Question 1

As an athlete, why is it important to have your sweat tested?"

Accepted Answer

It is important to have your sweat tested to determine the amount of sodium you lose in your sweat – and sodium is key to performing at your best by, amongst many other things, avoiding cramp and reducing fatigue (explained further below in this section). Each individual will lose a different amount of sodium in their sweat, this can range from 200mg/l to 2000mg/l, and that needs to be replaced. This amount is genetically determined so a “one size fits all” approach just won’t cut it. By having your sweat tested, we can establish your sodium loss number, then by combining this with your sweat rate we can personalise your hydration plan to have you performing at your best.

Question 2

Why is sodium so important to performance?

Accepted Answer

In short, the main reasons sodium (Na for short) is so important for performance are; Maintaining fluid balance in the body Absorption of nutrients in the gut Maintaining cognitive function Nerve impulse transmission Muscle contraction Avoiding cramp Diving into these important factors further; Maintaining fluid balance in the body Intuitively it makes sense that we want to have fluid balance across the body, but why is that important, particularly when exercising? Our body is made up of 50-70% water (we’re basically just a big water balloon), around a third of that fluid is extracellular fluid, a.k.a ECF (i.e. outside of your cells). Blood is a perfect example of this. Most of your body’s sodium is in this ECF which makes it super salty! Diving back into your year 7 biology, fluid balance is maintained through something called osmosis, basically where there is a higher concentration of salt, more fluid will be retained, so more sodium = more fluid and less sodium = less fluid. So to stay hydrated you need to maintain your sodium levels! When we exercise, our body sweats to maintain a safe internal temperature, this sweat is drawn from the extra cellular fluid. Reduced ECF, decreases blood volume which in turn increases cardiac load (less blood volume means your heart has to pump more often to get the same amount of nutrients and oxygen to working cells). Absorption of nutrients in the gut Sodium facilitates something called the sodium-potassium pump, this is the way the cells of our small intestine takes nutrients (glucose/carbohydrates, amino acids/protein and water) from the gut into the blood. Without appropriate sodium in in our body this pump does not work efficiently, hampering our ability to absorb nutrients (particularly those all-important carbohydrates whilst exercising). Nerve impulse transmission Sodium is the key ion that your nerve cells, a.k.a neurons, use to transport nerve impulses. Similar to the way an electrical current moves along a wire, a sodium current moves along nerve cells. Without adequate sodium levels in the body this process becomes less efficient and therefore signals from your brain and spinal cord don’t reach their intended target quickly and efficiently. These targets could be muscles, working organs and even inside the brain itself. We need all of these areas to be functioning well to perform at our best. Maintaining cognitive function Ever felt that “brain fog” toward the end of the day, or even a long race? It can come down to several factors but quite often a drop in sodium levels can be to blame. This occurs due to two of the factors discussed above – fluid balance and nerve impulse transmission. If there is a drop in sodium in the blood, osmolarity pushes increase fluid into the brain which, at low levels causes this “brain fog” along with headache and fatigue. More extreme cases, such as hyponatremia (discussed further in a later FAQ), can cause vomiting, nausea and death. As for nerve impulse transmission, our brain is a giant collection of neurons, so if these are not functioning well, our cognitive function will not function well. Muscle contraction Very similar to nerve impulse transmission, your muscle cells require movement of sodium ions (along with other ions such as calcium) to stimulate muscle contraction. Without sodium, your muscles cannot contract efficiently. Avoiding cramp The topic of cramp, particularly Exercised Associated Muscle Cramp (EAMC), has become a somewhat controversial topic in recent times. Truth be told, we don’t know the full story on cramp just yet, but there are two competing theories – the “Dehydration/Electrolyte Theory” and the “Neuromuscular Theory”. The former says that depleted electrolytes (mostly sodium) cause fluid shift in the body, that in turn causes the interstitial fluid areas to contract leading to cramp. The latter argues that electrical misfiring in the muscles causes an imbalance between excitatory and inhibitory signals causing localised muscle cramp. As with all many of these dichotomous arguments the answer probably lies somewhere in the middle. What we do know is that maintaining sodium levels does help avoid muscle cramps (whatever the mechanism). You can read a very in depth blog by Precision Hydration founder Andy Blow, about cramping here.

