Hydration Blog

How to stay hydrated during the MdS

Sunday, November 15, 2015

How to stay hydrated during the MdS

Alongside pacing and foot care, hydration is one of the most important factors behind success at the MdS. Luckily, it’s something you can get ahead of before you arrive in the desert, simply by gaining a better understanding of the issues you’re likely to face and by having a plan for how you’ll manage them.

Why is hydration so important?

Your blood has multiple roles to play when you’re exercising hard…

1.  It has to be directed to active muscles to supply them with oxygen and energy; and to remove toxic byproducts that would otherwise accumulate.

2.  More of it than usual has to be sent to the skin to help dissipate heat and keep your core body temperature in check.

3. You need to sweat to increase the effectiveness of this heat transfer from your skin to the environment, and sweat is drawn directly from your blood plasma.

Dehydration increases the stress your body is under during these processes and  so hampers performance. That’s why maintaining body fluid and electrolyte levels during exercise is critical. This is especially true in hot desert conditions, where heat dissipation is more difficult and fluid loss dramatically increases.

How worried should I be about being dehydrated at MdS?

Whilst hydration is clearly important for maintaining performance, there are a few things to bear in mind…

1.  Getting somewhat dehydrated is almost inevitable for most people on the move under the midday desert sun. Your sweat rate can be as high as 2-3 litres per hour, whereas your maximal fluid absorption rate is likely to be only 800ml-1 litre per hour. You don’t need a maths degree to realise you’re likely to be fighting a losing battle when it comes to fluid loss.

2.  A certain degree of acute dehydration during stages is not necessarily as bad as you might think. Whilst some widely reported studies in the past suggested that losing as little as 2% bodyweight via dehydration can hamper performance significantly, more recent analysis of athletes in competition settings has shown that many can continue to perform well at 4-6% dehydration, with some elite athletes (such as marathoner Haile Gebresallassie) finishing races in world class times whilst nearly 10% dehydrated! This is not to say that dehydration won’t derail your event if you don’t pay attention to the risk, it absolutely has the potential to do so. Just that, when dehydration occurs acutely (and at relatively moderate levels) during exercise it might not be quite as detrimental to performance as was once thought.

So, should I just drink as much as possible during the event?

Forcing down large amounts of fluid even if you really don’t feel like it is not going to help. So, keep in mind that, just because you are issued a large amount of water each day, this doesn’t mean you have to drink absolutely all of it.

So, how much is enough? It’s reassuring to remember that you have a pretty powerful, innate ally in the fight against dehydration; your thirst instinct. If you pay attention to your body’s own signals and respond to the early signs of thirst you’re unlikely to get horribly dehydrated in a hurry. Yes, you’ll need to be aware of the need to drink more than you normally would when training in the UK, but that doesn’t mean you should stop listening to your body altogether.

The reason to avoid mindless drinking is that excessive fluid consumption can have some pretty nasty effects on your performance and health. You may well have heard of ‘hyponatremia’ as the condition has got more and more press coverage in the last few years. The word literally means “low (‘hypo’) blood sodium (‘natremia’)” and most often results from consumption of fluids to an extent that you actually dilute the concentration of sodium in your blood stream to dangerously low levels. Sodium is an electrolyte critical for a variety of functions in the body, including maintenance of:

  • Cell membrane potentials
  • Nerve impulses
  • Muscle contractions
  • Fluid balance

If you drink far more than you need (without replacing sodium adequately through the foods you eat, or the fluids you take in) it can have very serious side effects. In an effort to maintain blood sodium levels in the face of water overload, the body shifts fluid from the blood stream into its own cells, causing them to swell up. At first this might just result in some slightly swollen fingers, ankles and a general feeling of malaise and lethargy. But, if allowed to progress, can also result in swelling of the brain, headaches, coma and even death in extreme cases. This is a partly why you will be issued with salt tablets with your ration of water at MdS; taking in adequate sodium along with the fluids you consume is helpful in maintaining levels in your blood stream.

The key is to…

1.  Keep your fluid levels reasonably topped up during each stage, whilst…

2.  Being realistic that much of your re-hydration will have to be done between stages.

What about electrolytes?

