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Notes about hydration

Rob's picture

By Rob - Posted on 12 January 2010

This may or may not be of any interest to anyone, but...

Steve & I went on a little ride today and before leaving I joked to the GF I'd probably loose 4kg or so during that outing. Well, what do you know, that pretty much happened!

None of this is very accurate of course, because my memory sucks and our scales are not the best, but here's some figures all the same:

This morning, around 7:15am after eating breakie I weighed about 84kg.
When we'd done riding and sitting around talking cr@p Eye-wink (around 1:30pm) I weighed about 79.5kg.
I have been constantly drinking since then and had some lunch of course. Just now (around 5pm) I weighed in at 83kg. Apologies for waaay to much info, but this was prior to taking the first bath room break I've had since Pie in the Sky (around 11am, or 6 hours ago).

On this ride, I drank 1.6l of home made sports drink (containing in total 240g of maltodextrin, 40g of protein powder and couple teaspoons of magnesium supplement) and another maybe 3.2l of water. This is around 1l an hour which sounds in the ball park (don't forget - I used the bathroom only once on the ride). Ate 1 banana and one 'emergency' Gu about 30km from home. Had 3 eggs for breakfast. In retrospect an additional banana or a glass of magnesium supplement at breakfast would probably have worked wonders.

It was really rather hot when we finished (30C?) but I was actually quite happy with today's performance, especially given the silliness. That said, I very rarely cramp in the calf muscles but today had to spin out some horrible stuff in both inner thighs (at the same time - ouch!) almost at the very end of the ride. I have never cramped in this area before.

I'm basically only writing this as observations. Not sure it means anything, but someone might find this interesting. How does this amount of fluid loss/recovery compare?

P.S. See the silliness link for a word about what this ride was and why there was a little silliness Eye-wink

O's picture

I tested myself a few months back. Went for a run for an hour at medium intensity. Nice day, temp down about 22. Didn't drink or visit toilet and was 1.8kg's lighter when I got home. I'm about 100kg. I'd always used a dehydration estimate of 1ltr/hr as a guess when attempting to hydrate so was way out (hence the cramping in all these eundrance races!!) . Anyone have any idea what rate of fluid absorption the body can manage? I'm not sure I could even drink 1.8ltr an hour but there's no point if the body can't keep up.


psd's picture

Some good endurance nutrition info to be found here:

Talks about loss versus replenishment a fair bit. The numbers you're after are below. Interesting huh?

Fluids (ml) 1000-3000 (30-90 oz) ______500-830 (17-28 oz)
Sodium (mg) 2000__________________500-700
Fuel (Carb Cal) 700-900 _____________240-280

Fluids 20-33%
Sodium 20-35%
Fuels (Cal) 30-40%

Rob's picture

LOL... what a great term! Eye-wink

I'd read around quite a bit before trying the home made drink and most places (Hammer site too) reckon the body can only process... erm... assimilate... 60g of carbs an hour. This is why I put 120g of maltodextrin in an 800ml bottle (along with the other stuff) and spread that over a couple of hours, taking another 800ml in from a second bottle with pure water. You need some protein too though, especially for long rides so that's why a little of that is added (and I usually have an icy cold protein shake after a long ride - heaven!).

Darren put me onto the pure maltodextrin and it seems to work really well. The bottle here says 94% carbs and 382 cals per 100g. So the above drink gives around 230 cals/hour. For longer rides add in a little 'proper' food and you're almost there.

O's picture

Cheers PSD, unfortunately I think those numbers mean I shouldn't ever attempt another endurance event. DW100 last year was 7 hours for me. So I would have a net loss of about 1L an hour for a total of approx 7L

psd's picture

Yeah all that endurance stuff is really bad for you anyway - should just sit on the couch and assimilate some beers and chips I reckon Eye-wink

Rob have you got some more info on here about your DIY drink? Sounds interesting.

hawkeye's picture

What's the magnesium supplement you are using? No digestive system issues with the maltodextrin?

Logan's picture

keen to know about this secret homemade drink you have...

Is made of the skin of bogans and roadkill?

Buck's picture

I think Rob said it's mainly just maltodextrin which is just a carbohydrate. Same as what is in Hammer sports drinks and many other gels/drinks etc. I think he also told me once he puts some protein in it for longer rides. Same as Hammer Perpetuem.