Question 3

Why should you personalise your hydration plan?

Accepted Answer

In short – no two peoples hydration needs are the same, therefore individualising your hydration plan for YOU, is key to maximising YOUR performance. The two main factors that will change from person to person is the amount they sweat (sweat rate) and the amount of sodium in their sweat. Everyone loses a different amount of sodium in their sweat; this can be as low as 200mg/l all the way up to 2000mg/l – a huge variance I’m sure you’d agree. The amount of sodium in your sweat is genetically determined and stays constant throughout life. Similarly, everyone will have a different sweat rate, but there are more determining factors to this than just genetics. Factors including type & intensity of exercise, ambient temperature, sex, age, humidity, clothing, acclimatisation, level of conditioning, airflow, psychological stimulation/excitation, hormone levels and hydration status can all effect how much we sweat.  A handy tool to document and (in time) predict your sweat rate for different sports in different conditions can be found here. What we can see from the above is that the amount of sodium we lose and the amount we sweat from person to person varies wildly, therefore a “one size fit all” approach to hydration just won’t cut it.

Question 4

Precision Hydration talks a lot about sodium, what about other electrolytes (e.g. magnesium, potassium), are they important?"

Accepted Answer

Whilst sodium is the main electrolyte an athlete should focus on in sweat loss, it is true that we also lose potassium, magnesium, and calcium in our sweat (these all play vital roles in bodily function and performance), so a fair question to ask is why the sweat test does not also measure these? It all comes down to the amount of these electrolytes that are lost. Average losses for these electrolytes are Sodium 1000mg/l (range 200-2000) Potassium 200mg/l Magnesium 12mg/l Calcium 20mg/l As you can see from these numbers, sodium is by far the dominant electrolyte lost in sweat (and also the most variable person to person), so that’s why we focus on it. Precision Hydration products will cover the loss of the other 3 electrolytes easily with each tablet or sachet containing 250mg/l of Potassium, 24mg/l of magnesium and 48mg/l of calcium when mixed as directed. Therefore these don't need to be measured. To put it simply – Precision Hydration products have been developed to cover losses of potassium, magnesium and calcium in sweat (this was very deliberate!!).

Question 5

Why do we sweat?

Accepted Answer

Human’s use sweating to maintain our internal body temperature. It is extremely important our internal temperature stays in a range somewhere between 36.5 and 37.5ºC – outside of this range can be dangerous for a myriad of reasons (including death!). When our core temperature starts to increase (such as when we are exercising), our body starts to sweat. When sweat evaporates off our skin, it takes away heat allowing us to keep inside the desired range (in cold conditions we shiver which has the opposite effect i.e. increasing our core temperature). Our ability as human beings to sweat is relatively unique in the animal kingdom – and we by far sweat the most of the few animals that do sweat (horses, camels and hippos are a few). In evolutionary terms, our ability to sweat is one of the reasons humans came to dominate the world. Sounds a bit far-fetched on first reading I know, but our ancestors were not blessed with the speed of our 4-legged prey back on the African savannah. This meant the only way for humans to catch our prey, who despite being very fast, could not sustain exercise for long periods (due to their inability to sweat), was to wear them down by chasing them for long periods until they became exhausted, a.k.a Persistence Hunting. Without the ability to sweat and offload the excess body heat, humans would not be able to hunt in such a way and therefore would not have survived and prospered as we have. Most animals, such as the prey mentioned above, reduce their core temperature through panting (think of a dog). This is a very inefficient way to offload body heat, but it does have the advantage of conserving fluid and salt.

Question 6

How do I determine my sweat rate?

