To drink or not to drink

[Brotherton Lad]

I did about 30 marathons fairly seriously down to 2:30. Most of the water I picked up went over my head or on to my legs, less than a pint made it to my stomach. Only on very hot days would I deliberately drink more.

[Rob Furness]

I don't have any idea whether I "need" to drink on longer runs (haven't done a marathon yet so can't comment there) but I do know I feel better and am able to refuel on the way round more comfortably if I do have some water. That said I did 19 miles this morning and took a 275ml bottle with me and only drank about a quarter to a third of it. I think sometimes it's more to do with comfort then actual need, but either way I won't be stopping to take any water on long runs as a result of some calculations.

Although I suspect this thread is more an attempt to wind up another forum member than a serious question

[Brotherton Lad]

When doing my long training runs on roads, I never took any water or food. I deliberately trained 'dry and empty'.

I've found with long fell running, though, that I do need to take food on board and for that I also need water. I'm not sure whether that's a function of fell running or my age and lack of training.

[Mike T]

Using glycogen both liberates water stored with it AND generates water when it is metabolised to CO2, H2O, and energy. Steady state exercise at very low levels like walking uses mainly fatty acids, but marathon like events completely deplete the slow twitch fibres and even some of the fast twitch ones of their glycogen stores (Noakes, Lore of Running, 3rd edition, pge 67) - so there is plenty of glycogen used to liberate/generate water. Even at only 30% VO2max, the main energy source is glycogen until after the 3 hour mark, when fat takes over (pge 76).
I am no great runner, and need all the help I can get in races - if those around me are willing to handicap themselves by carrying/consuming unnecessary water I suppose I should let them get on with it - but part of the joy of running is seeing others improve/succeed with fairly simple advice - such as an appropriate and scientific water strategy. I am not suggesting that everyone runs marathons without drinking, but as long as it is not hot it certainly works for me.

[shaunaneto]

Horses for courses, I sweat like a pig when fell running, whether it's hot, cold, mild, wet. If I don't drink water it all goes to pot very quickly.

[Mike T]

Some people sweat an amazing amount - at our local track are several who have water dripping off their noses after a few gentle warm up laps - and if you run behind them you get almost rained on. Each runner has to sensibly work out their water strategy, taking into account sweat rate/temperature/duration/access to water on the route and so on. Weigh yourself before and after a long run and work out your sweat rate, knowing that weight loss and dehydration are not the same thing. The only time I suffered from not drinking was on a 20 mile run on a hot day - high 20s - this was a deliberate experiment - I lost 7 lbs - just over 5% of my body weight - and was getting dizzy and slow towards the finish.