Drinking while running
Chapter 6 explained the basic dietary requirements to support a healthy and active lifestyle. This chapter is about how you should eat and drink before, during and after running, and discusses the practicalities of doing so.
In general, you need to drink water and consume carbohydrates while running during runs that are longer than one hour or 10km. For shorter runs, you are unlikely to need to eat or drink, unless it is very hot in which case you may need water to prevent dehydration.
Dehydration and over-hydration
As we saw in Chapter 6, you need to consume about 1 litre of water for every 1,000 kcal you consume during the day. But in addition, you lose water through sweating when you exercise. A good rule of thumb is that you lose around half a litre for each hour that you exercise – and it can be substantially more than this if it is a hot day.
Some evidence shows that modest levels of dehydration lead to significant falls in athletic performance.[i] Your blood is about 82% water. As you sweat more, your volume of blood is reduced, and your cardiovascular system works less efficiently at getting oxygen to your muscles. A loss of water equal to 2% of your body weight (a litre and a half for a 75kg person) could reduce your aerobic capacity by up to 20%.[ii] Bigger sweat losses than this can lead to dangerous dehydration.
Contrary to the popular saying that “women glow, men perspire and horses sweat”, women also sweat while exercising, broadly the same amount as men (in proportion to bodyweight). So women should, like men, aim to replace the water they lose while exercising, either during the event (for longer events) or immediately afterwards.
In deciding how much to drink while exercising, however, you should take account of the fact that water is a by-product of burning fuel to produce energy. This means that your body is producing extra water internally when you are exercising, and you therefore don’t need to drink to replace all the water you are losing through sweat.
It is less well known that it is quite common, and quite dangerous, to drink too much water, especially during endurance events. In one study of 17 runners who were hospitalised during the Comrades Marathon (an 89km ultra-marathon in South Africa), 9 had hyponatraemia (this is low blood sodium, associated with over-hydration).[iii] At least two marathon runners in the USA have died of hyponatraemia. The risks of drinking too much water are at least as significant as the risks of drinking too little.
In a comprehensive discussion of this issue Tim Noakes concludes that distance runners should drink as they feel (and not force themselves to drink more), which generally means about 500ml an hour.[iv] However, other medical advice still recommends drinking rather more than this. For example, the American College of Sports Medicine recommends 600ml to 1,200ml of sports drink an hour.[v] There is a significant danger that this may be too much for non-elite athletes who are running a marathon which takes them more than four or five hours. You will have to judge for yourself what works best for you, recognising that there are dangers from over-hydration which are at least as great as the dangers of dehydration.
For running events of up to 10km, it is unlikely that you will need to drink during the run unless the weather is exceptionally hot. For longer events, including the marathon, your performance may suffer as a result of dehydration if you don’t replace the water you are losing during the race. But people running for more than four hours should also be careful not to drink too much.
Drinking before you run
One way to minimise dehydration is to ensure that you begin a long run fully hydrated. In the days before a big race, it is a good idea to sip as much water as you can to keep your body topped up.
On the day of the run, drink up to two hours before the start. Most experienced runners stop then, to avoid the need to urinate while they are running.
You can begin drinking again immediately before the start. Marathon running writer Hal Higdon recommends drinking a can of Coke on the start line of a race.[vi] Although this is a diuretic, it is unlikely to affect you during the race, and the caffeine jolt may help your performance.
Drinking while running
Drinking while running is a skill, and you need to practise it during your training to work out what works best for you. Some tips are:
- drink little and often to avoid a bloated feeling while you are running;
- drink as you feel inclined, which should be about 500ml every hour or a little more; if you are running a marathon and aim to complete it in four hours, this means about half of a paper cup of water every mile; but don’t force yourself to drink too much;
Organised races over 5km will usually provide water stations. Using these effectively is a skill that needs some practice:
- learn to take the cup from the helpers with your left hand; the water stations on the left side of the road tend to be less crowded than the water stations on the right;
- run on past the water station before you actually drink from the cup; you need to concentrate while you are running through the water station because runners will be weaving around and stopping suddenly in front of you, and there will be cups on the road which can be hazardous;
- take time to walk for a few steps to enable you to drink comfortably and avoid choking;
- practise drinking from cups during your training; the best way to do this is to enter one or two local races for training runs.
On a hot day, you should regulate your temperature by splashing water over yourself as well as by drinking. You may want to pour a cup of water over your head (and especially down the back of your neck), and if you are wearing a cap, make it wet to keep you cool. During the closing stages of a race – for example, during the last half an hour – cooling yourself this way may be more effective than drinking. It is also less likely to make you feel nauseus.
Drinking after running
When you have finished running, you should aim to replenish the fluid you have lost. Because you don’t absorb all the fluid you drink, it is recommended that you drink about half as much again as the volume of fluid you have lost.[vii] After a long run, you should try to drink at least 500ml immediately, and then the rest in slower time.
You should want to urinate within 6 hours of completing a long run. If you cannot, it is possible that you have developed kidney failure. If you have not urinated within 8 hours of finishing a long run, contact a doctor. If you are developing kidney failure, the earlier you get medical help the better.[viii]
[i] Fallowfield, J.L., Williams, C., Booth, J., Choo, B.H. and Growns, S., ”Effect of water ingestion on endurance capacity during prolonged running” , Journal of Sports Sciences , 14 , April 1996, pp 497-502.
[ii] National Athletic Trainers’ Association Position Statement: Fluid Replacement for Athletes, Journal of Athletic Training 2000;35(2):212–224. See http://www.nata.org/
[iii] Noakes, T.D., Goodwin, N., Rayner, B.L., Brankin, T., Taylor, R.K.N. (1985) ‘Water intoxication: a possible complication of endurance exercise’ Medicine and Science in Sports and Exercise, 17, p 370-375
[iv] Tim Noakes, ‘The Lore of Running’, Oxford University Press, 2001, pp265 – 273.
[v] reproduced at: http://sportsmedicine.about.com/library/bl_acsm_fluid.htm
[vi] Hal Higdon, Marathon: the Ultimate Training Guide, Rodale Press, 1999
[vii] Shirreffs, S. M., et al (1996), ‘Post exercise rehydration in man: effects of volume consumed and drink sodium content’, Med. Sci. Sport Ex., vol 28.
[viii] Tim Noakes, ‘The Lore of Running’, Oxford University Press, 2001, p835.