Yet Another Cycling Forum

General Category => Audax => Topic started by: phil w on June 03, 2019, 05:32:31 pm

Title: Rehydration in Hot Weather on Audaxes.
Post by: phil w on June 03, 2019, 05:32:31 pm
After failing on Windsor Chester Windsor 600 over the weekend, due to hot weather and dehydration, it's time to review my hydration strategy / tactics.  I haven't used hydration electrolyte tablets for some years preferring plain water and salty snacks but as has has just been borne out, this isn't enough as temps soar.

So I'm thinking a combination of electrolyte tabs in water, salty snacks, and diorlyte sachets as backup. I would class myself as a heavy sweater of salt.

What are other Audax riders doing, how much are you drinking, how much electrolyte are you putting in your water (bottle size for context please)?  How much are you drinking at stops?  Seems strange to be asking after a few years of Audax but I clearly haven't cracked dealing with hotter weather.  Any other tips welcome.

I have three weeks before I attempt to finish off my PBP qualification resit exam. So have time to try a small set of some variations. 
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: hellymedic on June 03, 2019, 05:48:30 pm
Don't forget external cooling!

Wetting your clothing does not use much water and can effectively chill you well. Washing off excess salt will improve the efficiecy of perspiration.

Enjoy ice lumps and ice-cream when available.

I don't know if you have a h*lm*t impairing heat loss from your head but this needs to be considered.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: dubya on June 03, 2019, 05:48:55 pm
Sorry to hear WCW didn't work out for you, this weekend was such a hike in temperature it was a surprise.

I believe that hydration tablets have been largely debunked.  Several studies have shown that you just need to drink water. However (there is always a however) the added flavouring in the electrolyte tablets has the effect that you drink more!

I find this has been true for me too, if I just have a water I do not drink as much as I do when I have a tablet in bidon.

I set my Garmin to auto lap every 5km. When I hear the little lap tune (between 11- 15 mins) I take a glug from the bottle.  Little and often is the best way.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: S2L on June 03, 2019, 05:50:34 pm
Thyroid OK?
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: phil w on June 03, 2019, 05:52:23 pm
I don't know if you have a h*lm*t impairing heat loss from your head but this needs to be considered.

Nope don't have that problem, but could have soaked my cap in water had I thought some more. I prefer to keep the cap on in direct sun but will remove if clouded over and at night time.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: phil w on June 03, 2019, 05:54:43 pm
Thyroid OK?

You are going to have explain that one.  I'm on no medication, and no diagnosed illnesses. What would be the symptoms of a duff thyroid?  I presume symptoms (whatever they may be) would show up outside long hot rides?
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: marcusjb on June 03, 2019, 06:01:05 pm
I believe that hydration tablets have been largely debunked.  Several studies have shown that you just need to drink water. However (there is always a however) the added flavouring in the electrolyte tablets has the effect that you drink more!

I find this has been true for me too, if I just have a water I do not drink as much as I do when I have a tablet in bidon.

I will totally go with that - I know I drink more with tablets than without.

Phil - have you tried arm coolers and/or leg coolers?

Again, I am sure that there's a chunk of snake oil in marketing materials for them, but I have found arm coolers very good when touring etc. in hot climates.

Whilst obviously not dealing with 40 degree plus etc., you react poorly to the heat, so maybe look at what RAAM riders etc. use in the desert sections?
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: zigzag on June 03, 2019, 06:11:59 pm
i've been out on saturday, it was quite warm (28-29?) but movement from riding was enough to cool me down and not sweat. one doctor i spoke to advised to avoid sweating if possible as this is an "emergency" response to get the temperature down; it then takes more time and effort for the body to get back into it's normal state and restore the balance of minerals. i only use electrolytes if i'm sweating, which i did while riding in 30-40+ degrees, usually one tablet per bottle and one bottle an hour (on saturday - i only had one 0.7l bottle for 175km and did not feel too dehydrated). i have my garmin set up to alert me to drink every 20min.
wishing you good luck on your qualifiers!
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: JonJo on June 03, 2019, 06:20:46 pm
(on saturday - i only had one 0.7l bottle for 175km and did not feel too dehydrated).

Me too. Did 200k in slightly cooler conditions and rain for the final 40k helped but I find drinking more than that makes me pee so much that I have to stop every 5 - 10k.

If it gets really hot I try to soak my cap to keep me cool.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: S2L on June 03, 2019, 06:23:19 pm
Thyroid OK?

You are going to have explain that one.  I'm on no medication, and no diagnosed illnesses. What would be the symptoms of a duff thyroid?  I presume symptoms (whatever they may be) would show up outside long hot rides?
Not duff, but hyper active
Check the symptoms for hyper-thyroidism and see how many boxes you tick...
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: phil w on June 03, 2019, 06:39:52 pm
Thyroid OK?

You are going to have explain that one.  I'm on no medication, and no diagnosed illnesses. What would be the symptoms of a duff thyroid?  I presume symptoms (whatever they may be) would show up outside long hot rides?
Not duff, but hyper active
Check the symptoms for hyper-thyroidism and see how many boxes you tick...

None of the symptoms listed on Wikipedia
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Wycombewheeler on June 03, 2019, 06:51:56 pm
I've always just used water with soft drinks at controls. Including when I did meridian hills perm in weather better than forecast when I drank 7 litres and didn't pee at all. What symptoms make you think you need electrolyte tablets?
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: phil w on June 03, 2019, 06:55:38 pm
Looking up heat exhaustion I had most of the symptoms



So reasonably happy that's what it was.

Treatment seems to includes recognizing the symptoms, stopping the activity, and moving to a cooler environment. Rehydration with water or a sports drink is the cornerstone of treatment for heat exhaustion. So seems more water, and ways of keeping cooler , and stopping to cool down when necessary.

So if not hydration tabs how much water are people drinking? Is salt loss through sweat really a non issue?
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: mattc on June 03, 2019, 06:56:28 pm
you can get your sweat analysed. Normally I shy away from such "snake oil", but the science seems pretty convincing, and I don't think it costs very much.

Look at rider's backs on a hot day - some have amazing white patterns on their back, yet some no mark. There is quite a difference.

I'm currently a great believer in electrolyte tablets. The science convinces me (so far!), and my sunstroke symptoms have reduced *massively* since I started using them, despite growing up surrounded by the "keep drinking!" ethos.

Oh and don't forget acclimitization - for many, this was our first hot long ride of the year. The body makes miraculous adjustments as the summer progresses, and magically events like PBP (i.e. late August, or later) become quite survivable.


Good luck!
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: LittleWheelsandBig on June 03, 2019, 06:56:52 pm
I find ice creams and chilled drinks are worthwhile for lowering body temperature when riding in hot weather. Lukewarm water from my bidon, not so much. It worked well when riding in Oz and the Italians did it too when we rode Mille Miglia.

Given the amount I sweat even in cool weather and the visible salt-stains in hot weather, one of my two bidons often has something salty in it.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: yanto on June 03, 2019, 07:00:23 pm
Being enclosed with limited through flow when the heat and humidity strike I sweat, I mean it runs off, if I didn't have a drain hole in the seat I would be sitting in a puddle. I normally drink about 1.5l per 100k when it is hot (little and often), this with tablets at minimum dosage, but at stops I drink another 0.5 - 1 litres, often cold milk. I find it physically hard to drink more and the longer the ride, the less I feel like drinking, as a result I'm always dehydrated to some extent which may take a day to rectify.

Sorry to hear about problems on the 600!

ETA, don't forget solar radiation, wear light colours not dark.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: phil w on June 03, 2019, 07:13:23 pm
I've always just used water with soft drinks at controls. Including when I did meridian hills perm in weather better than forecast when I drank 7 litres and didn't pee at all. What symptoms make you think you need electrolyte tablets?

Mostly the amount of dried salt on my skin and face, hat, and jersey plus the fatigue and muscle cramps. Maybe it's not the cause but there does seem to be a lot of salt. So I'm assuming the salt is the issue rather than liquids in general. But others posts are implying maybe I just need to drink a lot more and find ways of staying cooler and stopping to cool down again as necessary.

Here's the cap I was wearing till the sun went down. With the white all being sweated out salt.

(https://www.dropbox.com/s/y4affgwk8ng4hkl/Salt.jpg?raw=1)
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Ajax Bay on June 03, 2019, 07:15:18 pm
For long efforts in warmer conditions, hydration is obviously necessary but easy to concentrate on that when keeping one's body core cool is proportionately more important. In such conditions, people are more likely to go down with heat injury than because of dehydration. The cooling effect of cycling speed means this is more markedly the case for runners.
I offer this anecdote (which has influenced my opinion on this). The Three Peaks Yacht race (starts 15 June this year, from Barmouth (TINAT note)) takes in Snowdon (normally at night), Scafell Pike (often by day) and then a day plus later, Ben Nevis. The Scafell Pike leg is/was the longest: from the coast at Ravenglass (port changed nowadays) to Wasdale Head (20km); up and down (10km + 900m); back to boat. Three plus hours done in the middle of a hot June day, well hydrated, heading back with 10 miles to go at a brisk but steady pace (90 minute half marathon pace (with rucsacs)) my heart rate started to rise markedly (to above 180bpm), with no associated increase in pace and no self-perceived increase in effort/exertion. So the next time we reached our support, water went not down my throat but over my hat/head, shoulders down my back and front and on my legs. My HR dropped immediately back to 'normal' 160bpm (say). There is an inclination not to 'waste' water: it's needed for drinking. It's needed for body cooling too.
So my advice is (as @Hellymedic says): regular 'external' cooling and don't be concerned, any more than normal, with additional hydration: drink to thirst. This means keeping at least one bottle for plain water, whatever potions/tablets/powders you care to add to the other.
In a previous 'life' the Institute of Naval Medicine led some careful research into what liquids were best for maintaining proper hydration over a hard endeavour of 8 hours (across Dartmoor), in addition to eating ordinary food, a banana or 5 and a pasty (salted). The conclusion was:  . . . . . water.
Phil W said "Rehydration with water or a sports drink is the cornerstone of treatment for heat exhaustion."
I can find where you've quoted this from but am surprised at this. The 'cornerstone' of treatment (indeed ideally for prevention) for heat exhaustion must be body cooling.
To quote another site (on treatment):
"Anyone who suspects that they have heat exhaustion should immediately take steps to cool down. These can include:
    moving to a shady location
    removing one or more articles of clothing
    resting out of the sun
    turning on a fan or the air conditioning
    running cool water over the skin or applying cool, wet towels to the body
    drinking fluids such as water and sports drinks"
Shade, strip, fan, soak, and only then, drink.
If you have pint of water, most of it needs to go over the patient/victim, not down their throat.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: bludger on June 03, 2019, 07:28:18 pm
Yes quite right heat exhaustion can't be 'drank away' unfortunately the squaddies doing the fan dance thought they could just suffer through it with enough to drink which led to their deaths.

I've only done one mega hot Audax which was the Locked and Boulted populaire in 2018. It peaked 31° at noon - I saw many people stopped and sheltering under trees as it was so hot.

In the last 10 km or so in Marlow I ran out of water and thought (being a local at the time) that I could just crunch on instead of stopping at a pub to refill. This was my worst cycling decision ever, and I spent an hour at the Arrivée drinking sugary drinks, sat down under a paradol with a soaked bandana mumbling incoherently with a headache.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Chris S on June 03, 2019, 07:32:07 pm
Not wanting to piss on your cornflakes, but it's possible this doesn't have a solution.

You clearly sweat profusely when hot, and dump all your electrolytes all in one go, which causes a cascade of symptoms from which there is no return - while you're still trying to carry on doing the very thing that started it all. It's not like this is the first time this has happened, is it?

I can ride in heat without too much trouble, provided the route is moderate, relative to my current fitness - assuming I can rest often and moderate my effort. These are not necessarily things you can do on a timed event when you're being chased by a time-limit.

There's a finite rate at which you can absorb water and electrolytes; if your physiology is such that it dumps your water and salts faster than you can assimilate intake, then your performance in hot weather is always going to be limited.

Here's hoping you can find a solution, or at least a compromise that can just about keep you going when it's hot. Not everyone can - some folks just have to hide when the mercury climbs.

Did you perhaps ride too hard in the run-up to onset of symptoms? It's easily done - I know!
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: simonp on June 03, 2019, 07:37:11 pm
I reckon I was getting that way on the final day of LEL 2013 which was one of the hottest days of the year if not the hottest. It was resolved by sitting under a tree eating a magnum and the sun setting and pouring water over my head.

You’ll find heat acclimatisation helps. I trained indoors Saturday and Sunday this weekend and ended up drenched in sweat. Even on Saturday when it was an easy zone 2 spin. You can simulate hot conditions by keeping the window closed and turn the fan down or even off.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: bludger on June 03, 2019, 07:39:43 pm
How about using long sleeve close-fitting technical clothes? E.g. the coolmax leg and arm warmers (seems counterintuitive I know...).
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: hellymedic on June 03, 2019, 07:43:35 pm
I did some very hot rides back in the day, without issues.

I really think much of the battle is dealing with excess heat before it creates issues with the body attempting to compensate with sweating. A wet flannel can cool you quickly and cheaply.

Sun gloop will impair your sweating.

Ice/Ice cream and slush drinks are good when available.

You will drink more if your drink has some flavour. I liked diet squash and half-strength fruit juice. Full strength fruit juice is hypertonic, as is full sugar cola. This means the body needs to pass water into the gut to be absorbed, which is sub-optimal.

If you are eating savoury food in normal amounts, there will be enough salt here, otherwise you might consider electrolyte drinks.

I have not seen much Isostar/Gatorade recently. Have they disappeared? I think various forms of Lucozade Sport are still available. Avoid anything that's more than 5% sugar.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Ian H on June 03, 2019, 07:50:20 pm
My solutions, as required, are minimal clothing – single layer with full-zip jersey, regular drinking, and the occasional pub-stop for orange & lemonade with crisps (or similar salted comestibles). 
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: phil w on June 03, 2019, 08:42:34 pm
How about using long sleeve close-fitting technical clothes? E.g. the coolmax leg and arm warmers (seems counterintuitive I know...).

I think there's something to be said for this. I was reading that once there is too much sweat on the skin it's not able to evaporate and cool you. So what does the body do in response, produce more sweat, which doesn't evaporate. The wicking fabrics, one trademark you mention above, can keep you cool by wicking enough sweat away that the remaining sweat on the skin is able to evaporate , cool you, and stop or slow yet more sweat.  I wear lightweight merino tops on the recumbent and I find I sweat much less and feel drier than cycling tops. Maybe it's time to drop cycling tops and just wear lighter weight cooler merino stuff if hot weather is forecast.  Bib tights when upright don't help with all the extra material. It's not as if I don't have storage solutions otter than three pockets of a jersey on an Audax. The arm coolers Marcus mentions may also work on a similar principle.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: phil w on June 03, 2019, 08:49:19 pm

I really think much of the battle is dealing with excess heat before it creates issues with the body attempting to compensate with sweating. A wet flannel can cool you quickly and cheaply.

Wouldn't it be great if all shops sold small bags of ice designed to perfectly fit inside a cycling cap?

You're tight of course, I'm am loath to pour water over myself, seeing it as a waste.  Will think more on this option and try this if I find myself overheating on another ride. Plus stop and rest in shade a while.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: hellymedic on June 03, 2019, 08:49:30 pm
I can't say I really liked these technical wicking tops when it was really hot, TBH. They left my skin wet and sticky, which wasn't the case with old-fashioned cotton.

I am a Luddite (but was never DNF due to overheating).
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: phil w on June 03, 2019, 08:53:26 pm
I can't sayI really liked these technical wicking tops when it was really hot, TBH. They left my skin wet and sticky, which wasn't the case with old-fashioned cotton.

I am a Luddite (but was never DNF due to overheating).

Well the above is what I get from the polyester cycling tops but not from merino / smart wool.

On the other hand I deal well with cold and can often be riding in shorts and with bare arms when others are fully togged up.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: PneumaticBliss on June 03, 2019, 10:06:32 pm
This is not a simple topic - made less simple by sport drink marketing propaganda.  care is required - dehydration doesn’t necessarily have anything to do with being too hot, and sweating might raise your electrolyte levels not lower them.

Useful series of articles here:

https://sportsscientists.com/2007/10/fluid-intake-dehydration-and-exercise-part-i-history-of-fluid-intake-and-a-conflict-of-interest/

Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: simonp on June 03, 2019, 10:22:24 pm
TrainerRoad podcast discussed sodium loading in episode 201 which I happened to listen to tonight. I’d take such ideas with a pinch of salt.

IGMC.

They’ve covered heat acclimatisation in the past. I think this is certainly something you can work on on the turbo.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: hellymedic on June 03, 2019, 10:32:37 pm
This is not a simple topic - made less simple by sport drink marketing propaganda.  care is required - dehydration doesn’t necessarily have anything to do with being too hot, and sweating might raise your electrolyte levels not lower them.
Useful series of articles here:
https://sportsscientists.com/2007/10/fluid-intake-dehydration-and-exercise-part-i-history-of-fluid-intake-and-a-conflict-of-interest/

My point is that trouble with hydration occurs after a rider has become too hot and is unable to balance water and minerals. An overheated rider may not absorb food and fluid well if blood is shunted to the skin and away from the gut.

All the smart drinks in the world won't cure someone who is puking until they cool down and stop vomiting. At this point, it may be too late to save a ride.

My general strategy for Audax success is to address minor issues BEFORE they escalate into major problems.

That is what has worked for me.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Chris S on June 03, 2019, 10:41:28 pm
What even IS the evolutionary driver behind the whole - "Hey, we need to assimilate water and salt for the next few hours because it's freakin' hot, so let's commence a PUKE-A-THON!". Homo Sapiens - making zero sense, since 200k BC.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: grams on June 03, 2019, 10:56:18 pm
I had a check of the weather data along the route and it looks to have peaked at 23 degrees, which matches my recollection of it being hot but not roasting. It sounds to me like something more complicated happened to you than simple dehydration in hot weather. I wouldn't like to speculate on what though.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: hellymedic on June 03, 2019, 10:57:50 pm
Anyone with a hap'orth of sense would stop cycling, strip off, sponge down and rest before confounding the issue with a SCIENCE overload.

