Fortunately sports science has come a long way since 1909 and we now know that regularly taking water and fluids during exercise and competition is essential. The bad news is that dehydration or hypohydration impairs the body’s ability to regulate heat which will result in an increased body temperature and an elevated heart rate. Also, mental function is reduced having implications for concentration, decision making and motor control and all these effects will have downside to performance. The good news is that drinking regularly during exercise will eliminate the adverse effects of dehydration.
The problem is that fluid requirements vary considerably between athletes and fluid losses are affected by fitness, when fitter runners will sweat earlier and in larger volumes, body size, when larger runners tend to sweat more than smaller and of course genetics when some people innately sweat more than others. It really is impossible to formulate a fluid replacement plan to meet all needs, however you can estimate your own fluid requirements with two options. Firstly, drink according to your thirst, that is, drink when you feel you’re thirsty or, and this gets technical, weigh yourself before and after a run or training session. Each kilo of weight lost is approximately equal to one litre of fluid, so add on the weight of fluid that you have taken on during the session, and this will provide you with an estimate of weight loss by weighing yourself after the session. So, for example, if you finish a run half a kilo lighter than when you started, having taken on 500ml during the run, your total fluid loss will be one litre. Remember though that you must expect to lose weight during a run, particularly when you’re out for over an hour and remember too that you don’t have to glug fluids after your run to replenish lost fluids – do it gradually.
Of course, we are not helped by the bottled water companies who claim, that a two per cent reduction in body weight will result in an up to ten per cent reduction in performance. These figures come from various studies that have been carried out by universities in their research laboratories and of course sponsored by the bottled water companies. By believing the marketing hype, we are being encouraged to drink and buy more bottles of water. Double blind clinical trials do not show the same results as the sponsored studies, how surprising is this? Loosing two per cent body weight certainly did not affect Haele Gebrselassie when he won the Berlin Marathons in 2007 and 2008, both in world record times, 2:03:59 in 2008 – he actually lost ten per cent of his body weight on both occasions.
There is also another side of dehydration. Let us consider for a moment the African bushman in his pursuit of an antelope. The hunt will start at a slow walk-trot, while a full blazing equatorial sun beats down on both man and beast. Before long, the bushman’s forehead and chest are covered with sweat, but he still presses on. No drinks stations every 5K for him. The chase will go on for many miles, this is really hot arduous stuff, a life or death pursuit, Eventually, the bushman seizes the moment, breaks into a sprint and buries his spear into the antelope. And then of course the antelope has to be taken back to the bushman’s village. It really makes no sense that we have evolved over time without the ability to continue exercising while dehydrated.
There is also the opposite of dehydration and that is consuming too much fluid, resulting in a condition known as hyponatraemia, low blood sodium levels, basically caused when over-hydration while exercising dilutes the sodium in your body. The possible result, in the most serious of cases is brain swelling that can lead to seizures and other life threatening complications, the longest lasting one being death. This makes hyponatraemia the most important marathon related health risk facing runners everywhere. Indeed, in the 2002 Boston Marathon, it is believed that over thirteen per cent of the field had suffered from hyponatraemia. In the 2007 London Marathon, a 23 year old fitness instructor died from it.
As runners we must also consider energy drinks, but those such as Red Bull, are totally different from using a specially formulated isotonic sports drink. We should really understand the difference as the isotonic sports drink will greatly help to replace the nutrients and fluids that we have lost through our exercising and running. Whist an energy drink will give you a quick and short lasting boost to your energy levels as they are full of protein, as a pre-run drink they can adversely affect your run as they will increase your heart rate. Not only that, they contain loads of sugar with the consequence of reduced blood flow.
So, let’s put this all together, you’re going to be running a marathon, you have two options, drink according to your thirst or, drink only to the point at which you’re maintaining your body weight, but not gaining weight, and think about these:
- Don’t overdo it in the days before your marathon, drink when thirsty, but make sure you drink about 250ml of water no less than half an hour before the start.
- Don’t take non-steroidal anti-inflammatory drugs such as aspirin or ibuprofen, before, during or immediately after the race.
- Weigh yourself before the marathon and write your weight on the back of your race number. If you need help at the finish line, the marathon medical staff will find this pre-race weight helpful should they have to attend to you.
- During the marathon, drink when you’re thirsty, understanding that water, sugars and electrolytes will help you feel and perform your best, but don’t force yourself to drink.
- Don’t tip water over your head, thinking it will cool you down. It won’t, as it will fool the brain into thinking that you’re cold and it will respond by heating up your body. Splash it over your shoulders instead.
- Be particularly careful if you expect to run for more than four hours, and if you have an unusually small or large body. Drink less if you have a queasy, sloshy feeling in your stomach.
- Sports drinks are better than water, but they won’t stop hyponatraemia. Always try out the sports drinks in training as they might disagree with your digestive system.
- Don’t glug fluids immediately after the marathon. Nibble on solid foods and sip a variety of drinks slowly, particularly milk, until you feel recovered.
So, we know how and when to drink water and hydrate when we’re exercising or running a marathon, but what sort of water do we actually drink, should it be bottled or tap water? Unfortunately, when we’re in a race, it’s likely that we will be drinking bottled water from the water stations, but when we’re in other situations going about our day to day lives, we do actually have a choice and ideally this should be tap water, filtered and in a stainless steel re-usable bottle. Bottled water companies, unlike the municipal water utilities are not required by law to disclose how their water is actually treated or filtered or indeed, to provide any information as to the source of their water on the bottles, so that bottled water is not strictly regulated. There are one or two companies that advertise with images of mountain streams and one particular that tells us that their water has been cascading down the mountain for one hundred years. Unfortunately the game is given away as there is a sell-by date on the bottom of the bottle. In fact, in most cases, the water that they package is usually filtered tap water from a city water utility and described as coming from a municipal water source.
Another factor is that bottled water can cost many times more than it would cost you to filter your own water from the tap at home. However, putting it in a plastic bottle generates plastic pollution and it’s likely that about six out of ten plastic bottles are not re-cycled. It is also said that if all the plastic water bottles discarded in the US every week were lined up, they would go round the planet five times so just think of all the barrels of oil that would be needed to produce those bottles.
So, why should you use a stainless steel bottle? If we look at the alternatives , plastic re-usable bottles and containers can contain chemicals such bisphenol A, a synthetic oestrogen or its alternative bisphenol S, both of which have been linked to hormone disruption. PET, or polyethylene terephthalate, plastic water bottles which have the re-cycle code 1, may contain chemical additives that may leach into the water. And then of course there’s aluminium water bottles but these are often lined with epoxy lacquer that contains BPA, bisphenp-A.
Go for stainless steel every time although not all stainless steel bottles are created equal. Go for 100% food grade stainless steel interior, make certain there is no plastic lining inside the bottle or plastic on the cap. These things are clearly labelled - read those labels carefully - if they’re not, don’t use them. Best quality comes from health food stores where owners are far better informed than employees from high end stores.
Just one final thing, if there are two of you drinking water, never say ‘cheers’, it’s bad luck.