  • Electrolytes are a big part of the hydration equation simply because you lose a lot of them in your sweat.
  • The main electrolyte you lose in your sweat is sodium. It accounts for around 90% of the ions lost because it’s prevalent in your blood plasma, the pool from which sweat is drawn.
  • It is true that you do also lose some calcium, magnesium and potassium, but in relatively trivial amounts, so sodium replacement should be your main focus when it comes to electrolyte replenishment.
  • Sodium replacement helps you maintain blood volume, which in turn helps with management of your core temperature and delivery of blood to working muscles and the skin.
  • Because you lose a relatively large amount of sodium in your sweat, when you’re going at it hard for several hours at a time total sodium loss can be really high. Therefore a reasonable level of supplementation is usually required alongside the fluids you consume in order to keep the body balanced.
  • The interesting thing about sodium loss in sweat is that it varies dramatically from person to person, with some people losing as little as 0.2g per litre of sweat and others losing near 2.0g per litre! This means that different athletes need to take in very different amounts of sodium when sweat output is high. This variance in sweat sodium loss is largely down to genetics. Whatever the cause, it’s clear that a ‘one-size-fits-all’ approach to electrolyte supplementation doesn’t work.

How can I understand my personal hydration needs?

This is something you can do either through trial and error, or by having a Sweat Test.

The ‘trial and error’ route

Key signs that you might be in the ‘high’ or ‘very high’ sweat sodium loss category are things like…

  • Seeing large salty deposits on your skin or clothing after exercise
  • Your sweat tasting salty or stinging your eyes
  • Regularly getting muscle cramps during long exercise sessions
  • Craving salty food during or after sweating a lot.

If you tick any of those boxes, then it’s worth experimenting with more aggressive sodium intake strategies before, during and immediately after exercise to see what effect it has on your performance and recovery.

The ‘Sweat Test’ route

If you prefer a more comprehensive, scientific approach then we offer a sweat test (available at the MdS expo again this year, or through one of our test centres).

How can I maintain electrolyte levels during the MdS?

You can replace the sodium you lose during the event in a variety of ways…

1.  Through your food. Re-hydrated processed foods contain lots of sodium, so things like ration packs are a great way to replenish electrolytes between stages, as is snacking on salty foods during the day.

2.  Taking some of the salt tablets issued at the event to top you up whilst on the course.

3. Taking your own hydration tabs or capsules with your water. The advantage of this over taking the standard issue salt tablets is that you can more accurately measure the amount of sodium you’re taking in, meaning you can tailor your intake to your personal needs. Basing your intake on the levels that have worked for you in key training sessions and build up events is likely to be highly effective. This is why devising and optimising your hydration strategy should be high on your priority list over the next few months.

I hope this post helps you get started with your hydration plan. We’re also giving a free hydration workshop and have a stand at the MdS Expo, so if you have any questions about hydrating at the MdS, come and see us. Or email us at info@precisionhydration.com.

Andy Blow


Precision Hydration


Sodium pre-loading

Friday, August 15, 2014

An interesting study into pre-loading with sodium rich drinks before exercise….

Sugihara and colleagues have just published online in the European Journal of Applied Physiology (link to paper here) their 8-subject study that looked into the effect of ramping up the sodium content of a drink on hydration status. The hypothesis being that if the athlete is hyperhydrated with a higher sodium drink then performance increases. Or at least performance degradation is slowed. The drinks used were of fairly high sodium content (1380mg/L, 2760mg/L and 4140mg/L) when you consider sea water is around 10,000mg/L, Gatorade is 450mg/L while Powerade stands at 225mg/L.

The results supports previous work that showed the higher sodium drinks induced hyperhydration with an increase in plasma volume and net water gain. But the higher levels of sodium in the drinks also induced diarrhoea and gut upset. Not pleasant if you're competing and in fact defeats the purpose of taking the drinks in the first place. 

What is interesting from our point of view was to see was that the 1380mg/L drink, at 90 min after consumption increased plasma volume compared to water and that the net water gain was maintained at 120 - 150 min after ingestion, without causing excessive gut issues.  So overall it suggests that there is no great need to take sodium in really high quantities, and that using H2Pro Hydrate 1500 (1500mg sodium per litre) as many athletes do to enhance pre-event hydration, should be sufficient. 

Individualisation - the key to optimal hydration?

Friday, June 28, 2013

Individualisation - the key to optimal hydration?

Having come across 2 interesting articles in the mainstream Running and Triathlon press recently we thought it was a good time to put up a post about just why individualisation is so important when looking at hydration.

First up; a great article by TJ Murphy on Triathlete-Europe entitled 'Does Dehydration Improve Performance?'


In the article TJ highlights the case of legendary triathlete Scott Molina who famously struggled at the Hawaii Ironman as he battled dehydration, hyponatraemia and pacing issues for years that preventing him from winning the event, despite being amongst the favourites to do so.

He also explores the conclusions in Dr Tim Noakes' 2012 book, 'Waterlogged' that suggest most athletes tend to over, rather than under consume fluids during exercise and that this is largely as a result of the marketing hype created by drinks companies keen to drive up sales of their products. 

We think that one of the best things about this article is the fact that it does acknowledge that whilst Dr Noakes is likely to be very correct in his assertions that a lot of athletes do over drink (thanks to the efforts of the industry to encourage this habit), Murphy also points out that for an individual like Molina who reportedly had a sweat rate of up to 3 litres per hour(!) working out what you need in your own circumstances is the key to optimising your own performance. 

As it turned out in the end Molina did some great homework to understand his own physiology better and came up with an individualised approach to fluid intake and pacing that eventually allowed him to go on and win the Ironman in 1988.

The article closes with a fantastic quote suggesting that "Everyone keeps searching for some perfect answer for matching hydration and performance, but perhaps Mucky Sludge [Scott Molina's nickname] blazed the path for us long ago. We each have to figure this out for ourselves."

The other article is on pg 27 of the latest UK Runners World magazine (August 2013) and highlights the case of Ultra marathon runner Sophie Power who drank herself into a dangerously hyponatraemic state in a multi day race. This was despite that fact that she was taking 'electrolyte' tablets that turned out to actually have a very low sodium content. She was lucky to survive the incident due to the quick thinking of the event medical team but others have tragically lost their lives in similar circumstances. 

So what does all this show?

Well, we think that understanding your own hydration needs based on factors including your own sweat rate, sweat sodium concentration, the length, intensity and environmental conditions of your training and races is key to determining what will best work for you. With some intelligent preparation, research and organised trial and error you can find a hydration and electrolyte strategy that will help you to perform at your best and stay healthy. 

In essence it's exactly why we are making sweat testing more widely available to athletes and producing the only multi-strength range of electrolyte drinks in the world - H2Pro Hydrate - so people can tailor their replacement strategies more closely to their own needs. 

Cramping and Electrolyte Loss - what is the link?

Monday, March 18, 2013

We get asked all of the time about whether electrolyte replacement (particularly sodium) can help with athletes who get cramp. It is always frustratingly hard to explain why sometimes electrolyte supplementation can be like a complete miracle cure for cramps in certain people, however for others it does not help much at all....

We believe it is likely to be because although electrolytes are implicated in some instances of muscle cramping, many other factors such as fitness level, fatigue and the type of movement patterns being undertaken can also be the cause.

In terms of our own experience in the field with 1000's of athletes we tend to find that a more tailored approach to sodium replacement (with drinks closely matching sweat composition, taken to thirst) reduces incidences of cramping in those who tend to suffer cramping late on in endurance events or in competitive games/matches/tournaments after prolonged periods of sweating. This effect tends to be magnified in hot weather or when intensity is very high, and is more pronounced in athletes with high sweat sodium concentrations and/or very high sweat rates. We have also noted some anecdotal experiences of athletes who used to suffer with cramps when taking in high volumes of plain water or low sodium fluids (because they were scared of becoming dehydrated) - and these athletes often see a reduction in cramping when they have either reduced total fluid intake to more normal levels or taken in additional electrolytes with fluids (or a combination of the two). 

Results with athletes who cramp at seemingly random times tend to be less positive (when using sodium supplements alone) - however programmes of targeted stretching, sports massage, more progressive training overload and general dietary improvement can be helpful in reducing the likelihood of cramping occurring in these individuals.

