Hydration Blog

Sweat, sodium, sea and surfski

Saturday, February 11, 2023



This recent article on surfski.info really jumped out at us for a couple of reasons; firstly because a few of us at Precision Hydration have got into this exciting and growing sport in the last few years and secondly because it ties in so appropriately with what we’re trying to do with our sweat testing and H2Pro Hydrate drinks.

To set the scene: International long distance surfski racing pulls together some of the best flatwater kayak paddlers in the world, many of the greats of surf lifesaving and a small but talented band of professional full time Surfski paddlers from around the world.

Races take place over distances from about 10km up to 50km on the ocean in very fast but unstable boats, with paddlers constantly chasing waves to increase speed and push for the lead. Often the environment is hot (Australia, South Africa, Middle East) and the races can last upwards of 2hrs – exposing the paddlers to a lot of heat stress and sweat loss. ‘The Doctor’ in Perth at 27km is one of the major events in the surf ski calendar.

In the 2012 Doctor Tim Jacobs (Pro Aussie ski paddler) and Australian surfski racing legend and Clint Robinson (also an Olympic Gold Medallist in from 1992 amazingly challenging for a spot in the Australian team for London 2012!) were duking it out for the lead with Jacobs eventually taking the win and Robinson dropping back to just 7th near the end.

It’s interesting to note that Clint was leading for a good part of the race but towards the end was losing power and starting to get cramp in his forearms; symptoms that often accompany electrolyte depletion. In his post race interview Tim credited the fact that he’d been taking sodium capsules before the event to load up on his electrolyte stores and maybe that had made the crucial difference? Even Clint said he’d consider taking them next time having talked to Jacobs after the race….

What do we think happened?
It does seem likely that Clint’s cramps and slow down could have been electrolyte depletion related due to the hot conditions and high intensity of the race…See this Gatorade article about the link between cramping and sodium:

Although Tim’s sodium tablet approach got through the day this time around it is still something of a hit and miss approach using those things – especially given the risk of gastrointestinal upset that can occur if you get the tablet/fluid intake wrong or take too many capsules….

What we also don’t know too is how much difference there is between the amount of electrolyte and fluid they are both losing when racing see this article that highlights the potential differences.

So if Clint did decide to copy Tim’s regime next time round there’s nothing to say it would work as well for him, given his own physiology…

The huge differences we see in sweat sodium levels across the population

Our position? – with a quick test to identify their own unique sweat physiology and appropriate electrolyte replacement both Tim and Clint could be replacing exactly what they need during the race. Leaving Clint to finish as strong as he started it and Tim to finish without the risk of gastrointestinal issues associated with popping salt capsules as well as avoiding the long-term health risk of taking excess sodium.

We’ll bring our sweat testing kit to the European races if you’re there guys!

How can a sports drink possibly hydrate better than water?

Saturday, February 11, 2023

On 4th January 2012, the Advertising Standards Agency (ASA) met to consider complaints that Powerade ION4 as advertised by Jessica Ennis, World and European Heptathlon Champion, was making claims that were misleading.  According to the advert and Ennis’ testimonial it was claimed that Powerade ION4 ‘hydrates (me) better than water’.  The ASA considered evidence from Coca Cola Great Britain as well as published scientific evidence and experts and the hydration claim was accepted (see http://www.asa.org.uk/ASA-action/Adjudications/2012/1/Beverage-Services-Ltd/SHP_ADJ_156530.aspx for adjudication details.

How can anything possibly hydrate better than water? Surely hydration and water are synonymous? While intuitively one would think so, it’s not that simple.  For the body to be better hydrated the drink has to retained by the body.  When comparing to another drink this can be shown simply by an increase in body weight with less urine production.  A more complex method using blood sampling (Dill and Costill method) is used to show an increase in plasma volume.  The benefits of improved hydration in sport are indisputable, especially in the context of intense exercise as Coca Cola GB took great pains to explain during the adjudication.

Almost all scientific trials looking at which drink hydrates better involve a cross-over design.  An athlete is randomly exposed to one drink and tested under controlled conditions with a standard exercise regime often in a climate chamber.  The test is then repeated usually 2-3 weeks later with the second drink being evaluated.  Quite a few such trials have been published with convincing evidence that electrolyte containing drinks result in better retention as evidenced by increased body weight and plasma volume. The electrolyte responsible for this retention is sodium – in fact the only electrolyte so far recognized scientifically to confer any benefit in rehydration. The drinks also tend to typically contain around 6% carbohydrate for energy as well as promote water uptake in the gut.