Primitive man would not drink if nauseous...
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Ajax Bay on June 03, 2019, 11:29:15 pm
This is not a simple topic - made less simple by sport drink marketing propaganda.  care is required - dehydration doesn’t necessarily have anything to do with being too hot, and sweating might raise your electrolyte levels not lower them.

Useful series of articles here:

https://sportsscientists.com/2007/10/fluid-intake-dehydration-and-exercise-part-i-history-of-fluid-intake-and-a-conflict-of-interest/
Thank you very much for providing that link - well worth reading imo. Drink to thirst.
Deep in the 4th article is this (slightly edited):
"My sweat tastes salty

"Yes, it certainly does, and that is because it does contain some sodium. However it contains profoundly less [per volume] than the fluids in your body, and is still mostly water—body fluids have a sodium concentration of 140mM while sweat has a value of 20-60mM. Therefore when you remove a liter of sweat from your blood, it has much more of an effect on the volume compared to [an effect on] the solutes (sodium), and what happens is that the osmolality rises in response to sweat losses. This is absolutely crucial to realise – you cannot lose sodium, even if you are a “salty sweater”. If the sodium content of the blood is dropping, it’s because you’re drinking too much water [in extremis leading to hyponatremia - more dangerous than dehydration per se], not because you’re sweating sodium! In fact, a very interesting study was published in 1992 by Robert Cade (Gatorade). During a marathon 3 groups of runners were given Gatorade, or 1/2 Gatorade (half water, half Gatorade), or water. The really interesting finding was that the water group maintained their sodium concentration (a surrogate for the total osmolality) just fine, while the Gatorade group actually increased its concentration. This explains why people drink more of a sports drink compared to water—the sports drinks keep your osmolality higher and therefore makes you thirstier. So instead of lowering osmolality, which is what your body wants you to do, the sports drinks raise it. Seems kind of counter-intuitive, doesn’t it?"
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Rainbow Dash on June 03, 2019, 11:39:22 pm
I find blackcurrant Dioralyte works quite well in warm conditions - unlike some sports drinks it is easy to drink without feeling sick.

If you want to increase the amount you drink you could try a CamelBak style pack. They make drinking easy compared to bottles and hold up to 3 litres which would keep you well hydrated if you fill up at each control. Not sure whether it would be comfortable to wear one on a 600 though.

Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: madcow on June 03, 2019, 11:51:29 pm


Sun gloop will impair your sweating.



Don't forgo sunscreen though as the cumulative effect of all that UV and IR will increase your body temperature.
If you have sensitive skin or it's being exposed to sun for the first time, then use SPF 30 or even 50.

I wear a large handkerchief round my neck during hot weather. It protects the back of the neck, absorbs sweat and when soaked with cold water, it helps to keep me cool.
It can also be used as a facecloth.

+1 for the Dioralyte or similar, but really you have to force or train yourself to drink more often.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Exit Stage Left on June 03, 2019, 11:57:01 pm
The problem is not helped by the reliability of modern cars, and the closure of filling stations.

Quote
in 2000 there were around 14,500 filling stations in the UK, which has shrunk to around 8,400, with 300-400 closing every year, up until five years ago.

Every filling station had an outdoor tap, where you could fill bottles, and if it was really hot, dowse your hat and shirt, and fill your shoes with water. These days radiators don't need topping up, and the garage store wants to sell you bottled water. There are always churchyard taps, but you have to know where they'll be.

I remember cramping big-time on the 24 in 1999, in 30+ degrees, stopping at a garage cum shop, and buying 500gm of salt. I don't think the garage is there now. Lots closed down because they couldn't meet changed storage regulations.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Kim on June 03, 2019, 11:57:13 pm
ETA, don't forget solar radiation, wear light colours not dark.

Noting that the colours your eyes are sensitive to may not accurately reflect the albedo of the jersey (https://yacf.co.uk/forum/index.php?topic=12029.msg1520388#msg1520388).  I'd hope that most manufacturers of proper cycling kit would get this right in their choice of dyes.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: SR Steve on June 04, 2019, 12:06:02 am
In my experience heat exhaustion can be caused by too much direct sun to the head and neck areas. That can make me nauseous and exhausted without even doing any activity or getting dehydrated. I always wear a helmet when cycling regardless of how hot it is, but switch to my best white one with plenty of vents when it's going to be hot. I find this insulates my head from the sun and as long as I'm moving air flows through the vents keeping my head cool.

On my hottest three rides last year, Mille Pennine, Mersey 24 and Dolomites Super Randonnee 600, I wore white leg and arm warmers/coolers throughout the events and found they worked well, reflecting some heat and giving a cooling effect as sweat transpired through them. I also wore shorts with coolmax inserts and thin short sleeved jerseys with no base layer and long zips during the heat of the day. The arm and leg warmers/coolers also saved me from having to bother with sun cream.

I'm not keen on drinking plain water especially when it starts getting warm so I use white or silver coloured bottles to delay the warming process and I put a high5 zero tablet in each 750ml bottle as this makes it tastier as well as replenishing any electrolytes I might be loosing. I usually have a couple of scoops of energy powder in each bottle too. I rode a DIY 200km on Saturday and wore my thin long-sleeved old AUK top, dhb shorts and white helmet. My legs got slightly sun burnt, but I was otherwise ok. I drank the two bottles of energy/electrolyte drink I'd made up at home and felt fine during the ride, but I was sweating a lot after I'd finished so drank a protein shake and two pints of water shortly after finishing. If it had been the first 200km of a 600km I would probably have drank an extra litre during the ride, but as a stand alone 200km I got away with drinking less and did the whole ride non-stop.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: quixoticgeek on June 04, 2019, 12:59:43 am
I find blackcurrant Dioralyte works quite well in warm conditions - unlike some sports drinks it is easy to drink without feeling sick.

If you want to increase the amount you drink you could try a CamelBak style pack. They make drinking easy compared to bottles and hold up to 3 litres which would keep you well hydrated if you fill up at each control. Not sure whether it would be comfortable to wear one on a 600 though.

I'm gonna actually suggest that a camelback style bladder system, has a weakness. You can't easily tell how much you have drunk. You may think you've taken a sip every few minutes, so that must be loads, but then find you've still got 2 litres in the bladder. This is more or an issue when it's in a frame bag, or when there is other stuff in the backpack when back mounted.

Personally I like a 1L bottle. I  carry 1 or 2 of them, depending on temperature.

Last summer I did.3 200k DIYs in 6 days, in ~34°C temps. There was minimal breeze, next to no shade, and little cloud cover. I wore a white helmet, a short sleeve merino jersey, shorts, short socks, and what felt like half a litre of factor 50... On each ride Iost count of how much liquid I took in at 6L. Mostly water, with some coke and Fanta at cafes. On the hottest day of the 3, despite the constant input of liquid, I went 8+ hours between toilet visits. I planned my rides based on available water sources (did I mention the drinking water POI overlay of Osmand?), Literally riding from drinking tap to drinking tap. Usually 40-50km between each. Consuming at least 1l during that distance.

My clothes had a coating of salt crystals by the end of each day. There were times when having filled my bottle I had a brief moment of trying to decide, do I drink it, or pour it over my head. On one occasion where I did do spray it over my head to cool down, it just washed all the salt into my eyes, which stung... On only one of the rides did I wake up the next day dehydrated. Which was soon fixed. I didn't take any fancy hydration salts, but did have a packet of ready salted crisps each day, as well as a portion of salted fries.

I'm of the view that the trick is to drink lots, starting before you start riding, to keep a good idea of how much you've drunk, and if in doubt, drink.

J
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: bludger on June 04, 2019, 01:26:57 am
I have long wrestled with the colour question - for instance we take it as a given that light colours reflect the light away, but in the middle east and Africa it seems dark colours are very popular, such as among the Tuareg.

I have a probably more than  questionable theory that light colours will reflect energy back inside to the body as much as they 'bounce them away' from the surface, and that dark fabrics better radiate the heat away from the body.

In any case it seems to me that the research finds the whole thing makes little odds on that question https://science.howstuffworks.com/science-vs-myth/everyday-myths/light-colored-clothes-in-hot-weather.htm

Certainly the rocks will melt under the sun before I wear white shorts.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: JBB on June 04, 2019, 07:13:32 am


Sun gloop will impair your sweating.



Don't forgo sunscreen though as the cumulative effect of all that UV and IR will increase your body temperature.
If you have sensitive skin or it's being exposed to sun for the first time, then use SPF 30 or even 50.

I wear a large handkerchief round my neck during hot weather. It protects the back of the neck, absorbs sweat and when soaked with cold water, it helps to keep me cool.
It can also be used as a facecloth.

+1 for the Dioralyte or similar, but really you have to force or train yourself to drink more often.