Because of all this we thought we'd share a review article that does a very good job of explaining the possible links between cramping/fatigue and sodium depletion - and it is well worth a read if you are interested in finding out more about the topic as a whole.

The reference is: 

Bergeron, Michael F. “Muscle Cramps during Exercise V Is It Fatigue or Electrolyte Deficit?” Current Sports Medicine Reports: Supplement-Sodium Balance and Exercise 7.4 (2008)

And the full article can be read of downloaded from this link

A genetic reason for why some people lose more salt in their sweat than others?

Wednesday, November 21, 2012

A genetic reason for why some people lose more salt in their sweat than others?

We recently came across an interesting study from the USA which offers a very good explanation of why some people are high salt sweaters and others low or normal.  This group in question biopsied the skin of 3 groups of people - those with cystic fibrosis (known to have high levels of sodium and chloride in their sweat), those with high sweat sodium levels but not CF sufferers and those with normal sweat sodium levels.  Those with CF and high salt sweaters had a lower abundance of a protein called cystic fibrosis transmembrane conductance regulator (CFTR).  This protein is responsible for absorption of chloride and sodium in the sweat gland so a lower level means less is absorbed back into the blood and more is excreted out in sweat.  


Brown MB.  Low abundance of sweat duct Cl channel CFTR in both healthy and cystic fibrosis athletes with exceptionally salty sweat during exercise.  Am J Physiol Regul Integr Comp Physiol. 2011; 300: R605–R615

More Evidence For Drinking To Thirst, as well as consuming electrolytes, especially if you lose a lot of salt in your sweat....

Wednesday, October 31, 2012

More Evidence For Drinking To Thirst, as well as consuming electrolytes, especially if you lose a lot of salt in your sweat....

Reading Tim Noakes' book "Waterlogged" does make you think hard about whether one should simply respond to their thirst stimulus rather than try to replace lost volume. I generally do agree with this idea (it seems quite a lot of athletes make the mistake of drinking too much pre, during and post exercise) although do disagree with his observation that sweat sodium levels do not very dramatically between humans. There is in fact plenty of evidence that there is a massive variation (infact in a later blog I will describe the genetic basis for the variation that results in lower number abundance of a protein called CFTR).
Just recently while trawling the sea of evidence related to this topic I came across a study done in Georgia, USA in 2011.  The group looked at thirst responses in cystic fibrosis (CF) suffers, non-CF active people with high sweat sodium levels ('salty sweaters') and controls with average sweat sodium levels. After forcefully dehydrating them by 3% of their body weight in a heat chamber they showed that thirst responses were equal across all groups.  They concluded that the thirst mechanism is maintained despite the large variation of sweat sodium losses, blood osmolality and plasma volume between the groups.  They concluded, relevant to our fundamental principle of sweat sodium replacement, that "....sweat Na+ losses observed in SS (non CF but high salt sweaters) and CF provide empirical support for models and recommendations for consuming electrolytes during prolonged exercise to guard against the potential for hyponatremia in salty sweaters..."

So in agreement with Noakes, drink to thirst. No matter what your sweat sodium losses your thirst appetite will be preserved.  But drink what you lose.

Dr Raj Jutley. 

Brown MB et al. High-sweat Na+ in cystic fibrosis and healthy individuals does not diminish thirst during exercise in the heat.  Am J Physiol Regul Integr Comp Physiol. 2011; 301: R1177–R1185

Placebo effect?

Thursday, July 26, 2012

We received the email below from a customer a few days ago and thought it would be a good idea to share his question our response and his subsequent reply online - especially given the amount of interest there has been in sports drinks since the BBC Panorama documentary highlighting the British Medical Journal's latest thinking on sports drinks was aired on July 18th....

We'll follow on with a more in-depth comment on the BMJ article and also on Dr Tim Noakes' book 'Waterlogged' soon. 


Hi Guys,

I would be interested in your thoughts on the lack of need for hydration products as currently proposed by Tim Noakes. He says there is no need for anything like this. He also says that sweat with high levels of sodium are just because of high intakes of sodium and to cut this out also means that the sodium levels in sweat will in turn drop. I went to the talk at all 3 motion and have been using your products and have got on fine so far but I’m wondering if this is placebo or not?


