Author Topic: Rehydration in Hot Weather on Audaxes.  (Read 4666 times)

Re: Rehydration in Hot Weather on Audaxes.
« Reply #50 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.

CrazyEnglishTriathlete

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Re: Rehydration in Hot Weather on Audaxes.
« Reply #51 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.
Eddington Numbers 125 (imperial), 168 (metric) 518 (furlongs)  111 (nautical miles)

Re: Rehydration in Hot Weather on Audaxes.
« Reply #52 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.

Re: Rehydration in Hot Weather on Audaxes.
« Reply #53 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

hellymedic

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Re: Rehydration in Hot Weather on Audaxes.
« Reply #54 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.

Re: Rehydration in Hot Weather on Audaxes.
« Reply #55 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.

hellymedic

  • Just do it!
Re: Rehydration in Hot Weather on Audaxes.
« Reply #56 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!

Cudzoziemiec

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Re: Rehydration in Hot Weather on Audaxes.
« Reply #57 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.
"Pick a flower on Earth and you move the farthest star."

madamemugwump

Re: Rehydration in Hot Weather on Audaxes.
« Reply #58 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?

Kim

  • Timelord
Re: Rehydration in Hot Weather on Audaxes.
« Reply #59 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!"
Careful, Kim. Your sarcasm's showing...

Re: Rehydration in Hot Weather on Audaxes.
« Reply #60 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.
KIDDERMINSTER KILLER AND CLEE AUDAX, 20th July 2019; SOUTH SALOPIAN, 5th Oct 2019. http://beaconrcc.org.uk/audaxes/

BeMoreMike

  • Tries often, fails frequently.
Re: Rehydration in Hot Weather on Audaxes.
« Reply #61 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.

Re: Rehydration in Hot Weather on Audaxes.
« Reply #62 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?"

hellymedic

  • Just do it!
Re: Rehydration in Hot Weather on Audaxes.
« Reply #63 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!.

quixoticgeek

  • Mostly Harmless
Re: Rehydration in Hot Weather on Audaxes.
« Reply #64 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
--
Beer, bikes, and backpacking
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Re: Rehydration in Hot Weather on Audaxes.
« Reply #65 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.

Re: Rehydration in Hot Weather on Audaxes.
« Reply #66 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:

Kim

  • Timelord
Re: Rehydration in Hot Weather on Audaxes.
« Reply #67 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.)
Careful, Kim. Your sarcasm's showing...

jiberjaber

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Re: Rehydration in Hot Weather on Audaxes.
« Reply #68 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.
Regards,

Joergen

Re: Rehydration in Hot Weather on Audaxes.
« Reply #69 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'. 
KIDDERMINSTER KILLER AND CLEE AUDAX, 20th July 2019; SOUTH SALOPIAN, 5th Oct 2019. http://beaconrcc.org.uk/audaxes/

Re: Rehydration in Hot Weather on Audaxes.
« Reply #70 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.

Kim

  • Timelord
Re: Rehydration in Hot Weather on Audaxes.
« Reply #71 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.
Careful, Kim. Your sarcasm's showing...

bludger

  • Randonneur and bargain hunter
Re: Rehydration in Hot Weather on Audaxes.
« Reply #72 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
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BeMoreMike

  • Tries often, fails frequently.
Re: Rehydration in Hot Weather on Audaxes.
« Reply #73 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.

BeMoreMike

  • Tries often, fails frequently.
Re: Rehydration in Hot Weather on Audaxes.
« Reply #74 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: