Long Mynd Valleys

[jtinnion]

Hi Jim - did you get up to Bowland yesterday? HS offered me a lift to Stretton but unfortunately I had another seizure on Monday so wasn't running. Roll on the hospital appointment next Tuesday...

One thing I'd say is that thirst is not a great indicator of hydration. I did several experiments at university as part of a sports physiology course and urine colour is the strongest easily monitored indicator of hydration. How many times have we done a long training run or race in the summer and drunk 500-1000 ml afterwards and which has quenched thirst but still have orange urine an hour or two later. Lovely...

Hi Dr Bob

Yeah, Helen told me you'd had another one. Sorry to hear that. I managed to get finished in Warrington in time to come back for the Tuesday night run, then managed to bomb off down Long Synalds instead of finding the Townbrrok path on the way back. Paul was with me and his shoe broke, so it took us an extra twenty minute to get back. I think Terry's approach was best. He got to the car park having seen us in the wrong valley, assumed we'd either sort ourselves out or descend to Little Stretton, and went home for a nice cuppa!

Anyway, yes I realise that thirst isn't the best indicator, but I wasn't stopping to check me pee out half way round! The problem with hydration is that by the time you realise you're thirsty it too late really - performance is already being badly impaired. That's why I take the weight penalty if I'm going to take more than about an hour and a half and carry some fluid.

[Glenners]

But your V02 max hasn't changed. All that has changed is the mathematical expression of V02 max. Carrying an extra kilo of weight doesn't suddenly wipe fitness out(including anaerobic and lactate tolerance), but it will wipe out some speed and it won't necessarilly be 1.5%.

You'r right, as per, all I'm saying is the 1kg of weight previously mentioned isn't 1kg at the finish and isn't 1 kg after the first sip is taken, so the whole equation is out, regardless of the actual physiological effect of the weight carried!

[Mike T]

You'r right, as per, all I'm saying is the 1kg of weight previously mentioned isn't 1kg at the finish and isn't 1 kg after the first sip is taken, so the whole equation is out, regardless of the actual physiological effect of the weight carried!

You will still weigh 1 kg more than you otherwise would have without the drink - so the approximate 1.5% handicap is still there - whether the water is on your back or in your body. The question is - do you need it on a relatively short event like Longmynd in such benign temperatures. We are well designed - using glycogen liberates water, and CHO/fat + O2 is converted into energy heat CO2 - AND water and both of these sources of water can be enough to prevent significant dehydration, even in the presence of (performance enhancing?) weight loss.* Of course eventually dehydration occurs and you are then unable to sustain your normal % of VO2 max, and performance declines. It may be that in theory a bit of dehydration at the end is worth it - given the advantage of not having the weight handicap of carried/consumed water. NOT to be recommended - but I just wanted to make the point.

* See this reference for more on exercise associated weight loss NOT NECESSARILY being the same as dehydration - to quote the last sentence of the paper : "A significant loss of body mass - perhaps of the order of 1-3% of pre-exercise mass - may be incurred without an effective hypohydration resulting."

Maughan, Ronald J., Shirreffs, Susan M and Leiper, John B. (2007) " Errors in the estimation of hydration status from changes in body mass", Journal of Sports Sciences, 25:7,797-804.

[Mike T]

From an article I did for our local running club's magazine - yes, they are that desperate!
"Running a marathon, at 100 calories a mile, takes approximately 2600 calories. About 25% of this results in work/movement but 75% just results in heat which has to be dissipated to the environment or we would quickly become hyperthermic and die. 75% of 2600 is 1850 calories of heat to lose, and as long as the ambient temperature is less than 20C it is estimated that sweating only has to dissipate half of this ( or less as it gets colder ) as the rest is lost through radiation and convection. 1ml of sweat loses about 0.6 of a calorie so 925 calories needs about 1.5 litres of sweat. But glycogen breakdown liberates water at 2.7mls/gm - if half of the energy of the marathon is derived from glycogen at 4 calories/gm (and the rest from fat ) then about 800 mls of water is liberated and about another 400mls is generated as a by product of energy use ( carbohydrate plus O2 being converted to CO2,H2O and energy ). So the body has come up with 1.2litres of the 1.5 needed. But during exercise our temperature rises, so we don't need to lose all the heat we generate. A typical temperature rise would be from 36C to 39C, and as each degree of temperature increase is about 60 calories, or 100mls of sweat, we can subtract 300 from 1,500 leaving 1,200 - so there is no need to drink at all!"

[Marvin]

You will still weigh 1 kg more than you otherwise would have without the drink - so the approximate 1.5% handicap is still there - whether the water is on your back or in your body. The question is - do you need it on a relatively short event like Longmynd in such benign temperatures. We are well designed - using glycogen liberates water, and CHO/fat + O2 is converted into energy heat CO2 - AND water and both of these sources of water can be enough to prevent significant dehydration, even in the presence of (performance enhancing?) weight loss.* Of course eventually dehydration occurs and you are then unable to sustain your normal % of VO2 max, and performance declines. It may be that in theory a bit of dehydration at the end is worth it - given the advantage of not having the weight handicap of carried/consumed water. NOT to be recommended - but I just wanted to make the point.

* See this reference for more on exercise associated weight loss NOT NECESSARILY being the same as dehydration - to quote the last sentence of the paper : "A significant loss of body mass - perhaps of the order of 1-3% of pre-exercise mass - may be incurred without an effective hypohydration resulting."

Maughan, Ronald J., Shirreffs, Susan M and Leiper, John B. (2007) " Errors in the estimation of hydration status from changes in body mass", Journal of Sports Sciences, 25:7,797-804.

So when I exercise I put on weight? Right?

[Marvin]

...and lose weight when I eat?

[Mike T]

Please elaborate - the Shirreffs' paper I refer to - our articles were compiled totally independently - contains very similar arguments/calculations - and I did run it past her as an academic exercise physiologist to see if I had made any major or silly errors.

[Glenners]

Ran for two hours Sat morning, deliberatley didn't take a drink or gels etc, (though my mate did have plenty in case I needed it), has to be said that I didn't really miss it so maybe your right Mike T. I wasn't racing round though so difficult to say if there would have been further effects if I was running harder or it was a warmer day.

[andy k]

PLease could someone post the race route or a list of checkpoints for this ?
I'm down there at the weekend and fancy a run round

cheers

[beasty1711]

All the info is here

http://www.merciafellrunners.org.uk/node/236