I've used the wet handkerchief round the neck to great effect. Simple to carry and evaporative cooling to some major blood vessels. I wasn't hot enough to need it on Saturday. I drank a lot, especially at the controls before eating. Other than that I was wearing a lightweight merino vest and thin summerweight club cycling top.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: mattc on June 04, 2019, 07:15:33 am


Certainly the rocks will melt under the sun before I wear white shorts.

 ;D
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: mattc on June 04, 2019, 07:19:11 am
They’ve covered heat acclimatisation in the past. I think this is certainly something you can work on on the turbo.
turbo???

What's wrong with a nice Arran jumper?

(one can solve problems without a turbo ... )
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: madamemugwump on June 04, 2019, 07:58:46 am
I've used the wet handkerchief round the neck to great effect.

I wear a gel one and found it helps. Soaked in cold water, the cooling effect lasts hours. As someone who suffers in the heat my other tactic is simply not to ride. Not an ideal solution by any means, and obviously not one that is conducive to qualifying for (nor indeed riding) PBP but it does nonetheless remain an option.

Some people have winter off seasons, I have a summer one!
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: andyp on June 04, 2019, 08:47:02 am
hi,
I met a GP from Melbourne at the start of PAP: he had been found fitting at the side of the road at the end of day 1 of a hot US 1200 a few years ago: he almost died, and has no recollection at all of the journey to the US, or the ride! He'd been drinking water all day. He now adds pure salt to his water bottles by the teaspoon - he assured me it's all you need, and that you do need it. he wrote a well researched / definitive article in the Australian audax newsletter on the subject which would be worth searching for I think.

+ 1 to looking out for streams, water fountains, water troughs to wash your face / dunk your head / cap / feet in on hot days: it drops your core temp, and is a complete reviver.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Wycombewheeler on June 04, 2019, 08:54:12 am

I really think much of the battle is dealing with excess heat before it creates issues with the body attempting to compensate with sweating. A wet flannel can cool you quickly and cheaply.

Wouldn't it be great if all shops sold small bags of ice designed to perfectly fit inside a cycling cap?

You're tight of course, I'm am loath to pour water over myself, seeing it as a waste.  Will think more on this option and try this if I find myself overheating on another ride. Plus stop and rest in shade a while.
I wouldn't think of it as a waste. If you're only using enough to wet your garments it's just short circuiting the sweating process. It will only end up there anyway if you drink it, taking with it less easily replaceable salts.

If you are feeling hot/sick then cooling is the main requirement. I would think electrolytes in water are what's missing if you are cramping up despite drinking enough liquid.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Ben T on June 04, 2019, 08:58:13 am
There's a lot talked about in this thread of salt being a good thing and I'm sure to some extent it is, but personally I avoid eating anything too much of anything very salty e.g. bacon, on an audax as it makes me too thirsty.
I find from subsequent thirst levels McDonald's is more salty than it tastes.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: earthloop on June 04, 2019, 11:18:35 am
One tip that I haven't seen mentioned yet: dampen your entire jersey (either under the bathroom tap in a pub or in a plastic bag with a squirt of water by the roadside) for that lovely "oooh cold cold cold" feeling as you put it back on. I find that once it's damp it's easy to top up the dampness via a squirt over the shoulder or down the back of the neck, whereas doing that with a dry jersey leads to wasteful runoff.

Applying water directly to your skin (rather than via your digestive system and sweat glands) isn't wasteful unless you spill lots IMO, and it preserves electrolytes and cake digestion capacity.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Exit Stage Left on June 04, 2019, 12:04:52 pm
The cooling effect of movement means that cycling allows a greater heat output from exercise than running. That ceases to be the case on hills, especially for heavier riders.

The heat output is related to power, on a hill you are going slow, so evaporative cooling is less, and you're bathed in sweat. On the flat you'll be going a lot faster; you'll still be sweating as much, but it evaporates at a faster rate, the build-up of salt is the main clue to that. The body also loses a lot of heat through breathing, which is why we pant in the heat.

One critical point is arrival at a control. It's possible to have been sweating profusely while riding hard, without knowing it. When you stop, you are instantly covered in sweat, and will pant. You can see that sort of heat shock at PBP, it forms part of an edit I did of footage from 1983 and 1987. https://www.youtube.com/watch?v=pmcui9ynsus

It's important to 'warm down' over the last couple of Km into the control in hot weather.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: CrazyEnglishTriathlete on June 04, 2019, 12:55:23 pm
Acclimatisation works for me.  Not very helpful when the UK throws a random hot day early on in the year, but something I think about if I know I'm likely to get hot weather.  The most sustained heat I've ridden in was the Mille Miglia in 2010, fortunately that was a hot summer in the UK and I took plenty of opportunities to ride through the afternoon and tune my body, I deliberately picked hilly routes to simulate risk of overheating.

I used to take electrolyte tablets and have some in reserve, but I find they can mess with my stomach, so will often revert to petrol station staples: salt & vinegar crisps, prawn sandwiches, and pork pies, all of which have salt levels through the roof and I seem to be able to absorb these better.  (warning - food & digestion related advice varies highly between people)

I found on Mille Miglia that wetting the helmet (in a water fountain) worked quite well at cooling the head and helped, particularly on the hottest day.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: iscunonove on June 04, 2019, 01:06:15 pm
Like I'm sure others do, I run two bottles, one with flavour & electrolytes, the other with plain water. In really hot weather as much of the water gets poured over me head and back as gets drunk. Also traditional cotton cap (no helmet). And no stupid hard efforts.... smoothly does it.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Matt Robinson on June 04, 2019, 01:47:19 pm
Hi Phil,

On WCW this weekend I carried a 750ml and a 1000ml bottle. On each leg I drank all of my water. Every 750ml bottle was also mixed with a High 5 Zero tablet. So over the course of WCW, thats 17.5 liters of water with 10 tablets. At each control I generally also had a small glass of squash and a cup of coffee.

I weighed myself before the event and the day after the event. The day after I was still 3kg lighter than when I started, so I still wasn't drinking enough, even though I reckon I went through 20 liters!

Matt
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: hellymedic on June 04, 2019, 02:48:52 pm
This is not a simple topic - made less simple by sport drink marketing propaganda.  care is required - dehydration doesn’t necessarily have anything to do with being too hot, and sweating might raise your electrolyte levels not lower them.

Useful series of articles here:

https://sportsscientists.com/2007/10/fluid-intake-dehydration-and-exercise-part-i-history-of-fluid-intake-and-a-conflict-of-interest/
Thank you very much for providing that link - well worth reading imo. Drink to thirst.
Deep in the 4th article is this (slightly edited):
"My sweat tastes salty

"Yes, it certainly does, and that is because it does contain some sodium. However it contains profoundly less [per volume] than the fluids in your body, and is still mostly water—body fluids have a sodium concentration of 140mM while sweat has a value of 20-60mM. Therefore when you remove a liter of sweat from your blood, it has much more of an effect on the volume compared to [an effect on] the solutes (sodium), and what happens is that the osmolality rises in response to sweat losses. This is absolutely crucial to realise – you cannot lose sodium, even if you are a “salty sweater”. If the sodium content of the blood is dropping, it’s because you’re drinking too much water [in extremis leading to hyponatremia - more dangerous than dehydration per se], not because you’re sweating sodium! In fact, a very interesting study was published in 1992 by Robert Cade (Gatorade). During a marathon 3 groups of runners were given Gatorade, or 1/2 Gatorade (half water, half Gatorade), or water. The really interesting finding was that the water group maintained their sodium concentration (a surrogate for the total osmolality) just fine, while the Gatorade group actually increased its concentration. This explains why people drink more of a sports drink compared to water—the sports drinks keep your osmolality higher and therefore makes you thirstier. So instead of lowering osmolality, which is what your body wants you to do, the sports drinks raise it. Seems kind of counter-intuitive, doesn’t it?"

I'm not altogether surprised; sports drinks always felt to 'strong' for me so I alternated them with water or had them half-strength.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Ajax Bay on June 04, 2019, 03:04:44 pm
All riders are individuals but I'll just put it out there one more time.

If you're thirsty, drink. Make sure you carry enough water to allow this, and to take care to fill up before running out. A small reduction from full hydration during exercise will have minimal adverse affect on performance. Loss of body weight after a serious ride is not a 'bad' sign and a decent few meals and a pint or two will see your lean mean athletic body back to its racing weight. Salty snacks are good because it encourages you to drink and replaces the small amount of sodium lost in sweat (see previous post). Take care not to drink too much. I did this once (trying to sooth an aching tooth over a bank holiday weekend) and started to develop some symptoms of (edited to) hyponatraemia (low sodium concentration in body fluids). Thankfully I realised what might be the cause of the symptoms and stopped swallowing the soothing cool water.