Our own Precision Hydration trials in elite athletes have replicated these findings. 72 hrs ad libitum drinking of an electrolyte drink specific to sweat sodium losses compared to Evian water showed that our electrolyte drinks (H2ProHydrate) containing zero carbohydrates resulted in a weight gain of around 0.72 kg (1% increase) with the greatest fluid retention seen in those who lost most salt in their sweat (1.72%).  One would think that weight gain translated to poorer performance. But as published scientific evidence has shown, this increased fluid retention results in improved performance.  In our trials we saw a 7.3% power output increase across all the athletes while on H2ProHydrate with peak gains of 23% seen in high salt sweaters who retained the most fluid.

All in all the addition of electrolytes, primarily sodium, to water makes it a better hydrator than water alone by a magnitude of around 11-20% (although claims of up to 40% have been made by some).  Being better hydrated increases weight slightly but the performance gains seen far outweigh this.

So it is good to see that sometimes sports drink marketing messages are more than just hype – although the fact that people contest marketers claims so vigorously in court does go to show how much mistrust there is of advertising these days….even when it is telling the truth!

Dr Raj Jutley
Chief Medical Office

Salt Friend or Foe

Sunday, January 29, 2023

I was forwarded this article the other day http://www.ericcressey.com/sodium-intake-is-salt-bad-for-you and thought it was time to respond to the question ‘Is salt bad for us?’ as it is something I get asked about very frequently; especially in relation to sports people. Whilst there’s never going to be a totally conclusive answer my thoughts are laid out below…

Salt - Friend or Foe?

In my role as a medic almost everyday I tell patients that their coronary artery disease is down to 5 major risk factors - high cholesterol, diabetes, smoking, high blood pressure (hypertension) and genetics. Some have all risk factors and some have none. But almost all who have hypertension are on a low salt diet. Imagine how shocked they would be if they looked at published scientific evidence and discovered that in fact a low sodium diet actually gives them a HIGHER risk of dying from cardiovascular disease? The US-based National Health and Nutrition Examination Survey (NHANES I) study published in 1998 showed that a low sodium diet is associated with a 20% higher risk of death. The NAHNES II published in the Amercian Journal of Medicine much later http://www.jhsph.edu/bin/s/m/May_9_2006.pdf went to on show that an intake of less than 2300mg sodium/day was associated with a higher risk of death from cardiovascular disease.

So what's all this hype about? Well, to put it simply salt metabolism, intake, excretion, physiology are extremely complex. They get even more complex in disease states such as hypertension and heart disease so prescribing bold cut-off points for what is arguably the most important mineral in the body will simply not work for everyone. What has not helped is that over decades the threshold of who is hypertensive has lowered making many 'normal' people now either patients or potential patients. There is no doubt that reducing salt will reduce blood pressure slightly BUT if you collate all the evidence as was done during a meta-analysis of 58 trials by Graudal in 1998, the conclusion is that the clinical benefit is so weak that the authors state the 'results do not support a general recommendation to reduce sodium intake'. It is generally agreed reduction of salt intake can be used as supplementary treatment but if you examine the literature closely the reduction by lowering salt intake is not more than can be acheived by eating a high omega-3 fatty acid diet or weight reduction or in fact relaxation therapy.

So my take on the matter.......! Eat sensibly and eat enough salt - not too much and certainly not too little, especially if ou are an athlete and sweating a lot. Avoid PROCESSED food that contain far too much salt- you'll be horrified to see how mcuh a can of tomato soup or even a slice of bread contains. REPLACE what you lose when exercising using an electrolyte drink matched to your rate of loss. Your sodium losses will predominantly be via sweat, as little as 100 ml/24 hr in normal weather, 20 degree C and no exercise and as much as 5000ml/24hr in warm weather, 29 degree C with exercise in the same person. Research shows that human sweat sodium losses vary as much as 10-fold in humans. So figure out how much sodium you lose and simply REPLACE it like for like.

Dr Raj Jutley
Chief Medical Office

Here’s what we have to say! …

Tuesday, December 20, 2022

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