by Uphill Athlete’s High Performance Dietitian Rebecca Dent
Hydration is key to every endurance endeavor, from mountain running to rock climbing. In their book Training for the New Alpinism, Steve and Scott advocated starting climbing days well hydrated, and carrying much less water than was considered normal at that time. Their sound advice has changed the way many mountaineers hydrate. The simple fact is that the weight of water often limits how much can be carried. And with access to fluids often limited at high altitude the problem is further exacerbated.
In this article I want to expand on Steve and Scott’s original advice and provide several hydration tips can help alleviate severe dehydration on any big mountain day whether it be training or racing.
First we need to establish that simply drinking to thirst when out on the mountain should be sufficient to offset any significant level of dehydration that would be detrimental to performance. However in situations where free access to fluids, to top up your water bottle, is limited or when urination breaks are undesirable, choosing a drink that has a greater energy and sodium content will promote longer term fluid retention.
Anecdotal reports from my work with mountaineers, have reported as little as 500ml of water per day having been consumed and usually a maximum of around 2l is carried at any one time, when out on the mountain. If you are able to drink to thirst with sufficient access to fluids, then drinking water will be sufficient. However during long days in the mountains, when you know perhaps you will not be able to access enough fluids to continue drinking to thirst, then considering your choice of beverage may in fact help aid the absorption of fluid, when compared to drinking water alone.
Detrimental effects of dehydration
Why is dehydration a problem? Dehydration when sufficiently severe will have an adverse effect on mood, as well as mental and physical performance. This can impair decision making, cause early fatigue and increase perceived effort, meaning the physical and mental tasks at hand just feel harder to do. All potentially compromising safety and enjoyment of the day.
It was attention to hydration that was cited to be one of the reasons contributing to the first successful attempt to summit Mount Everest.
Factors affecting fluid loss:
Individual sweat rates, level of fitness, physical exertion, direct sunlight, glare from the snow and layers of clothing will all effect how much fluid is lost from sweating.
At high altitude water loss is significantly increased due to the dry air and increased rate of ventilation to maintain tissue oxygenation.
It is important to get used to your own fluid requirements! Estimating your own fluid needs is best done through experience. Practice drinking to thirst or devise a hydration strategy during training / before you head out up high. Consider the environment you are heading in to, how long you will be out for and your access to fluids?
Best Fluid Choices:
The formulation of your drink will effect the rate at which the water content will be absorbed. The amount of fluid that you drink at once will also have an impact on how much fluid is absorbed. If a large volume is consumed at once, less will be retained.
The beverage hydration index study showed that drinks with a higher energy and sodium content help the body to retain more fluid compared to drinking water alone. This study demonstrated that the beverage hydration index for milk, orange juice, oral rehydration solution and full sugar coke was significantly higher 2 hours after ingestion compared to water. What this means is that the body retained more fluid after 2 hours, when drinks with a higher beverage hydration index were consumed compared to drinking the same volume of water.
If you know your fluid intake is going to be compromised on big days, these drinks with a higher beverage hydration index, could prove beneficial to offset significantly severe dehydration.
Try these practical tips…
- Consider the scenario you are entering, will you be able to drink to thirst or will you only be able to drink in opportune breaks?
- Get to used to your own fluid requirements, think about your past experience of hydration in the mountains and consider if this can be managed better?
- In the days leading to a high mountain trip aim to maintain hydration. This can be done easily by sipping regularly through out the day on fluids and monitoring urine output and color. Your urine should be a pale straw color.
- Start your mountain day hydrated. Give yourself a head start, once you set off dehydrated you are already on the back foot and increasing the likelihood of severe dehydration resulting in impaired physical and mental performance. Include a glass of milk, orange juice with your breakfast or having a milky coffee will help you to retain more fluid and reduce your need to go to the toilet before setting off.
- Drink to Thirst: Relying on thirst and your habitual drive to drink may be sufficient but at altitude having a planned hydration strategy could go along way to help offset severe dehydration e.g. take a mouthful of fluid in opportune breaks in the day, carry a drink that has a higher energy and sodium content and includes some sodium e.g. 200ml of fresh fruit juice add 300ml of water plus a pinch of salt. If you carry two soft flasks perhaps have one with water and fill one with a sports drink. Always practice prior to your main event!!
- Eat and drink water together: Whenever you eat something take a mouthful of water to wash it down. The energy and salt content of your food will help retain more of the water.
- When fluid supplies are low and you want to preserve water for the rest of the day, take a mouthful of fluid, swill around your mouth, then swallow (similar to using a mouth rinse after brushing your teeth). This sensation of fluid around the mouth can have a positive sensory effect.
- Rehydrate at the end of the day, particularly if you have a short time frame; Eat and drink together, drink a glass of milk, coke, recovery shake or hot chocolate immediately off the mountain. Have a glass of fruit juice or milk with your meal, sip regularly on water until approx. 30mins before bed time.
- If you feel extremely dehydrated off the mountain and have consumed only a small amount all day with only a short turn around of time until you are climbing again, consider taking a oral rehydration solution to drink.
- Hydration Systems: It is up to you which is preferred to be carried and used, what ever will encourage you to drink and is easy to carry is your best bet. Nalgene bottles and soft flasks tend to be the preferred choices.
To summarize: When access to fluids is going to be limited and rehydration time is short then consider making the most of the fluid you drink using the strategies outlined.
References and Further Reading:
- Benson et al (2015) Executive summary and conclusions from the European Hydration Institute expert conference on human hydration, health, and performance https://doi.org/10.1093/nutrit/nuv056
- Martin D. Hoffman, Trent Stellingwerff & Ricardo J.S. Costa (2018): Considerations for ultra-endurance activities: part 2 – hydration, Research in Sports Medicine, DOI: 10.1080/15438627.2018.1502189. https://doi.org/10.1080/15438627.2018.1502189
- Maughan et al (2016) A randomized trial to assess the potential of different beverages to affect hydration status: development of a beverage hydration index. https://academic.oup.com/ajcn/article/103/3/717/4564598