If, having already stripped to minimal cycle clothing and repeatedly wetted that clothing and ridden on, you're feeling uncomfortably hot, seek a cool place to rest, likely in the shade. Use water over clothing, especially in a hat, and body to cool. Streams are good (care with safety) and will be cooler than carried water and offer fluid convection. A regularly wetted 'neckerchief' is a good way of extracting/transferring energy out of the blood that flows to and from the brain near the neck skin/surface.
If you overheat (and these are the symptoms displayed by the OP - see his full description on the WCW thread) you may find drinking and eating cause nausea and this has a side effect of resulting dehyration because the subject is deterred from drinking. There's not a quick way back from that other than time in a cool place sipping water.. These symptoms are not caused by "dehydration" - it's heat 'exhaustion' which you don't want to develop into heat stroke. And just drinking more, with or without potions and powders, won't alleviate the symptoms.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: hellymedic on June 04, 2019, 03:11:16 pm
Please note

Hyponatraemia is low sodium concentration, dangerously associated with brain swelling and seizures. It is a feature of water intoxication.

Hyperntraemia is a high sodium concentration.

The two area easily confused!
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Cudzoziemiec on June 04, 2019, 03:23:13 pm
What even IS the evolutionary driver behind the whole - "Hey, we need to assimilate water and salt for the next few hours because it's freakin' hot, so let's commence a PUKE-A-THON!". Homo Sapiens - making zero sense, since 200k BC.
Presumably to make you stop whatever activity is overheating you, rest and cool down.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: madamemugwump on June 04, 2019, 03:32:44 pm
What even IS the evolutionary driver behind the whole - "Hey, we need to assimilate water and salt for the next few hours because it's freakin' hot, so let's commence a PUKE-A-THON!". Homo Sapiens - making zero sense, since 200k BC.
Presumably to make you stop whatever activity is overheating you, rest and cool down.

I'm glad someone had a stab at answering that question because I thought it a good one. Certainly, as a 'stop what you're doing RIGHT NOW' then puking is pretty successful. But as it also obviously dehydrates, it is a kinda curious response. Drastic times call for drastic measures?
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Kim on June 04, 2019, 03:35:52 pm
I assume it's just an evolutionary side effect of an overall beneficial response to poisonous foods.  "Ugh, my chemistry's out of whack!  EXPEL!  EXPEL!"
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Philip Whiteman on June 04, 2019, 03:36:29 pm
Dehydration through failure to keep hydrated after an audax can equally lead to severe problems.  Last year I was unfortunate enough to develop Rhabdomyolysis after riding an audax in temperature conditions of 29C.  Rhabdomyolysis is a rare condition in which muscle cells break down and release a substance into the blood that can lead to kidney failure and can be linked to deydration, heat stress and hard exercise.  Whilst hydrating during the ride, I failed to continue the regime after completing the brevet. Later that evening, I urinated a very dark brown and sedimented liquid which I quickly saved for specimen bottle which I delivered to a nearby hospital for analysis.  Kidney damage was avoided through a quick realisation of the cause and a decision to rapidly rehydrate with electrolytes.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: BeMoreMike on June 04, 2019, 03:42:39 pm
Phil, It was sad not to see you make it to Lilleshall on Saturday, when we heard you'd packed it was obvious something fairly serious had happened so good to hear it was nothing with any lasting damage and you're ok now.

I'm surprised more hasn't been mentioned on here about salt tablets;

https://www.wiggle.co.uk/saltstick-100-electrolyte-capsules

From what i've read they give you everything you need to combat sweat loses in a much more controlled and regulated dose than diluted drinks.

I've come to rely on them now and have stopped having any additives in my bottle, switching to just plain water with has been a revelation.
I used to love the flavoured electrolyte tabs, sugared carb powders and good old fashioned fruit squash, but realised it sometimes tasted too good, and was guzzling gallons of it which could leave me feeling bloated, constantly belching and farting and needing too many piss stops if i wasn't sweating ....amusing when solo riding but uncomfortable in a group !!

I've also changed my bike set up to only a single 1 litre bottle because there's never any issues with not having plain water to rinse myself, wet my cap etc. If i start a ride fully hydrated and guzzle as much fluids as possible at stops then i've found 1 litre on my bike has always been adequate. I also find it easier to rinse bottles and get top-ups if it's just plain water.


Before you go down the route of the changing your long standing bottle routine consider you don't necessarily need to balance your salt losses in your drinks.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: phil w on June 04, 2019, 04:53:16 pm
Phil, It was sad not to see you make it to Lilleshall on Saturday, when we heard you'd packed it was obvious something fairly serious had happened so good to hear it was nothing with any lasting damage and you're ok now.

Legs and appetite fully back Sunday afternoon.  Fatigue gone Monday afternoon. Resting heart rate back to normal this morning. So yes, all ok.  Will be out on recumbent tomorrow to see how things are.

I might just have to tape something in front of my recumbent seat and road bike stem, that says "Oi stupid, it's hot, what symptoms are developing, and what are you doing about it?"
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: hellymedic on June 04, 2019, 05:08:25 pm
You generally need to get VERY hot or badly crushed to have rhabdomyolysis.

Some medication might make this more likely; it can be a feature of Ecstasy abuse but I would hope you don't attempt to enhance your performance with amphetamines!.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: quixoticgeek on June 04, 2019, 05:26:50 pm
Phil, It was sad not to see you make it to Lilleshall on Saturday, when we heard you'd packed it was obvious something fairly serious had happened so good to hear it was nothing with any lasting damage and you're ok now.

I'm surprised more hasn't been mentioned on here about salt tablets;

https://www.wiggle.co.uk/saltstick-100-electrolyte-capsules

From what i've read they give you everything you need to combat sweat loses in a much more controlled and regulated dose than diluted drinks.


You have my attention. I find the flavour of most hydration tablets to be a bit meh. I tried the "neutral" flavour tabs, it was like drinking sea water. Sub optimal.

How do you find these tabs? It suggests one every hour, that would be 10-15 per day, which seems... Excessive. Any ideas on max dose per 24 hours ?

J
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: phil w on June 04, 2019, 05:31:08 pm
Thanks for suggestions so far.

Insanity is doing the same thing and expecting a different outcome as a certain scientist is quoted as saying. Number of different opposing opinions or shades of grey.

Apart from my Oi stupid message to go on the bike. I think I'm going to put down a checklist of escalating symptoms in hot weather, together with coping strategies. Then I'll take that on the rides. The arm cooler things have certainly caught my attention and appear to be a RAAM desert thing.  As have the salt tablets above as provides a way of seeing what difference it makes, without committing most of your water to it in one go.

As to water volume, reading the links and above posts I'm defo on the low side.  I'm guilty of not taking any water on rides up to three hours whatever the weather without ill effect. So I guess that leaked out onto the much longer rides in the heat where it matters. I've got used to riding through thirst when really I shouldn't.

As for it wasn't very hot.  Remember the temperature difference between shade and direct sunlight can be as much as 20C.  Shade makes a big difference else why rest in it?

Acclimatisation , defo. I spent a few months in Africa in 2001-2, in temps up to 46C in the shade, and was just fine. I did find it took about 3-5 weeks for my northern body to get get there though!

As to there may be no solution. Quite possible but I can't say I've explored anything like all the possible options.

Keep the opinions and experiences coming.

Staying annoyingly positive about hot weather strategy and tactics for my 400km+ rides under time limits.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Chris S on June 04, 2019, 05:46:07 pm
As to there may be no solution. Quite possible but I can't say I've explored anything like all the possible options.

There's loads of good ideas and info on this thread - it's great you have options to try, and I really hope you find a combination that works.  :thumbsup:
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Kim on June 04, 2019, 05:46:33 pm
Phil, It was sad not to see you make it to Lilleshall on Saturday, when we heard you'd packed it was obvious something fairly serious had happened so good to hear it was nothing with any lasting damage and you're ok now.

I'm surprised more hasn't been mentioned on here about salt tablets;

https://www.wiggle.co.uk/saltstick-100-electrolyte-capsules

From what i've read they give you everything you need to combat sweat loses in a much more controlled and regulated dose than diluted drinks.


You have my attention. I find the flavour of most hydration tablets to be a bit meh. I tried the "neutral" flavour tabs, it was like drinking sea water. Sub optimal.

How do you find these tabs? It suggests one every hour, that would be 10-15 per day, which seems... Excessive. Any ideas on max dose per 24 hours ?

Also interested, for exactly the same reason.  Generally I'm in favour of Real Food as a source of electrolytes during bike rides, but I used hydration tablets during the scorchio 3-hour race at the worlds last year, and it seemed to help, at least for the duration of the event.  My digestion rebelled immediately afterwards, thobut.

(Interestingly, my main problem there was that - as alluded to upthread - since the bottle was behind my back I had no idea how much I was actually drinking, or more importantly, how much was left.  Not really an audax problem, as you have enough time for knee breaks, so can audit your water supply then.)
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: jiberjaber on June 04, 2019, 06:46:36 pm
I can highly commend 'arm-coolers'  they work really well using your own sweat to generate the cooling effect whilst combining UV protection.  If you need extra cooling, then water from the bottle works well.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Philip Whiteman on June 04, 2019, 07:19:16 pm
You generally need to get VERY hot or badly crushed to have rhabdomyolysis.

Some medication might make this more likely; it can be a feature of Ecstasy abuse but I would hope you don't attempt to enhance your performance with amphetamines!.

