of temperatures and by using the examples above you can see how your hydration strategy (volume and concentration of fluid) will change during different times of the day as the environmental conditions change. This will require that you alter the volume of fluid that you consume so you don’t compromise your stomach by drinking too much in cooler conditions, but making sure you are drinking enough to minimise losses when it’s hotter.

Stomach complaints for those of you with low sweat rates are common especially in cooler conditions. You only need to drink a volume of fluid based on how much you are losing at the time. Drinking too much can have a similar effect on performance as not drinking enough in hotter conditions. It’s also very important to remember that the volume of sweat that you lose, regardless of the temperature, will always be more than the volume of fluid your stomach can process. For example if your sweat rate is only 0.5 litres (500 ml) per hour, it’s likely your stomach will only be able to tolerate 200 – 300 ml per hour. In hotter conditions if your sweat rate is 2.0 litres per hour the volume of fluid you are able to consume is governed by your stomach’s limitations and that might only be 1.2 litres per hour over an extended period of time.

Your stomach also has limits when it comes to the concentration of sodium it can tolerate. With the sodium example above of 3480 mg lost per hour, there will be a limit as to the amount of sodium the stomach can process per hour. As a guide you would aim to replace at least half of your losses, or more if your stomach was able to tolerate it. The key to a sound hydration strategy in the heat is to bridge the gap, as best you can, between how much fluid and sodium you are losing and how much your stomach can process/tolerate.


This takes us back to the very point of this article, a powdered or ready made sports drink is a one size fits all beverage that does not allow you to customise to suit your specific needs, nor does it allow you to adapt your hydration strategy to changing environmental conditions. How awesome would it be if we were all exactly the same? Pretty awesome for the sports drink manufacturers because all they have to do is make one product that suits everyone in all environmental conditions. 

Where to from here? Well that depends on how serious you are about your chosen sport or activity and if you are out there long enough that calorie expenditure and fluid loss impacts on your performance and/or health. Separating your calories from your hydration is the answer, meaning your hydration should not contain any calories, this way you can consume an amount of fluid that suits you and alter that volume of fluid based on the environmental conditions at the time. 

If you’re real keen on making sure you nail your hydration strategy, start to learn your likely losses when you are out training. It’s as simple as weighing yourself before and after a training session and the difference in pre and post weight is an approximation of how much sweat you have lost. If you’re a multi-hour endurance athlete it’s smart to do a sweat test during differing times of the day so you can see how your sweat rate changes based on the varying environmental conditions.

Do a sweat test with a friend or a group of friends to see how different sweat rates can be. Having this knowledge allows you to make a plan based on your own needs and the conditions at the time.

If you’re really keen you can get a test done that measures the sodium concentration of your sweat so then there is no guessing, you will have a set of numbers to work to. Rather than throwing a random amount of fluid down your throat you can avoid the many nutrition related issues that can plague athletes by just guessing what they need.

To learn more go to for the book, e-book, pdf file or sweat test kit.

For separating your calories from your hydration go to

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