Interested to know what he puts in for electrolytes though.

hawkeye's picture

If it's Skin of Bogan Laughing out loud you're after, I can supply the address of a certain driver of a turquoise Commodore resident in North Manly who would be an ideal candidate. And it wouldn't bother me in the slightest if you elected to enter him in the roadkill category first. Evil Laughing out loud

CJ's picture

There are some good things and some not so good things running through this tread... the concept of the home made sports drink is great in theory, but depending on where you get your "recipie" from will determine whether you hit the mark or get a great placebo. Even amongst the commercial beverages, as with any "commercial" product there are some good / effective ones and some real duds. I am often astonished at the rationale for the make up of these things. Sometimes there is very little real science them, or they hang their hats on 1 or 2 slightly left of centre scientific papers.
Having worked in the area of sports science for a lot of years, good / solid info is relativey easy to find, just don't get blinded by the marketing hype and snake oil merchants folks.
Robs home made beverage has a few limitations... while not wanting to shoot the mix or man down in flames... there is good science behind the better sports drinks out there. Here are a few things to consider

1. The main things a beverage needs to include are carbohydrate (CHO) to fuel the working muscles, and the electrolyte Sodium which helps to maintain fluid balance. Sorry Rob, magnesium is not lost in sweat, but is stored inside cells. So there is no need to replace this during exercise.

2. The CHO concentration in most sports drinks is approx 6-8%. This is the optimal concentration for emptying from the stomach and absorbtion into the blood stream from the small intestine. Combined with sodium, this creates a concentration gradient, to move the CHO from the gut into the blood stream. Rob's beverage (120g in 800ml is a 15% solution. which is way too strong).

3. A considerable number of good quality studies have found no benefit to the addition of protein, (such as Whey or BCCA) to a CHO electrolyte solution for use during exercise. To quote one author, " There is no established physiological mechanism by which protein intake during exercise should improve performance". If the CHO intake is suficient (~60 - 80g/hr) or (1g CHO/kg of body weight), there should be no limitation.

(Try the white bread and Vegemite sandwiches when next out for a long ride - White bread is High GI and readily absorbed, low residue ie: low fibre, Vegemite has about 3400mg of Sodium / 100g. Which is great for maintaining hydration and helps drive thirst).

4. There is real evidence to suggest that in the post exercise recovery period, (0 - 30 min after), CHO in combination with protein is ideal to replenish carbohydrate stores used when riding and to repair damaged muscle tissue. This "window" represents a time when the muscles are receptive or "sponge like" in their ability to take up nutrients... ready for the next taining session.
Have a look at the link below to the Gatorade Sports Science site for accurate, current information on a heap of these sorts of topics by proper expers in the field of physiology and sports nutrition. These folks are all highly respected, published and peer reviewed "gurus" in the area... enjoy... Chris

Rob's picture

Oh dear. Let's make a disclaimer: I'm no sports scientist so the below is just hearsay and rumor and has no actual scientific basis, but...

The point of the home made drink was to try and emulate the energy/protein of Perpetuem. I like Perpetuem but it has soy in it. I don't like Gatorade because it's carbs come from 100% simple sugars. Maltodextrin as I use, and is the main ingredient of Perpetuem is supposedly a more complex sugar that will not give you a sudden 'hit'. The spiel on this box here says:

Maltodextrin is a natural complex carbohydrate derived from corn starch. Consisting of long chains of glucose polymers, Maltodextrin is digested over a period of time, slowly releasing glucose into the blood stream. As a result there is no steep rise or fall in blood sugar levels

Out of interest, I made sheet with various comparisons of the various sports drinks and potions here:

Yes, I know one needs salt, but thanks for the reminder Eye-wink Before long rides I put loads of salt in my breakfast eggs (yum!). Buck and I have discussed putting a pinch of salt in sports drinks and perhaps the mix could benefit from that.

Yes, I know that 120g of Maltodextrin per 800ml is too strong. That's why I take a second bottle with just water and take 2 hours to drink both the home made drink and at least one bottle of water. Ie. If you say the home made bottle is 15% then the mixture sloshing around in my stomach will actually be more like 7.5% or less.

I included a little protein in the home made drink because there's some in Perpetuem and I read there could be some good to it. The way I figure it, I'm not really taking protein during or after exercise for more performance, am mainly taking it so am not wiped out the next day. Ie. to help recovery.

FWIW, here's what I put in the home made drink. For 2 hours, to be mixed in an 800ml bottle and drunk in conjunction with another 800ml bottle of water (or more):

- 120g pure Maltodextrin. This is 94% carbs, but only 16% comes from sugar as discussed above.
- 12g Phyto Protein. This is 88% protein.
- Teaspoon Ultra Muscleze. Mainly to replace magnesium. I'll admit this probably isn't ideal and some salt would probably help. Out of interest Endura has loads of Magnesium and Potassium in it as does Ultra Muscleze.

Anyhow, that's where the experimentation has lead so far and this seems to work for me.

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