Our response:

Thanks for your email.

It's a very interesting question, one that we're being asked more and more here is our take on it: 

Firstly whilst we have a huge amount of respect for Tim Noakes and his work he has a record of being quite provocative in his approach to certain topics. He likes to challenge exists dogmas and this is both healthy and necessary in science. However, sometimes he adopts quite an extreme position (in this case that sports drinks are completely unnecessary and that the companies that sell them are conning us) partly, I think, to get people to sit up and take notice and this certainly works!

For starters we do agree with his point that listening to thirst is a good idea. Too many people do force fluid down too frequently and suffer as a result and in our advice to athletes we take a similar position. 

However, one of the main points that we'd disagree with in his new book is in the way it dismisses that there is a large variation in sweat sodium losses; saying that they are relatively similar between people and mainly driven by dietary sodium intake. Our own data (which is probably one of the most comprehensive sets available) shows a much wider variance in sweat sodium values (approximately 19mmol/l to 84mmol/l) in well trained athletes than he quotes in the book (around 20-40mmol). 

It's certainly possible that at the extremes when people are taking in huge volumes of sodium, or virtually none at all, the body could respond by losing more or less in sweat but the fact remains that the main mechanism for regulation of sodium is in the kidneys absorbing or excreting more in urine. From the large numbers of people we have tested (some of whom in professional rugby and football teams all eat similarly controlled diets to one another yet still show this wide variation in sweat sodium levels) it is clear there must be something other than just sodium intake dictating sodium loss in sweat and it would appear that this is genetics. 

On a personal level as I explained in the talk at All3Motion one of the biggest drivers for me in getting my own sweat tested many years ago and looking into this topic further was that I had found by trial and error that by taking in lots of sodium in races I a) stopped cramping (as I had done a lot beforehand) and b) generally my performances improved dramatically. The consistent way in which this happened (and from listening to the experiences of other athletes we've tested and talked to over the years) leads us to strongly believe it cannot just be put down to a placebo effect.

Also, although Dr Noakes is very sure in his opinion that sodium loss has absolutely nothing to do with cramping a lot of anecdotal evidence would suggest otherwise. For sure we don't believe it to be the only factor involved but the amount of athletes who have stopped cramping when we've upped their sodium intake in endurance events is significant. Again our own data from sweat tests and questionnaires shows a statistically significant correlation between athletes who report that they cramp regularly and the fact they tend to have higher sweat sodium levels. This may not offer definitive 'proof' of a link but it ties up with enough anecdotal experience to be taken seriously.

As with a lot of topics in science and sports performance if you search hard enough you can definitely come up with a lot of evidence to prove and disprove most theories. Do we agree with Dr Noakes that many of the big sports drink companies have 'hyped' the efficacy of their products in order to sell more of them? Absolutely. Do we think that there is no benefit to be derived from intelligent use of certain supplements (such as sodium) to prevent performance dropping off as the body gets depleted during extended periods of exercise? No. 

Kind regards


Subsequent reply:

Thanks for the very detailed reply. It’s refreshing to get that sort of detail.

For my experience with your products I have not suffered any cramps this year since I started taking them. 

This year I have run Ultras, 40, 50 and 100 miler and all using your 1000mg product. I found they helped with hydration and absorbtion of food which is something that I think gets little coverage and is vital.

In the Cardiff 50 this year at mile 46, I came across a guy who could not stand, let alone walk due to massive cramping.  He was actually trying to call his wife as he was going to withdraw as he was in so much pain.

Luckily for him I had your tablets freshly prepared from the last aid station and I made sure he drank the majority of my bottle, I left him alone to deal with his pain and carried on hoping that he may be able to stumble the remaining 4 miles.

Well I'll be! He came flying past me about 10 minutes later saying I had saved him and the drink was an elixir of life! This really pleased me but because I was now being beaten by Lazarus I had to step up my game as there was no way I was going to be beaten by someone who was practically DNFing 10 minutes earlier. Needless to say we both finished in just over 8 hours and I did beat him and came 28th. He was all over me with emotion at the finish line and kept telling everyone he could how I had saved him. In fact it was your product that saved him I just happened to have some ready and was willing to share.

