If the body was a closed system we’d be able to survive on just the water we’re born with, unfortunately it isn’t. Moisture is lost through sweating, breathing and execration. Much of this moisture is drawn from the between the spaces between the cells (interstitial spaces), which is restored by blood plasma. If the intake of water drops below the outtake, blood volume will decrease as this plasma is used up, which will effect your ability to perform. Less blood returning to your heart means it must pump faster in order to maintain the same cardiac pressure. The decreases oxygen flow to your muscles and a reduction in the removal of Carbon Dioxide and Lactic acid, causing muscle cramps and increasing muscle fatigue, as they are unable to recover effectively. In cold conditions the reduction in circulation can also lead to cold extremities, and is a big factor in frostbite, with the cold itself also compounding dehydration due to moisture loose caused in heating up cold air while breathing (up to 1.5 L an hour). It only takes a loss of three percent of your body weight in water to seriously impair your performance and skill levels, power, coordination, fine motor skills, endurance and ability to think clearly – a dangerous state to be in the mountains. If you keep sweating (don’t slow up, hydrate or get out of the sun) your sweating mechanism will begin to shut down causing your temperature to rise leading to heat exhaustion and eventual heat stroke (Body temp between 41-43º C).
How long does it take to sweat 3% of your body weight? Well an average non active body will loose 0.7 L of sweat a day, but an active person can loose up to 2.5 L per hour (1 litre weights 1kg remember), so you can see it doesn’t take long for dehydration to really curtail your performance. Many dehydration symptoms are also classic ‘altitude’ symptoms – pointing to the fact that good hydration should be taken as seriously as acclimation, as it may in fact be a bigger factor in your well being (i.e. That’s why Doug Scott always stops and has afternoon tea).
HOW MUCH SHOULD YOU DRINK?
Most climbers carry a maximum of 1 litre of fluid (one Nalgen or Sigg bottle), with only those who take hydration seriously taking more (usually climbers who are also bikers, runners etc), but before saying how much you should carry lets look at how you much you should aim to be drinking. Firstly you should not drink any more then your stomach can handle, which is about 150/300ml every 15 minutes (one mouth full of water is about 30ml). If you drink too much you will actually cause more harm then good (hyponatremia), but the right amount depends on several factors so you should experiment with what you comfortable maximum is without having water sloshing around in your stomach (you don’t want to end up like Anthony Andrews!). This gives you a minimum figure of roughly 600 ml an hour, so even if you double your typical water supply you’ll still be caught short.
GETTING IT RIGHT
Firstly you’ve not got to be short sighted about the importance of water – you need to except that carrying a few more kilos of water will not slow you down but speed you up, it will also keep you warmer and more aware. Hear are my liquid tips: -
• Drink adequate fluids the day before your climb, eating food with a high liquid content as well as staying off the beers (or offsetting the beer with plenty of water). Food with a high salt content can also promote better hydration the following day.
• Try and drink .5 L of fluid 2 h before exercising in order to promote adequate hydration and allow time for excretion of excess ingested water.
• One the hill the amount you take depends on the available water supply. If you’re near usable water supplies then you need only take a small bottle or bladder. If you’re in an alpine or winter environment you’ll need to take you’re own water, or melt water on the way. If we round things off and say we need a minimum of .5 L an hour (less then is recommended but it’s a start) then we still need aim to carry 6 litres of water for a short 12 hour day (most alpine and winter days will be more like 17 hours or more). This is not really feasible so balance must be struck. If you go faster with less water you can use that time to stop and melt snow at a brew break – or if you take more, you go slower but then you save on the brew stop! A canister of gas is lighter then several litres of water but that’s all it takes to produce that water out of snow, but melting several litres of water could take an hour. The good thing about water is that it gets lighter and light (plus you can just pour it away or drink more to lighten your load), you can’t do this with a stove and fuel. So a good compromise is to lower intake to a carryable level, aiming to maybe have a higher consumption on the way in when you are less tired, then switching to a low intake when you begin to slow (and so you body uses up less water). On top of this take a small pan and gas stove so you have the ability to stop and brew up if you run out of water.
• So what do you take? Well firstly use a bladder system, this will give you a drip feet that will match your water loss, and avoid overloading your system. Set out hydrated with a 2x 2 litre bladders aiming to drink the first bladder in the first 2 to 4 hours. Then swap over to the other bladder for the remainder of the day – maybe having a rest and a brew stop at lunch in order to lighten your gas bottle and top off your supplies.
• It’s best if the liquid is luke warm, so if it’s cold, try and have your bladder at 15?C, and your secondary bladder hot and insulated so it won’t freeze before you need it. Also add carbohydrates and electrolytes to your water as they help your performance (no more then 30-60 grams/hour).
• Be aware of taking food that requires a lot of water to digest, perhaps going for a sandwich over a water sapping powerbar.
• Once on the Hill don’t wait until your body is already suffering from dehydration you starting sipping. The rule is drink before you get thirsty - when you get thirsty - and in between.