Guess I was unlucky but that is what the blood tests and clinician's found.  As for the pharma, I was on Sertraline at the time and clinical research identifies a relationship between SSRIs and Rhabdo'. 
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: doctorafternoon on June 04, 2019, 07:22:09 pm
Very interested in this thread as a physiologist who studies such things. I think most of the sensible advice is here already. I'm a heavy sweater myself and use a combination electrolyte tablets and isotonic sport drinks (Lucozade sport usually). I also usually carry a bag of salted nuts, and eat savoury things at controls, but that's not always enough on its own.

Even knowing better, I got very ill myself last year and had my first DNF with similiar symptoms to Phil. It was a hot hilly 300 but after already doing two hot 600s a few weeks before and I got complacent and careless.

People vary a great deal. Those that sweat more usually have more of the type of body tissue (brown fat) that produces heat during muscle use. There's also a lot of variation in the salt composition of your sweat. So you have to find what works for you.

Dousing with water is definitely great when you get the chance. On the bonkers hot (mid 30s) West Highlands 1300 in 2014 there were beautiful little mini-waterfalls at the side of the road which were perfect, and probably saved me.

Hyponatraemia (low salt concentration) is the real big risk. Heat stroke or exhaustion symptoms are often confused with hyponatraemia, and of course they're often occuring together. The danger is that low salt can feel similar to thirst and then drinking just water will make it worse. Remember it's salt concentration that matters rather than absolute levels. And on a short timescale it's much easier for your body to deal with too much salt than too little, unless you have serious kidney issues.

Final tip is that dehydration can inhibit your appetite. Always worth having a good drink before the control and it'll be easier to eat.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Kim on June 04, 2019, 10:50:50 pm
Final tip is that dehydration can inhibit your appetite. Always worth having a good drink before the control and it'll be easier to eat.

Cycling inhibits my appetite, too.  I find milkshakey things (including ice cream) are quite good at rebooting it quickly, before consumption of proper food.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: bludger on June 04, 2019, 10:51:49 pm
The good thing about hot weather is that it gets the emergency soft cheese up to a perfect temperature in the jersey pocket ;D
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: BeMoreMike on June 05, 2019, 10:00:00 am

I'm surprised more hasn't been mentioned on here about salt tablets;

https://www.wiggle.co.uk/saltstick-100-electrolyte-capsules

From what i've read they give you everything you need to combat sweat loses in a much more controlled and regulated dose than diluted drinks.


You have my attention. I find the flavour of most hydration tablets to be a bit meh. I tried the "neutral" flavour tabs, it was like drinking sea water. Sub optimal.

How do you find these tabs? It suggests one every hour, that would be 10-15 per day, which seems... Excessive. Any ideas on max dose per 24 hours ?

J

i'd put that dosage recommendation alongside the "1 every 30 mins" on energy Gel wrappers. Could you imagine the state of your guts if you had say 15 on a 200km !! :sick:
 
Compared with other people i've ridden with and things i've read on here i wouldn't class myself as an an especially heavy sweater, and i'm not aware of me ever experiencing dehydration.

I try to only use those SaltStick tablets as a supplement, and will normally only need them in excessively hot weather. I'll usually only have 1 or 2 on a hot 200, i might have a maximum of 4 on day 2 of a hot 600.
I'm especially fond of salty snacks; every stop where i can refill by bottle i'll have at least 2 handfuls of salted peanuts which then enables me to guzzle a couple of pints of water before leaving with a full bottle.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: BeMoreMike on June 05, 2019, 10:02:35 am
The good thing about hot weather is that it gets the emergency soft cheese up to a perfect temperature in the jersey pocket ;D

After too many hot weather hours in the saddle i sometimes produce my own soft cheese !! :facepalm:
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: phil w on June 05, 2019, 10:37:12 am
Arm coolers and some of those salt stick tablets ordered.  Cue a snow forest for a couple of weekends time.  Recumbent out for a run later today.  I run a 2 litre bladder (behind the head) on the recumbent, so much easier to sip as I need to.  Going to get my Robinsons black currant flavourings again as well as I found they make the water more palatable on longer rides.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Cudzoziemiec on June 05, 2019, 10:38:57 am
I've never tried arm coolers, they might work well, but in the context of covering up being counterintuitive to cooling down, long clothes typical of Saharan regions were mentioned. It seems to me there are two big differences: Firstly, the clothes typically worn in Sahara, Arabian Peninsula, etc, are all-enveloping but also loose. They allow air to circulate inside them, over your skin. Almost the opposite of cycle clothing! This works to keep cool; I've ridden in India wearing kurta (long, loose cotton shirt worn there) and it definitely keeps you cool, but it's probably not ideal for long distance cycling: very un-aero for a start, and not good if it rains, though the pockets are useful.
The second difference is that desert regions are dry (of course) and a British summer can be hot but even if dry weather, the air is usually humid.
So I'm not saying arm coolers can't work, just questioning if the way in which they work is the same as desert robes.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: phil w on June 05, 2019, 10:48:10 am
Combination of SPF, the ones I have ordered are SPF 40+, so block 97-98% of UV rays from reaching the skin.  Secondly they wick excess moisture away from the skin, so the skin doesn't get overwhelmed by sweat, meaning the evaporative cooling can still occur, and rate of sweat reduces in response.  Thirdly you can soak them in water for further cooling if necessary. That's the theory anyway, and given the positive reviews I've read I haven't much to lose.  Worse case I have something I can use (instead of suncream) on the arms, with or without water soaking.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: hellymedic on June 05, 2019, 11:59:35 am
The relative humidity in the desert will be low, so there's more evaporative cooling but even on a muggy day RH is usually below 75% unless it's raining, which means sweat/water can evaporate and hot air can hold a LOT of water. Moving through the air will also increase evaporation.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: grams on June 05, 2019, 12:22:59 pm
As for it wasn't very hot.  Remember the temperature difference between shade and direct sunlight can be as much as 20C.  Shade makes a big difference else why rest in it?

23 C is not massively hot, even by British standards. I don't say that to downplay what happened to you - quite the opposite. Something very serious and unexpected happened. But I brought it up because it affects which advice is relevant.

("23 C" is the air temperature, which is important as it's how your body cools. On a windy day it will be much the same in the sun as in the shade)
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: phil w on June 05, 2019, 01:04:30 pm
As for it wasn't very hot.  Remember the temperature difference between shade and direct sunlight can be as much as 20C.  Shade makes a big difference else why rest in it?

23 C is not massively hot, even by British standards. I don't say that to downplay what happened to you - quite the opposite. Something very serious and unexpected happened. But I brought it up because it affects which advice is relevant.

("23 C" is the air temperature, which is important as it's how your body cools. On a windy day it will be much the same in the sun as in the shade)

Quote
Solar radiation can dramatically change the temperature of an object that it hits, heating it far above the actual air temperature. Jack Williams, former weather editor for "USA Today," stood outside in air that measured in the 20s Fahrenheit in the shade, but a thermometer in the sun behind him registered 80 degrees Fahrenheit. This is an extreme example of how solar radiation can cause areas in the sun to be warmer than those in the shade. Usually, the difference from the sun to shade will only be between 10 and 15 degrees Fahrenheit, says retired meteorologist Jim Lushine, in an interview with Florida's "Sun Sentinal."

Surprised you do not know the difference solar radiation can make to your temperature.  Being in direct sunlight really is not the same as shade when it comes to your temperature.

Every wondered why 11c at night feels colder than 11c in cloudy daylight or direct sun? - Solar radiation!


Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Von Broad on June 05, 2019, 01:50:38 pm
TrainerRoad podcast discussed sodium loading in episode 201 which I happened to listen to tonight. I’d take such ideas with a pinch of salt.

Very interesting, especially as Chad is talking about his own hydration strategies. It would seem there's a huge range of the amount of sodium we dump as individuals - something reflected in peoples experiences in this thread. Worth a listen.

This link should take you to the relevant few minutes on the subject.

https://www.youtube.com/watch?v=PSuH8q3EraM&t=3645s
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: phil w on June 05, 2019, 02:07:43 pm
TrainerRoad podcast discussed sodium loading in episode 201 which I happened to listen to tonight. I’d take such ideas with a pinch of salt.

Very interesting, especially as Chad is talking about his own hydration strategies. It would seem there's a huge range of the amount of sodium we dump as individuals - something reflected in peoples experiences in this thread. Worth a listen.

This link should take you to the relevant few minutes on the subject.

https://www.youtube.com/watch?v=PSuH8q3EraM&t=3645s

Thanks for the link, interesting. Salty sweaters losing as much as 8 times as much salt as light salty sweaters. Wow.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: duracellbunnyonabike on June 05, 2019, 05:00:27 pm
Interesting recent study about menthol and performance in the heat: http://www.mysportscience.com/single-post/2019/03/25/Can-peppermint-improve-performance-in-the-heat (http://www.mysportscience.com/single-post/2019/03/25/Can-peppermint-improve-performance-in-the-heat). Coincidentally I use HealthSpan Elite Kickstart Caffeine gum https://www.healthspan.co.uk/products/elite-kick-start-caffeine?sc_camp=460C2AB4214F46589003CB8E446B4CD0&gclid=CjwKCAjw0N3nBRBvEiwAHMwvNhjE6mOs2JbiMghWdW7Z6uGN9fECWbvCKedHkVRRUaKzh0N78JV3bhoCohkQAvD_BwE (https://www.healthspan.co.uk/products/elite-kick-start-caffeine?sc_camp=460C2AB4214F46589003CB8E446B4CD0&gclid=CjwKCAjw0N3nBRBvEiwAHMwvNhjE6mOs2JbiMghWdW7Z6uGN9fECWbvCKedHkVRRUaKzh0N78JV3bhoCohkQAvD_BwE) which is absorbed quicker and doesn't affect gut, but also gives a nice refreshing menthol flavour which might help with performance in the heat.

