How to stay hydrated during the Back Country Cuisine Alps2Ocean Ultra

By Andy Blow | 10 Minute Read

Alongside pacing, foot care and energy intake, hydration is one of the most important factors behind success at the Alps2Ocean Ultra. When you’re running over 300km in 7 days through some of the most epic trail in New Zealand, staying hydrated is going to be critical.

Luckily, it’s something you can get ahead of before you arrive at the start line, 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.

But hydration for ultra running not just a case of drinking plenty of water. In fact, just drinking water alone could ruin your race. That’s why your race directors have asked us to supply our blister-packed SweatSalt capsules to help you stay properly hydrated during your race and these will be available on the course each day. But before we get on to how to make use of those, let’s take a step back and ask…


Why is hydration so important?

Well, 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 conditions, where heat dissipation is more difficult and fluid loss dramatically increases.


 The Alps2Ocean trails are beautiful but it can be hot!


How worried should I be about being dehydrated during the Alps2Ocean?

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 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 your performance. So keep in mind that just because water is available at the checkpoints each day, this doesn’t mean you have to drink as much as you can. 

But, how much is enough? It’s reassuring to remember that you have a pretty powerful, innate ally in the fight against dehydration; your thirst instincts. 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 you’re training (if you train in cooler climates), 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, it's been receiving more and more press coverage in the last few years. The word literally means “low (‘hypo’) blood sodium (‘natremia’)” and it 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 and 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.

Taking in adequate sodium along with the fluids you consume is helpful for maintaining levels in your blood stream, that's why you'll be issued with our SweatSalt capsules during the race.

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.


Why are electrolytes important?

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’s 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 your blood volume, which in turn helps with management of your core temperature and the delivery of blood to your working muscles and skin.

In fact, during this really interesting scientific study in 2015 researchers found that athletes taking salt capsules with fluids during a middle distance triathlon finished 26 minutes faster on average than a control group who took a placebo.

They put this dramatic performance effect down to the fact that the sodium enabled the athletes taking it to maintain their blood volume more effectively and therefore continue to perform at a faster pace for longer than the control group.

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 your 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 as much as 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 just doesn’t work.


So, how should you be drinking?

Once the Alps2Ocean Ultra gets going, the amount you’ll need to drink will largely be defined by how long you’re out there each day, how much your stomach and gut can process per hour and your sweat rate (which will in turn be driven by genetics, your work rate, clothing choice and ambient temperature).

All of these variables mean that everyone has different requirements in terms of how much fluid you need (and can) take on. That means copying what other athletes are doing is definitely not a good idea. Instead, spend some time now to figure out the kind of range of fluid intake that works for you in training and other smaller events to dial in on a strategy that’ll benefit you.

Once you settle into each stage, it’s a good idea to both listen to your body (i.e. to drink to the dictates of thirst to a degree, not forcing in fluid when you don’t feel you need it) whilst also putting into practice what you’ve learned in training. Bear in mind that you can’t afford to drink too little early on in each stage without dehydration becoming a potential issue several hours in.

Whilst everyone is different, as a general rule of thumb, most ultra runners end up needing something in the range of 500ml to 1000ml of water with hypotonic electrolyte drinks (or electrolyte capsules) per hour. So, that’s probably not a bad range within which to start your own experimentation in order to figure out what’ll work for you.


Do I need to drink electrolytes during the Alps2Ocean Ultra race?


What drinks should you be drinking and how does that impact how you fuel your race?

We’ve developed a simple, free online Ultra Running Sweat Test to help you work out what strength electrolyte drink is right for you.

As I mentioned, his varies considerably from athlete to athlete. The average athlete loses about 950mg of sodium per litre of sweat, but about 15% of athletes will be losing over 1,400mg/l and we regularly Sweat Test people who lose as little as 400mg/l. But, amazingly, typical electrolyte supplements usually only contain 200-550mg/l! This is why personalising your hydration strategy is so crucial.

The composition of what’s in your drink bottle will also make a huge difference to how well it hydrates you and how easily it’s absorbed from your gut into your bloodstream.

For a multi day event like the Alps 2 Ocean Ultra, a hypotonic drink (i.e. one containing little to no calories) is highly likely to outperform anything more calorific. That’s mainly because it’s way less likely to cause you stomach issues and sickness as the stage goes on as you’re satisfying your high requirement for fluids and electrolytes.

My main piece of advice is to look at what you’re putting in your bottles as fluids for hydration rather than a source of significant calories/fuelling. Aim to get most of your calories from solid foods, gels, bars, fruits and whatever else you’re carrying in your pockets or can pick up from the checkpoints en route. Again, we’ve covered this topic in another blog post if you want to read about it in more detail.

By taking this approach to fuelling and hydration you maximise your chances of keeping optimally hydrated whilst keeping your stomach happy and getting in enough energy to see you right to the end of the course, even in the most extreme conditions. 


How can maintain sodium levels during the Alps2Ocean?

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 your own hydration supplements or capsules with your water. The advantage of this 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.
  3. Taking the SweatSalt Capsules that are available on the Alps2Ocean course These contain 250mg of sodium per capsule and you can read more about them here. These will be a great backup but I’d generally advise that you test them out in training first and, if you’re carrying bottles with you, you should definitely consider carrying your own electrolyte supplements to mix in with your water. It’s always better to be reasonably self-reliant.



  • Managing hydration is going to be an important part of doing your best at the Alps2Ocean
  • Hydration for ultra running not just about drinking lots and lots of plain water though!
  • Balancing water and electrolyte (sodium) intake against your sweat losses is the most important factor to get right
  • Hydration and electrolyte intake are very individual and our free online Ultra Running Sweat Test give you an idea of the levels of intake that are likely to be right for you
  • Precision Hydration SweatSalt Capsules will be available on the Alps2Ocean course at checkpoints for you to use to manage your electrolyte intake during the event itself

If you decide you’d like to use our all-natural, multi-strength electrolytes or some SweatSalts to personalise your hydration strategy during your training over the next few months as you prepare for the event, just use the code A2O to get 15% off your first order.

Train hard and enjoy the race of a lifetime,

Andy Blow has a few top 10 Ironman and 70.3 finishes and an Xterra World Age Group title to his name. He has fond memories of racing the Coast to Coast event in New Zealand in 2012 too. He founded Precision Hydration to help athletes solve their hydration issues after learning about them the hard way himself! He has a degree in Sport and Exercise Science and was once the Team Sports Scientist for Benetton and Renault F1 teams.

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