by Mark Wolff

In the lead up to Two Oceans Ultra Marathon myself and David Katz launched a series of podcasts discussing a few topics that all runners should focus on these being:

  1. Hydration
  2. Taper Week
  3. Race Day
  4. Fuelling
  5. Recovery

In this first part we focus on Hydration:

Hydration is probably one of the most critical aspects when it comes to a sport event, especially an ultra-marathon.

Below is a good read to understand what you should be thinking about around Hydration and you can also listen to the podcast I have pulled in below which I did with David Katz.

What Dehydrates You

A person should be completely hydrated leading up to an event and make sure that they’re in the 100% hydrated state when they start the event. You don’t want to be in a dehydrated state, so the first thing I suggest is to eliminate anything that would possibly dehydrate you.

We’re looking at things like diuretics, overdoing it with diuretics and not replenishing lost fluid. If we take a look at something like alcohol which acts like a diuretic, because it does also pull the fluid out of the muscle. It basically dehydrates you, so that should be completely cut out leading up to that event. Its serves no purpose and will only hamper your ability to remain hydrated properly.

Factor in the Temperature

As far as hydration goes during an event, there’s a few factors that need to be taken into account. The first is taking a look at temperature, humidity and individual sweat loss. An athlete should understand how much fluid they possibly would lose during an hour under certain circumstances or at what time of the day. This understanding comes through training and taking notice of fluid consumption and weight fluctuation before and after exercise due to fluid loss. So early in the morning, you sweat a little bit less and as the day gets hotter, you obviously have a higher sweat rate which means you are losing more fluid in the form of sweat with temperature increases.

Hot and humid climates also play a role in  exaggerating the sweat loss. Hydrating during and event is trying to replenish around 80% of the fluid lost during an event, that is what we aim for from a hydration point of view. As the day gets a little bit hotter, absorption is lowered a little bit and you would need to look at taking a drink with minerals to help further increase that absorption rate.

Possible Hydration Drinks

There are three types of possible hydration drinks one could possibly consume. Obviously there’s water in its purest form, which is a good form of hydration. However, the absorption rate of water on its own is not as high as water with a carbohydrate and a mineral solution. Then in that classification we look at two different types of drinks, one being isotonic and one being a hypotonic drink. A hypertonic drink is energy dense and hampers fluid absorption in favour of energy so we will leave that out as an option. Bare in mind though that if you consume gels or other means of energy products and don’t bring in a sufficient amount of fluid with that intake you will hamper fluid absorption which will lead to issues such as nausea and or cramping so do not overload on energy products.

An isotonic drink has an approximate balance between minerals required for hydration and carbohydrates which are required for energy. There’s very much a balanced pressure which is defined as measurement of osmolality. This occurs between the  digestive system and the blood from a pressure point of view and this balance allows a nice even pull through.

However, as heat goes up, you’re losing a lot more fluid and the body requires a higher rate of fluid absorption to replenish lost fluid in form of sweat. In this case you probably need to look at something like a hypotonic drink. In that case you’re looking at something like a 32Gi Hydrate (Click here to find out more about Hydrate), a mineral complex which will aid a higher rate of fluid absorption.

Try Mineral Loading

One of the things I do recommend is mineral loading and completely hydrating before an event, because it can delay the onset of excessive fluid loss and cramping later on in an event. Obviously you don’t want to be in that state.

I have spoken previously about overdoing hydration and that’s when you consume too much fluid. If you over consume and not being absorbed, what will actually happen is that you will feel a  sloshing effect in the stomach, I call this the ‘washing machine effect’.  At this stage you should stop drinking completely and wait for that fluid to be absorbed before you continue drinking. A salt tablet or mineral complex can help remove that fluid a lot quicker. In order to prevent over- hydration you should rather take smaller frequent sips of fluid over a period of time and not to wait too long to take in any fluid en route. Frequent small feed are best.

Race as you have Trained

In any event you participate in you need to race as you have trained. Do not make any changes on the day as far as hydration goes. You should be very familiar with what you require from a hydration point of view. Do not try anything new on race day.

I hope this helps clarifying hydration before and during your event. Stay tuned for the next blog and podcast covering the taper week leading to your race.

If you want a deeper dive into hydration check out my blog Simply Hydrate


all the best


Mark Wolff is an endurance, nutrition and physiology expert with over 20 years experience. An endurance multi-sport athlete with a triathlon, mountain biking and weight lifting background, he works extensively with professional and amateur athletes in a variety of sports disciplines as well as those just wanting to change their lifestyles. He firmly believes that a person can only reach their full potential when their health and nutrition is down packed. Mark’s focus on nutrition and physiology is not just on training and racing, but he places major emphasis on recovery, immune system health, emotional stability, stress management and performance. Mark is co-founder of 32Gi, a sports nutrition company, focused mainly on health and endurance nutrition. He is a certified sports nutrition expert as well as a marathon, track, triathlon and cycling coach. He spends most of his time guiding athletes with a very holistic approach to blending training and nutrition for performance and health


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