Hydration Strategies for Ultrarunners
It is only in the last 30 years that serious consideration has been given to how much fluid a runner needs to hydrate for an ultramarathon. Before that time, most people who ran marathons and ultramarathons were elite runners who would usually finish a marathon around the 3 hour mark and so were not in need of a prolonged strategy to avert dehydration.
Today’s endurance athletes cover a wider range of ability and engage in triathlons, biathlons, duathlons,
adventure and multisport activities placing intense demands on their bodies. These athletes are presented with an arsenal of products designed to squeeze out the last drop of our potential by using hydration solutions that look good, taste good, are easy to ingest and easy to carry and actually do the job.
Before a runner actually gets to the starting line however, a good percentage of the job can and should be done. Training is also concerned with preparing the body’s nutritional and hydration requirements in the days leading up to the target event and a strategy of gradually increasing liquid intake in a steady and controlled way until full hydration is reached – ideally the night before a race.
So, for the beginner where does one start?
It has been recommended for several years now that we drink at least 8 glasses of water daily, however Heinz Valtin, a retired professor of physiology from Dartmouth Medical School who specialized in kidney research thinks that this amount is not necessary. He suggests that thirst should be our guide.
This is only really useful though if we have immediate access to water. Ultrarunning requires a deeper knowledge of the state of our hydration level to prevent problems of too little or too much water. Carrying hydrant on longer runs and ensuring regular supplies is of paramount importance.
However there is no absolute amount as this depends on many idiosyncratic factors. Guidelines to establish a hydrated state suggest that regular consumption of relatively small quantities throughout the day which result in the occasional passing of clear to lightly coloured urine will indicate a generally acceptable level of hydration. Darker coloured urine generally indicates a dehydrated state, though again this will depend on the type of diet being followed.
Learning what a fully hydrated system feels like can be facilitated by measuring body weight before and after longer runs. Most of the weight lost during a run is due to sweat loss. In hotter temperatures and or drier climates greater sweat rates should indicate that water consumption should increase proportionately.
It’s difficult and not really practicable to measure our body weight loss when we are out running but figuring out our sweat rates, at least a rough estimate, will help our overall strategy in maintaining an approximate equilibrium. Measuring body weight before and after an hour long run will give some idea of how much fluid we lose and by observing how much we drink to satisfy that depletion over a series of such runs will provide a baseline from which we can adjust our strategy to apply to longer runs.
Trial and error is a great way to learn although a slower approach. Observation will show us what we are actually doing. For example for a regular run of an hours duration take 500ml of water every time you go and drink as you feel thirsty. Over a week or so you will see that you usually drink about the same amount of water in respect of the conditions ie. if it is hotter you will drink more and less if it is cooler or raining. It will vary more or less but overall you will narrow down the unknown into an amount you can cater to. It’s best to err on the side of caution especially if the run is 3-4 hours and beyond without access to regular supplies.
Water absorbtion rates are also affected by our diet and as well as replenishing water levels, electrolytes are also esssential in helping to absorb that water.
What are electrolytes?
An electrolyte is any substance containing free ions that behaves as an electrically conductive medium – in the body this means an ionically charged salt. These salts help maintain essential cellular electrical activity and as they are used up, they need to be replaced.
The main electrolytes found in the body are :
• sodium (Na+)
• potassium (K+)
• chloride (Cl-)
• calcium (Ca2+)
• magnesium (Mg2+)
• bicarbonate (HCO3-)
• phosphate (PO42-)
• sulfate (SO42-)
When the electrolyte supply is depleted, all muscular activity is impaired accordingly. Without the electrical switching enabled by electrolytes water cannot be absorbed through the stomach and we experience a sensation of “sloshing” and heaviness in the stomach.
Electrolytes are added to sports drinks along with sugar and flavours and the electrolytes that need replacing the most are potassium and sodium. Various forms of electrolyte products are available including Endurolytes, Succeed S! Caps and Saltstick and Nuun.
How much water do I need to drink to be completely hydrated?
Hammer Nutrition recommend:
• Fluids: 20-25 ounces hourly
• Sodium chloride (salt): 300-600 mg hourly
However, these are just reference points for you to begin your experimenting to determine what your own body needs under a given set of circumstances and there are variables which should be taken into account which will affect the quantity necessary:
- Pre-event loading strategy
- Duration of event
- Intensity of effort
- Weather conditions
It is well documented how the body hits the wall for most people around miles 17-22 in a marathon. The body uses up what it has readily available and then after that, if we have not prepared ourselves to meet this stage of energy production then the body is placing demands on itself it cannot meet. Either we have to replenish stocks or reduce energy expenditure to a level that can be maintained. Replenishment takes time. Even gels will take some time to be absorbed into the energy production system and reach the places where demand is high.
The way around this then is to maintain a steady fuel intake that will ensure a gradual flow of nutrients and energy to the cells. In an ultramarathon this steady flow is essential not only to completing the event but to aid recovery afterwards.
I have heard of a few people who drink very little and who consume very few calories. I feel that their bodies have learned how to function very efficiently and that people in this category are very few indeed. In a multiday race getting a continuous flow of nutrients is as necessary as is water and oxygen. Without these three things only gods and saints are going to make progress.
My Multiday Experience
In the Self-Transcendence 3100 mile race in New York which takes place from mid June to the first week of August and includes some of the hottest and most humid periods of the summer, we have an aid station on the .544 mile loop that traverses Thomas Jefferson high school. The loop is partly shaded throughout the day with the least amount of shade being when the sun is at its zenith. Sunrise is about 6 and sunset is about 8 so 12-2 is the most intense time.
The aid station supplies water in small cups, about 3-4 ozs per cup and I like to take one of these every lap or every other lap depending on the temperatures, humidity and wind conditions, my daily lap target is 111.
Input is not measured solely against output but against thirst, sweat rates and urination rates and these can and do fluctuate. However once this becomes stabilised, after a few days, it’s easier to adjust drinking rates to allow a more normal urination frequency while absorbing high volumes of liquid.
During the hottest and most humid periods I can be drinking up to 40-50 ounces of liquid an hour. This usually involves an electrolyte drink, cola and water.
It’s hard to eat while consuming all this water as the digestive acids are diluted but important to maintain as no nutrients in = no energy out. It doesn’t take long for the reality of this equation to hit home.
Liquid meals are useful, protein shakes with a break from taking in hydrant for a lap or two but this has to be very carefully monitored in extreme conditions as the bodies tolerance ranges are narrowed and too long without food or hydrant will have a big impact on energy production and hence performance.
Ultrarunning and multiday running requires a steady flow of hydrant and nutrients. Personal experimentation will establish a baseline for the required quantities to maintain this flow and this is part of training for ultramarathons. A reasonable starting point is 20-25 oz/hour. Monitor the bodily functions and develop a feel for what’s necessary under different conditions. Support hydration with necessary nutrients and maintain even after the event is over to enable the recovery process to begin optimally.
Karl King, President of Succeed, has produced a table featured in Ultrarunning magazine in May 2007 that lists the conditions of dehydration, over-hydration, hyponatraemia, hypernatraemia and combinations of each with symptoms normally associated with each state. It is worth having a look at this summary.