I used it on the 100 I finished 2 weeks ago and has no issues at all although my ankle did swell up like crazy due to terrain etc but I finished in 24.08 and beat myself up for ages for not going under 24 hours but I knocked 2 hours 27 off my 85 mile time from 2 years ago and ran 15 miles further and on harder terrain and elevation so that cant be bad! I have also got my mate Max Dillon who came 3rd at Cardiff on to the product and he loves it too and has had no issues.


Creative uses of H2Pro Hydrate.....Nutrichef add them to a smoothie...

Friday, May 18, 2012

We thought we'd share this one. 

We hear of people using H2Pro Hydrate tablets in some creative ways from time to time; adding them to carbohydrate drinks to boost the sodium content or mixing them in 50/50 with flat coke and water to create a very effective caffeinated, carb drink for racing. But this is definitely the most sophisticated use we've come across so far. 

What's more it's from a very well respected source in the world of nutrition; Barbara Cox, CEO of Nutrichef (who incidentally you can follow on twitter @NutriBarbara), and she's been adding it to her smoothies....Thanks for the heads up on this Barbara....

H2Pro Smoothies:

Dissolve 1 table in 500mls water

Add 1 banana

Add handful of strawberries and blueberries

1 tbsp Chlorella (sea algae for protein)

1 shot wheatgrass juice (I use live frozen wheatgrass shots)

Whizz all together in the blend and voila….gorgeous!

It sounds like a really good post exercise recovery drink (plenty of carbs from the fruit, fluids and electrolytes from the H2Pro Hydrate and water and some protein) We're going give it a try once we figure out where to get some Chlorella from!

H2Pro Hydrate at the Patrouille Des Glaciers

Thursday, May 10, 2012

The Patrouille Des Glaciers (PDG) is one of the worlds toughest ski mountaineering races. Held every 2 years in the Alps near Zermatt, Switzerland it is an event with military origins and in 2012 a group of British soldiers headed out to take on the challenge - using H2Pro Hydrate to keep their fluids and electrolytes topped up in a very harsh, unforgiving environment. This is what they had to say about their experience:

"Despite having limited time to prepare we used H2Pro during the flight to Switzerland 48hrs prior to the race which undoubtably helped with our basic hydration. During our training day before the race we tested the race concentration to confirm suitability. Not only did the product keep us hydrated during a long and arduous day but I'm convinced it helped us adjust to the altitude and acclimatise quicker. Although the race was stopped due to avalanches I am sure H2Pro mitigated our lack of environmental training and acclimatisation."

Hydration at high altitude can be an issue due to the dryness of the air and sweat losses whilst ski mountaineering can be very high as it requires a lot of clothing to be worn to protect against the elements yet work rates are very high. Having H2Pro Hydrate in the water they were carrying also helped to stop it freezing up in sub zero temperatures.

We will be supporting the British team in 2 years time when they will get a second chance to take on the PDG - hopefully this time without the avalanche risk that cut this years race short. 

Lee Shannahan with his H2Pro Hydrate and the Matterhorn in the background:

The Ultimate Sport Drink? Possibly not.....

Tuesday, April 24, 2012

We were interested to read an announcement that someone in the US has created the "ultimate sports drink" with its own spin on the ideal electrolyte mix

This time, the EX5 drink puts in a much higher level of potassium than seen in most sports drink - in fact 7x higher than Gatorade and almost 9x higher than Powerade.  It's an interesting concept because unlike appropriate sodium supplementation, nowhere in the scientific literature has it ever been demonstrated that potassium supplementation in sports hydration confers any benefit.

What's more, average sweat losses of potassium are 150 mmol/L so it would take around 16 litres of sweat to become potassium deficient and that's not likely to happen in a typical training session or race no matter how hot it is if you're eating a regular diet.  We're not really big believers in this one.......not with a potassium load that high and a sodium load of only 5 mmol/L.  The lowest sodium loss we've tested in over 300 tests done in house on athletes is 19 mmol/L so there is no way EX5 will replace losses of the lowest salt sweater....