Accepted Answer

Determining your sweat rate is a relatively simple exercise. In essence, it's how much you weigh before a session (A) minus what you weigh following a session (B) divided by the duration of the session (time). Sweat rate = (A – B)/time This can be complicated during long sessions as you are most likely going to be consuming fluids in session, so we need to factor this into the equation too. We do this by weighing our fluid pre (X) and post (Y) and then adding this to the equation Sweat rate = ((A + X) – (B + Y))/time This can be further complicated by needing to use the toilet during your session. The weight of these evacuations will need to be factored into the equation – and good luck getting an accurate weight for these – EW!!! To make this data as accurate as possible for you, it is advised to take these measures during a range of exercises (e.g. running, cycling, football), in a range of conditions (e.g. varying heat and humidity, indoor and outdoor) at a range of intensities (e.g. pace or power). Over time you will develop a great picture of yourself and how much your body sweats in many, varied conditions. To make things much simpler and easier to track, Precision Hydration have developed this sweat loss calculator. And for a deeper look at these calculations and how to best use the data, please read this blog by Andy Blow.

Question 7

Why is water alone not enough for hydration when exercising?

Accepted Answer

Only drinking water for rehydration does not replace everything you lose through your sweat, in particular, sodium. This becomes an issue the longer exercise goes on as the more you sweat, the more sodium you will lose. People can lose anywhere between 200 and 2,000mg/l of sodium in sweat, and this needs to be replaced to an adequate level for each invividual (the number one reason all athletes should have their sweat tested is to detemine this number). The main issue with this is that it will upset the fluid balance in your body by diluting the electrolytes. This leads to dehydration (low sodium means your body can’t retain water, you just urinate it out) and deminished abilty to conduct nerve signals and contract muscles. In extreme cases, hyponatremia (hypo = low, na = the chemical symbol for sodium, tremia = in the blood) may be experienced, which at low levels can lead to fatigue and brain fog, at worst can lead to nausea, vomiting and in extreme cases, death.

Question 8

How can I tell if I'm dehydrated?

Accepted Answer

The only sure-fire way to test your hydration status is through scientific tests such as blood samples and radioactive isotope tests – neither of which are handy in real world scenarios. Chronic/longer term dehydration  The WUT system (W = Weight, U = Urine, T = Thirst level) developed by the US army is a user-friendly, real-world tool that can be utilised to get a gauge of your hydration. All measures should be taken first thing in the morning Weight Is your weight 2% or more less than your regular body weight? Yes = 1 point, no = 0 points. Urine* What is the colour of your urine? Dark = 1 point, Light = 0 points Thirst level Are you thirsty? yes = 1 point, no = 0 points Scoring 1 point = Unlikely you are dehydrated 2 points = You are somewhat dehydrated – address this before training for the day, particularly if you have intense training planned 3 points = You’re almost definitely dehydrated – it is essential this is addressed before training for the day. *We’ve all seen those pee colour charts right? Whilst they have been popular for a while, used in isolation the colour of your urine is actually a poor indicator of hydration status. This is because the colour of your urine can be affected by several things, especially what you have eaten that day (if you don’t believe me, take a berocca and go for a wee about an hour later). Acute Dehydration A drop in body weight  There is conjecture in the current literature in regard to this, with different athletes being able to handle different levels of dehydration - old school thinking says 2% loss in body weight, but up to 7% has been shown to be tolerated. On an individual level this will be determined over time when matching up how your body feels/is performing with different levels of body weight loss.  An increase in heart rate  Have you seen a sudden increase in your heart rate during a steady state of exercise? This may be an indication of dehydration. Our body draws sweat from extracellular fluid, which inturn draws fluid from our blood - causing a drop in blood volume. Our blood is what carries oxygen and nutrients to our working muscles, if the volume of your blood drops our heart has to beat faster to deliver the same amount of oxygen and nutrients to the body. Imagine you were filling a 2L bucket with water using a 500ml glass, but only had 2 minutes to fill it - only 4 trips from faucet to bucket required. Now imagine you only had a 250ml glass and still only 2 minutes to fill the bucket - 8 trips are now required. In this example the glass is your blood and the trips are your heart beats - double amount needed to deliver the same amount to the end target! Fading and Cramping Whilst not solely down to just hydration status (fuelling and general conditioning also play a massive role), fading and cramping at the back end of an event, particulalry in warmer conditions, can be an indication of dehydration.

Question 9

What is Hyponatremia? What causes it? And why is it so dangerous?

