How does knowing your sweat sodium concentration help with a nutrition strategy?
In this latest article, coach Philip explains why knowing your sodium loss from sweat is critical for endurance athletes. Read on to find out why sodium losses should be measured if you are doing a race that needs a nutrition strategy.
For most endurance events, there are three considerations that athletes must have when putting together a fuelling strategy. What needs do they have for
Fuel
Hydration
Electrolyte requirement.
Fuel
Fuel, for most people, is trainable and something that can be managed and learned. It will depend on the intensity, duration and the individual, but for the most part, people will be operating using around 60g of carbohydrates per hour; you can push it up to 90g or more using different types of carbohydrates and training, and it may be a little less if your race intensity is lower or shorter races, where fuelling is less important. This is not to trivialise an immensely complex field. However, the guidelines are reasonably consistent from person to person and well documented. It is all about trying what works for you (brand and dose) and becoming efficient at taking it on when exercising.
Hydration
Hydration needs will change a lot more depending on the environment. Hotter days, higher altitudes and more humid environments will change any individual's hydration needs. Each person sweats in different amounts and will respond differently to the conditions. Nevertheless, athletes can adapt to these changes and adjust their plans accordingly. It is also relatively straightforward to measure these changes objectively. Athletes can weigh themselves before and after exercise to determine how much weight change they have experienced due to sweat loss. This figure can be used as a basis to work from. Say you know you sweat 1L per hour; if you go somewhere hotter, you may use that as a reminder to drink more than that if you can. Equally, you may reduce that intake if you are operating in less sweaty conditions. Knowing your sweat rate is vital for any nutrition strategy, though, and gives you a starting point.
Electrolyte requirements
However, sodium losses through sweat can vary significantly between individuals. Currently, the range is between 200mg of sodium lost per litre to over 2,000mg of sodium lost per litre of sweat, with an average of around 950mg/L. This tenfold difference between individuals is staggering and can be compounded by how much someone sweats. For example, someone who sweats 1L/hr but only has 300mg of sodium loss will lose almost the same amount of sweat as someone who sweats 350ml/hour but has an average sodium loss (about 950mg/L). The two hydration strategies would be vastly different. If they were to follow “general” guidelines, one could end up with too little fluid or salts and the other with too much. The less salty sweat may think electrolytes are less critical, but their higher sweat rates mean the absolute amount of salt loss is high enough to make a performance difference.
This difference can cause real issues for athletes trying to get the suitable nutrition right, and these differences between athletes can cause many of the fuelling issues we hear about.
Why is sodium important?
Sodium is essential in the body for several reasons, but the main ones are:
Maintenance of fluid balance which means maintaining blood volume and regulating hydration
Cellular function
Nerve function,
Muscle contractions
Cognitive function
Importantly, we cannot create salt, as it isn’t made in the body; we need to consume it. If athletes are low on sodium levels, they can end up with hyponatremia. This condition has potentially severe consequences, including losing consciousness and death.
Aside from the health consequences, there is also a loss in performance. there isn’t yet an understanding of what the absolute limit of sodium loss is before performance is impaired. Beyond a certain point, performance drops. For example, blood volume will decrease if hydration is not maintained (when not maximised with fluid), and the cardiovascular system must work harder, or the output must be reduced. All we can currently work towards is reducing their losses and linking them to how much fluids they can lose.
How much sodium do you need?
Given the vast variance of sodium losses, guidelines could significantly change the sodium needs of each athlete. If an athlete was to follow average guidelines or what their friends do. As we saw, there could be a significant gap between what they need and what they have taken on.
Too much or too little sodium will result in underperformance at best, GI discomfort or even worse. Therefore, knowing your actual sodium amount is critical to creating your sodium levels. You can estimate these by guessing if you are a salty or less salty sweater - those who frequently cramp, have salt rings on their clothing, and crave saltier foods are likely to have a greater sodium concentration in their sweat. Otherwise, the gold standard is getting their sweat analysed, which we can also do at Tri Training Harder.
What do you do with this knowledge?
Once you know your sodium loss (ideally through actual testing), you can estimate how much you will lose based on your sweat rates, the environmental conditions and the duration of your event and then ensure you consume enough sodium or enough sodium based on how much you are sweating to mitigate any losses.
You may then use your hydration strategy to inform your fuelling strategy. For example, how much fuel will you take on through your drink? How much extra may you take with other fuel sources like gels or bars? Do these all combined provide you with enough sodium, fluid and energy for the event in question?
If we take the two athletes above with the different sweat and sodium losses. The first athlete, losing 1L/hr, may well be able to consume 90g of CHO through a drink-only strategy with a light sodium supplement. However, the person losing only 350ml of sweat an hour will struggle to get the fuel in with a drink-only strategy and must adjust their plan to allow for solid foods. On the other hand, with two 750ml bottles with the right amount of sodium in them, they could race for about 4.5 hours on the bike without needing more fluid!
All this helps you create an excellent, personalised fuelling strategy based on your known losses without estimating it or following guidelines that are more likely to be inappropriate for you than they are to work for you!
If you want to get your sweat analysed, then you can do so through Tri Training Harder. Use this link to book an appointment.
Philip is the founder of Tri Training Harder LLP. He’s a British Triathlon Level 3 coach, and has been coaching for over a decade and is involved with mentoring and developing other coaches.
Philip has have coached athletes to European and World AG wins, elite racing, many Kona qualifications, IRONMAN podiums and AG wins.
Alongside the conventional development through many CPD courses, he has also been fortunate enough to work alongside experts in the fields of Physiotherapy, Strength and Conditioning, Nutrition, Psychology, Biomechanics, Sports Medicine. Putting this knowledge into practice he has worked with thousands of athletes to various degrees, from training camps in Portugal and around Europe, clinics in the UK and online coaching.
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