I am sponsored by Precision Hydration, so take my words with a pinch of salt if you want, but customised electrolyte intake based on my sweat rate (heavy!) and sodium loss per litre of sweat (high!) has definitely made a big difference in avoiding cramp issues (as well as not overdoing the effort in the heat).

Key is to be very careful and not add electrolyte tablets to carb drinks or drinks that already contain electrolytes. In an ideal world, you want to separate your solid and fluid intake, with fluid intake limited to just water (in which case use Precision Hydration salt tablets for sodium top up) or water with electrolytes and get your carbs from snacks/bars/gels and proper food at controls. https://www.precisionhydration.com/blogs/hydration_advice/how-does-precision-hydration-fit-in-with-your-nutrition-plan (https://www.precisionhydration.com/blogs/hydration_advice/how-does-precision-hydration-fit-in-with-your-nutrition-plan)

A telling graph about backing off the intensity during the hottest of the day, perfectly executed by Christophe Strasser during the 24hr in Borrego in 2016 (https://scontent.flhr1-1.fna.fbcdn.net/v/t31.0-8/15003468_1243462692377464_629658700051656289_o.jpg?_nc_cat=100&_nc_ht=scontent.flhr1-1.fna&oh=bed28fb380ec8537b50bf6841192b2f6&oe=5D563448)

As for effective cooling, I find ice socks work really well on hot days (bit of stocking filled with ice cubes and shoved in back of neck/top of jersey) plus ice cubes in water bottle. Cooling from the inside out.

There are lots of studies on heat acclimation but more relevant if riding somewhere outside of UK and preparing for a sudden heat shock. I have found hot baths and hot yoga quite useful in the past.

Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: hellymedic on June 05, 2019, 05:12:26 pm
There is upward of a litre of water attached to glycogen, which is likely to get released into the circulation at some point during a ride. You might find you are passing more water than you are drinking and might not be very thirsty as a result.
I often had this fairly late on a ride and had a penchant for Yazoo/Frijj at this point.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Chris S on June 05, 2019, 06:37:25 pm
Might that released water be excreted as sweat?

On a warm/hot all-day ride, I won't pee once from dawn 'til dusk, yet I can keep a sweat going. This may or may not be stressful on my kidneys - who knows? Given a bit of a run-up, I can handle pretty much all heat up to about 35c. We had to abandon a ride in France a couple of years back when it was 38/40; my HR was elevated all the time, so I was clearly stressed, and we thought it best to stop.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: hellymedic on June 05, 2019, 07:58:50 pm
The water is in the blood.
If your blood volume is increased the kidneys will put out excess water as urine.
If you are hot, you will sweat.

As I understand it, perspiration is only affected by hydration in severe dehydration.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: LittleWheelsandBig on June 05, 2019, 08:57:01 pm
Once the air temperature gets higher than body temperature, I tend to fall apart. Unless the humidity is very low (and sometimes not then), I just can't get rid of enough heat, particularly on a climb.

The worst was a 1000 brevet in Israel during an unseasonal heatwave. I was ok-ish on the flat and downhill but quite slow. Climbing up from the Dead Sea just after midday (= zero humidity), it was 47 degrees and I couldn't even walk the bike up an 8% grade in the sun. I had to lie down in the shade for a couple of hours while HK got over a nasty asthma attack, until the air temperature dropped about 10 degrees and we could get back on the bikes again.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: hellymedic on June 05, 2019, 09:34:34 pm
Mad dogs....

Once ambient temperature exceeds body temperature, you HAVE to lose heat and evaporation is the only route your body can do without external assistance; it's not much even in low humidity so it's easy to overwhelm the body's capacity, even at rest.

A resting man produces around 100W heat, a woman around 80W so folk can be nursed nude at 28C and stay in thermal balance.

Heat output will increase massively with any exertion - the energy in most of the food you eat will become HEAT...
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: CrazyEnglishTriathlete on June 05, 2019, 10:00:29 pm
I'm impressed by the volume of liquid that some people can drink.  The hottest UK 600 I did was the Denmead 600 back in 2005, where it was 32C on the second day.  If I tried to drink anywhere close to the recommended amount it would just pass straight through.  But then I sweat relatively lightly.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: GPS on June 06, 2019, 08:30:35 am
Yes - I had this problem on the Brimstone recently. I had a headache, my face looked like a tomato and my veins were more pronounced than normal, so I drank more because it was obvious I was de-hydrated. But my increased fluid intake just resulted in more frequent pee stops. It was most annoying ! It must've been helping to correct my de-hydrated state, but it didn't feel like it was having any effect.

I guess there's a finite rate at which the body can take in fluid to replenish what's been lost while you're still exercising. Once lost, you have to stop exercising and drink a lot to get back to being 'fully hydrated'  - whatever that actually means. I was still de-hydrated the next morning and wouldn't say I was back to normal (judging by urine colour) for about 24 hours.

One other note - I use a Craft cool mesh vest all year round now because in hot weather it gets slightly damp and has a cooling effect, whilst in winter it traps warm air next to the skin. The vest combined with 'Sportwool' jersey helps keep me cool in summer. I've also found that wearing a hat (under a helmet) all year round does the same thing - keeps my head warm in the winter and cool in the summer. (Although I shave my head, so hair doesn't complicate this ...)

But as everyone sweats differently who knows whether any of this would work for anyone else !
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: marylogic on June 06, 2019, 03:58:44 pm
Yes - I had this problem on the Brimstone recently. I had a headache, my face looked like a tomato and my veins were more pronounced than normal, so I drank more because it was obvious I was de-hydrated. But my increased fluid intake just resulted in more frequent pee stops. It was most annoying ! It must've been helping to correct my de-hydrated state, but it didn't feel like it was having any effect.



It sounds like the main problem was that you were hot/overheating rather than dehydrated, at least initially? If your veins were pronounced it suggests you were well hydrated, as does peeing frequently.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: GPS on June 06, 2019, 04:12:16 pm
Should've clarified - the headache started within 2 hours of starting the ride & I noticed the bulging veins and the tomato face in the early hours the next day when it was actually cooler.

I put it down to de-hydration starting early in the ride and not being resolved by drinking loads.

It really wasn't that hot - 23 deg C tops maybe ?


Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: phil w on June 06, 2019, 07:26:09 pm
Arm coolers have arrived. Nice to have a pair that fit, my arm warmers fall down these days.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Wycombewheeler on June 06, 2019, 07:45:59 pm
... so I drank more because it was obvious I was de-hydrated. But my increased fluid intake just resulted in more frequent pee stops. It was most annoying ! It must've been helping to correct my de-hydrated state, but it didn't feel like it was having any effect.

I guess there's a finite rate at which the body can take in fluid to replenish what's been lost ...
If you were peeing then your body had absorbed it. I'm not a medical professional but I'm sure there is no link from the digestive tract to the bladder.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Kim on June 06, 2019, 08:40:39 pm
... so I drank more because it was obvious I was de-hydrated. But my increased fluid intake just resulted in more frequent pee stops. It was most annoying ! It must've been helping to correct my de-hydrated state, but it didn't feel like it was having any effect.

I guess there's a finite rate at which the body can take in fluid to replenish what's been lost ...
If you were peeing then your body had absorbed it. I'm not a medical professional but I'm sure there is no link from the digestive tract to the bladder.

Indeed.  And when people talk about liquids "passing straight through" (which *is* an occupational hazard of drinking too much volume too quickly) that isn't actually what they mean...
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: hellymedic on June 06, 2019, 08:51:45 pm
Within reason, you will absorb all you drink. Beer lovers will take in many pints, most of which leave via the kidneys pdq.

Salt and food may help you retain some of your imbibed water.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Kim on June 06, 2019, 09:13:44 pm
TBH, the only times I've brought about diarrhoea by drinking too much too quickly have been by deliberately drinking excessive amounts in an attempt to defeat cystitis (gives you something else to think about for a bit while you're on the loo, innit), and that time I downed an entire litre of milk in the time it took to replace a mudguard bolt during a particularly hot bike ride...  :hand:
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Cudzoziemiec on June 06, 2019, 09:37:56 pm
A litre of milk in one go, particularly on a hot day...  :sick:
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: hellymedic on June 06, 2019, 10:13:58 pm
Milk is great for those who like it and can stomach it. It has a significant mineral content as well as its protein, carbs and fats.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: CrazyEnglishTriathlete on June 06, 2019, 10:26:59 pm
Milk is great for those who like it and can stomach it. It has a significant mineral content as well as its protein, carbs and fats.