Accepted Answer

Hyponatremia is low sodium levels in the blood (hypo = low, na = the chemical symbol for sodium, tremia = in the blood). It is most often caused by drinking lots of water without electrolyte replenishment. This often occurs prior to a big race where people want to be hydrated and ready to go on the start line. Maintaining sodium levels in the blood is extremely important as it maintains fluid balance and is also vital for nerve impulse transition and muscular contraction (i.e. anything electrical in the body! It's in the name electrolyte).  The reason hyponatremia is so dangerous is because it upsets fluid balance (fluid is drawn from the blood into the interstitial fluid, basically meaning there is less blood volume leading to cardiac strain), reduced nerve pulse transition (nerve impulses are vital for cardiac contraction, muscle stimulation and cognitive function) and reduced muscular contraction (reduced muscular contraction means our heart cannot beat efficiently and skeletal muscles cannot contract to move us). At low levels, hyponatremia results in fatigue, brain fog and reduced physical performance, as it worsens it can lead to nausea and vomiting and in the worse case scenario, death.

Question 10

Sodium is part of regular table salt, can’t I just get my sodium needs from that?"

Accepted Answer

Theoretically yes, practically....not so much. Regular table salt is sodium-chloride, chemical symbol NaCl. What this doesn’t tell you, is that only 39% is sodium. Whilst a well balanced and varied diet will provide you enough sodium for your day-to-day needs, it is very unlikely it will provide enough for your exercise needs, especially as you start to sweat. As the exercise goes longer and longer, sodium will need to be replenished. If you were to try to use just table salt for this (e.g. if you added it to water) it unfortunately would be 1) unpalatable, and 2) quite harsh on your stomach. To highlight this, the average triathlete sweats out a little under 1000mg/l of sodium. To get this from table salt, around 2.6 grams or half a teaspoon of table salt would have to be used (1 gram = 1000mg, only 390mg of which is sodium, 390 x 2.6 = 1000mg of sodium). If you give this a go, you will soon realise it taste somewhat like sea water (yuck), and if you’ve ever been unfortunate enough to swallow sea water you will appreciate that your tummy generally does not react well to it! Further to this, our body requires more electrolytes than just sodium and unfortunately regular table salt will not provide the magnesium, potassium and calcium that is also required for performance.

Question 11

What does the Advanced Sweat Test involve? Is it invasive?

Accepted Answer

The Advanced Sweat Test is a non-invasive procedure that that is pain free, and for the rare person, mildly uncomfortable. The equipment used is the same equipment that is used by medical professionals to test for Cystic Fibrosis. Firstly, a gentle chemical solution and a sweat inducer (2 small electrodes) are placed on the forearm stimulating a small patch of sweat. Following this, we collect the sweat using a macroduct and run it through an analyser, which tells us exactly how much sodium you lose in your sweat. When we combine this with what you have told us about your training, we are able to develop your personalised hydration plan which is sent to you through Precision Hydration's online system (you will always have access to this plan). From go to woe this whole process takes around 45 minutes. A video of the testing procedure can be found here.

Question 12

Can I train on the day of my test?

Accepted Answer

Yes, there is no issues with training before or after your test.

Question 13

What should I eat or drink before my test?

Accepted Answer

There is no need to eat or drink anything specific before your test.

Question 14

Will I need to exercise during the test?

Accepted Answer

No, the test is very passive and exercise is not used to induce your sweating (this is what sets us apart from other sweat tests out there).

Question 15

Is the test expensive?

Accepted Answer

The answer to this is relative, but in Australia tests will be in the range of $200-$250, depending on location and whether we have to come to you. This is a one off cost for the test, you will only ever need to have your sweat tested once (the sodium levels of our sweat do not change over time).

Question 16

How often do I need to have my sweat tested? Does my sodium loss rate change over time?

Accepted Answer

You will only ever need to have your sweat tested once. The sodium levels of our sweat does not change over time.

Question 17

Can you send me an “at home” test?

Accepted Answer

No, the advance sweat test needs to be done face to face. Alternatives to this are a home visit test where we come to you (a cost will be incurred for travel) or Precision Hydration offer an online sweat calculator. This is not as accurate as the advanced sweat test but it is a data guided alternative if the advanced sweat test cannot be accessed.

SWEAT PHYSIO

SWEAT PHYSIO