Clue to marathon success...

[TheReverand]

My head hurts, I think I need a drink....

[Updownupdown]

I wasn't doubting the validity of the research or their conclusions - more the reporting of them in the BBC article. From that article, I got the sense that they were advocating that you shouldn't drink anything and you will therefore run much faster, which is obviously not right.
Regarding my comment on the stats, if you look at Figure 1 in the paper, you see a lovely bell-shaped normal distribution. This is the same distribution you would see if you look at, for example, a statistical analysis for all the heights of the members on this forum, and possibly could be expected.
Figure 2 is the figure where I have the slight issue: the simple mantra of drink less, lose more body weight, run faster as advocated to a certain extent in the paper and strongly in the BBC article is not necessarily true. In fact if you look at the fastest runners in Figure 2, the top 5 were all in the range 0-5% loss, although one of these
could actually have gained weight. I'm also not 100% convinced on the validity of the fit in this figure. I could quite happily plot a straight line with negative correlation to that data and argue that it was valid, simply because of the clustering in the 0-5% BW loss. I would need to see more of the statistical methods they've used to come up with
the correlation to be completely convinced.

Well I take your point, drink less/run faster is potentially as much rubbish as the drink 500ml per hour nonsensical advice.
I've read quite a bit of Noakes opinions and research, he doesn't seem to advocate not drinking but more a drink when thirsty/maintain normal osmolality approach, which makes a certain amount of sense to me.

Yes, I don't doubt that journalists will misinterpret this just as they fouled up the fish oil "trials" and the MMR vaccine.

It would be interesting to hear the BJSM/Authors response to the stats queries.

Potassium? Just another reflection of dilution? Surely the dangerous thing is cerebral oedema, that's what actually kills people not low potassium, and that's more influenced by sodium- there's more of it basically, and you'll not kill someone with hypertonic saline IV.

[Mike T]

Are you referring to so called Normal saline - 0.9% - which is slightly hypertonic - that is, it is a bit more concentrated than normal blood - or 3% saline which can do horrible things to people if too much is given? I have read that 100mls of 3% is safe if given in a situation where acute hyponatremia is likely and a blood test would take too long though I cannot recall if there were any useful references. The best treatment for hyponatremia is of course prevention, by not drinking too much in the first place.

[Updownupdown]

Are you referring to so called Normal saline - 0.9% - which is slightly hypertonic - that is, it is a bit more concentrated than normal blood - or 3% saline which can do horrible things to people if too much is given? I have read that 100mls of 3% is safe if given in a situation where acute hyponatremia is likely and a blood test would take too long though I cannot recall if there were any useful references. The best treatment for hyponatremia is of course prevention, by not drinking too much in the first place.

100ml 3%, apparently defensible practice in an emergency as you say. Never had to give it though. I've heard of athletes ending up in ITU as a result of being given 0.9% in the mistaken belief that they were collapsed and dry, when they weren't.

We lugged an osmometer round one event so paranoid had I become about the issue after discussing scary experiences with the WHW race Dr.

These things are rare, but perhaps get less rare when looking after big fields of relatively inexperienced runners.

[Mike T]

http://www.westhighlandwayrace.org/R...al_advice.html

Thanks for reminding me - I have read this before but had forgotten about it. I must say it seems to be excellent advice and certainly fits in with my understanding of weight change and fluid requirements in long events in a relatively cool climate. Triathlons in Hawaii are of course a different matter, as are military scenarios where the duration/level of exertion/access to fluid/calories are all unknowns.