Works for me.  The first time I finished the Kernow & SW I had some stomach problems on the second day (lots of descents in cold air, I think) and I got round on diary (milkshakes, ice creams) as that worked.  The temperature warmed up, max 27C, peaking around the time I had to battle the ultra-hilly section at the end.  I got to the finish fine and then immediately felt really weird.  Ian H was quite concerned and asked if I needed anything.  Instinct told me a packet of salt and vinegar crisps - which restored sanity really rapidly - as I'd not really taken any electrolytes in. (But I still find it easier to consume salts in solid food than in tablet - liquid form. 
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: phil w on June 06, 2019, 10:34:21 pm
If I have to use a McDs overnight on an X rated ride I will often have a milk shake or McFlurry instead of burger and chips which I can't really stomach later on. McFlurry takes longer to consume but powers me along for a fair period.

I usually don't like garage milkshakes as full of sugar but do like the Tesco thick strawberry milk shake. I ought to try ordinary milk on a ride as it won't be full of sugar.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Kim on June 07, 2019, 01:15:45 am
Milk is great for those who like it and can stomach it. It has a significant mineral content as well as its protein, carbs and fats.

Stomach yes, digest, not so much apparently.

I've noticed that Frijj has become less easily digestible (more inclined to slosh about in my stomach for hours, which isn't what you want on an audax) since they replaced much of the sugar with sweetener.  Supermarket 'flavoured milk' is much better, as it seems to consist mostly of milk, sugar, flavouring and colouring.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: CrazyEnglishTriathlete on June 07, 2019, 05:46:01 am
Milk is great for those who like it and can stomach it. It has a significant mineral content as well as its protein, carbs and fats.

Stomach yes, digest, not so much apparently.

I've noticed that Frijj has become less easily digestible (more inclined to slosh about in my stomach for hours, which isn't what you want on an audax) since they replaced much of the sugar with sweetener.  Supermarket 'flavoured milk' is much better, as it seems to consist mostly of milk, sugar, flavouring and colouring.


CET Junior doesn't digest aspartame, a common artificial sweetener very well.  For quite some time we avoided "no added sugar" products in the supermarkets - they are just as sweet as the ones they replace but have artificial sweeteners.  Without getting into the pros and cons of such subjects I try to avoid "no added sugar" products on Audax rides on the grounds that they've had a valuable source of calories taken out.  (Just the same as avoiding low salt products).  In fact, my Audax diet would probably be enough to give the food police a heart attack.  :smug: :smug: :smug:
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: GPS on June 07, 2019, 08:29:49 am
... so I drank more because it was obvious I was de-hydrated. But my increased fluid intake just resulted in more frequent pee stops. It was most annoying ! It must've been helping to correct my de-hydrated state, but it didn't feel like it was having any effect.

I guess there's a finite rate at which the body can take in fluid to replenish what's been lost ...
If you were peeing then your body had absorbed it. I'm not a medical professional but I'm sure there is no link from the digestive tract to the bladder.

Indeed.  And when people talk about liquids "passing straight through" (which *is* an occupational hazard of drinking too much volume too quickly) that isn't actually what they mean...

Well yes - there isn't a by-pass in there !

My point is that I was peeing more frequently, it was clear and I was still de-hydrated.  It must've been making a difference, but it didn't feel like it at the time and I still took 24 hours to get back to normal.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: LittleWheelsandBig on June 08, 2019, 10:04:21 am
You couldn't have been dehydrated if you were passing lots of clear urine. The main symptoms of dehydration are reduced urine output with darker colour. You were affected/ stressed by the conditions but not dehydrated.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Flatlander on June 08, 2019, 11:25:31 am
You couldn't have been dehydrated if you were passing lots of clear urine. The main symptoms of dehydration are reduced urine output with darker colour. You were affected/ stressed by the conditions but not dehydrated.

Possibly not completely true, depends on state of your blood. Too much glucose in it will cause urination even if its hydration is less than it should be. The same applies to excessive salt and other chemicals, C2H5OH and any other diuretic. Doing hard cycling, i.e. with high heart rate as in near an individuals max, these are unlikely becasue carbo absorption through the digestive system is limited with most ofthe blood going to the muscles and consumption of glucose by the muscles is high. For lower efforts with innappropriate eating and lower muscle use, a higher glucose level is possible if ones insulin systems are struggling.

With correct training or ample caffeine, low effort cycling can be powered largly by fat. We don't need to consume any extra fat on a short event like an Audax :-) Eating fat also restricts digestive speed but not a problem if riding at lower effort where carbs are not required.  I suspect using water or water with a small amount of salt if sweating hard would be best for hydration.

I find 80miles on just water(1L unless hot) is doable but am ready for the finish. I do this often as training. Sometimes the water has 30-50% fruit juice. The hunger bonk hits a few miles before the finish which is usefull for training for fat burning.
 
Mentally I require 1.5L with 30% fruit juice mix + ~5 muesli bars for a 200Km. If I eat too much I will piss more and need more fluid. If I eat too too much, normally a mental problem for me, I will start getting acid feeling in digestive system. When riding to a start I often end up going at max because I'm late, heart rate is 85% max for 1.5 to 3 hours(30-56 miles), I eat nothing during the ride out, drink only a few mouthfulls but arrive at the start in reasonably good condition. Here I believe I solve the mental "I want to eat syndrome" by worrying about the organiser may have dissappeared from the start by the time I arrive. I will have eaten some limited cereal or pasta and drunk coffee before departure.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: LittleWheelsandBig on June 08, 2019, 12:43:59 pm
The exceptions are just that. For most people and most instances, it is true.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: hellymedic on June 08, 2019, 02:43:17 pm
The issue is that water needs to be sufficient in all the body 'compartments' for optimal hydration and these compartments are not equal in any way.

Water is needed in the blood, in the cells of the tissues and between the cells of the tissues.

Having lots of water in the blood might not necessarily mean there is enough in the muscles.

Factors affecting water transfer can be complex.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: JulesP on July 30, 2019, 11:37:58 am
I read a long piece about heatstroke this morning. Takes its sweet time to get to the facts, but interesting nonetheless.

What It Feels Like to Die from Heat Stroke
 (https://www.outsideonline.com/2398105/heat-stroke-signs-symptoms)
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Wycombewheeler on July 30, 2019, 03:53:37 pm
Normally I dont have an issue with this, but last week with temperatures in the high 20s/low 30s. I found myself running out of water. I felt ok and ride was fine, but I'm sure o didn't drink enough.

With  PBP having 100km between controls, how much fluid should I be looking to carry. 2x750ml may only be enough for 2 hours if it is hot.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Ajax Bay on July 30, 2019, 04:28:05 pm
If it's hot, a proportion of the water available should go over your body, not down your neck. This is not a 'waste' of that water, however much we're conditioned to think of it in those terms. Heating up and below normal hydration levels both, above/below a threshold, incrementally adversely affect performance. Have a care not to over focus on the (perceived) dehydration which the sports drink industry has ramped up out of all proportion.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Alex B on July 30, 2019, 05:23:42 pm
If it's hot, a proportion of the water available should go over your body, not down your neck.

^^^This. This thread was a lifesaver (maybe even literally) on a ride over the Pyrénées during France's record-smashing heatwave last month (Tourmalet was 38°C at the bottom; 28°C at the top). As a sun-shy ginger, in previous rides I had withered when it got hot. But, with this thread in mind I started dumping water over me, instead of just drinking it. It made all the difference. Given adequate water supplies I'm now confident I can ride in pretty much any heat.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: hellymedic on July 30, 2019, 08:28:48 pm
Consider how you might dump heat without drinking/sweating. Wetting clothing is good and the water needn't be potable.

Immersing hands and feet in cold water is effective when you're not on the move.

Ice and ice-cream can absorb a little heat.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: quixoticgeek on July 30, 2019, 10:47:58 pm
Consider how you might dump heat without drinking/sweating. Wetting clothing is good and the water needn't be potable.

Immersing hands and feet in cold water is effective when you're not on the move.

Ice and ice-cream can absorb a little heat.

Have been stopping at water fountains along the road, soaking my cap, putting it back on under my helmet. Works really well. Found lots of water sources that look clean, but wasn't sure if drinking water. Works fine for cooling my cap.

Would work with arm warmers too...

J
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: bludger on July 30, 2019, 11:04:22 pm
During the worst of the heat last week I took to soaking a tea towel and wrapping it around my head like a Pharoah. While sticking my feet in a bucket filled with water and ice cubes. Recommended!
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Kim on July 30, 2019, 11:12:27 pm
At risk of stating the obvious, wet mitts are surprisingly cooling.  If you rinse them thoroughly when water is abundant it helps with pong-management, too.
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: Cudzoziemiec on July 31, 2019, 08:15:31 am
Difficult to ride with your feet in a bucket though!
Title: Re: Rehydration in Hot Weather on Audaxes.
Post by: hellymedic on July 31, 2019, 01:34:20 pm
Difficult to ride with your feet in a bucket though!

Indeed but paddling at some controls is possible.