Caluculating fluid loss

[Deleted User]

I ran 10 miles this morning. Pre run I weighed 13st, 4lbs, 6oz. I drank 750ml fluid during the run.

Post run I weigh 13st 2lbs 4oz.

Anyone know how to calculate how much fluid I should have drunk over that distance?

Thanks.

[Deleted User]

I don't think you need to maintain your weight - without checking, I think Noakes 'Lore of Running' says something along those lines anyway. You'll lose mass by converting liver glycogen anyway, and that needs replacing by eating.

Personally, at this time of year I wouldn't drink anything, and I don't think nothing's too little.

For what it's worth, one litre of water (or sports drink, approximately) weighs exactly one kilogramme, and one kilogramme is 2.205 pounds.

[Deleted User]

I've looked into this a bit more and it seems that for copious 'sweaters' like myself that this is quite important.

This site: http://www.brianmac.demon.co.uk/drinks.htm
suggests that a 2% loss in bodyweight will impair performance, so I've taken 2% as the max weight I should 'want?' to lose.

I used this site:
http://www.allmeasures.com/conversion.asp to convert total weights into ounces.

I used Swerves value of 1 ltr fluid = 1Kg (= 35.27 ozs)

Pre run weight = 14,4,6 = 3206oz
2% loss = 14,0,5.8 = 3142oz
Actual post run weight = 14,2,4 = 3172oz

So, had I NOT added 750ml (35.27oz) of weight during the run, then my post run weight would have been 3137oz, which is below the 3142 target.

This weeks 10 mile run went okay (ignore bad knee and sore feet) and I drank 750ml water. Last weeks 9 mile run was 17 secs per mile slower (no big deal) but at the end I had bad shivers and I went back to bed and it took an age to get warm. I felt much healthier (non-flu'y) after this weeks run and I suspect that had I drunk 1 ltr of Lucazade instead of 750ml water I would have felt better again.

Or this might all be nonsense but it was fun building the spreadsheet anyway.

[Deleted User]

Oops, slight mis-calc, 750ml = 23.45oz, = 3145oz, just over minimum weight.

[Deleted User]

Pretty much all your weight loss during exercise will be due to fluid loss so you should look to roughly maintain body weight.
That means one litre per kilo lost. (Half kilo means half a litre etc)

[Deleted User]

Think time is a big factor here...but like swerve I run 14+ miles without fluids. But would always grab a drink somewhere if I was out for 2 hours or more.

cougie

I wouldn't bother drinking over that distance to be honest with you. Your body can easily cope with that amount of fluid loss - even for heavy sweaters. Just make sure you aren't dehydrated before you begin.