Author Topic: Rehydration in Hot Weather on Audaxes.  (Read 5331 times)

Re: Rehydration in Hot Weather on Audaxes.
« Reply #75 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.
If you don’t make time for exercise now, sooner or later you’ll need to make time for ill health.

Cudzoziemiec

  • Waking up now, put the kettle on!
Re: Rehydration in Hot Weather on Audaxes.
« Reply #76 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.
I do not ride a great big Mercian, gangster tanwalls, fixed cog in the back.

Re: Rehydration in Hot Weather on Audaxes.
« Reply #77 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.
If you don’t make time for exercise now, sooner or later you’ll need to make time for ill health.

hellymedic

  • Just do it!
Re: Rehydration in Hot Weather on Audaxes.
« Reply #78 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.

Re: Rehydration in Hot Weather on Audaxes.
« Reply #79 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)

Re: Rehydration in Hot Weather on Audaxes.
« Reply #80 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!


If you don’t make time for exercise now, sooner or later you’ll need to make time for ill health.

Re: Rehydration in Hot Weather on Audaxes.
« Reply #81 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
Garry Broad

Re: Rehydration in Hot Weather on Audaxes.
« Reply #82 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.
If you don’t make time for exercise now, sooner or later you’ll need to make time for ill health.

Re: Rehydration in Hot Weather on Audaxes.
« Reply #83 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. Coincidentally I use HealthSpan Elite Kickstart Caffeine gum 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

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

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.


hellymedic

  • Just do it!
Re: Rehydration in Hot Weather on Audaxes.
« Reply #84 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.

Re: Rehydration in Hot Weather on Audaxes.
« Reply #85 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.

hellymedic

  • Just do it!
Re: Rehydration in Hot Weather on Audaxes.
« Reply #86 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.

LittleWheelsandBig

  • Whimsy Rider
Re: Rehydration in Hot Weather on Audaxes.
« Reply #87 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.
Wheel meet again, don't know where, don't know when...

hellymedic

  • Just do it!
Re: Rehydration in Hot Weather on Audaxes.
« Reply #88 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...

CrazyEnglishTriathlete

  • Miles eaten don't satisfy hunger
  • Chartered accountant in 5 different decades
    • CET Ride Reports and Blogs
Re: Rehydration in Hot Weather on Audaxes.
« Reply #89 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.
Eddington Numbers 125 (imperial), 170 (metric) 520 (furlongs)  112 (nautical miles)

Re: Rehydration in Hot Weather on Audaxes.
« Reply #90 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 !

Re: Rehydration in Hot Weather on Audaxes.
« Reply #91 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.
Audax Ecosse - always going too far

Re: Rehydration in Hot Weather on Audaxes.
« Reply #92 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 ?



Re: Rehydration in Hot Weather on Audaxes.
« Reply #93 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.
If you don’t make time for exercise now, sooner or later you’ll need to make time for ill health.

Re: Rehydration in Hot Weather on Audaxes.
« Reply #94 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.
   Eddington  87 miles

Kim

  • Timelord
Re: Rehydration in Hot Weather on Audaxes.
« Reply #95 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...
Careful, Kim. Your sarcasm's showing...

hellymedic

  • Just do it!
Re: Rehydration in Hot Weather on Audaxes.
« Reply #96 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.

Kim

  • Timelord
Re: Rehydration in Hot Weather on Audaxes.
« Reply #97 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:
Careful, Kim. Your sarcasm's showing...

Cudzoziemiec

  • Waking up now, put the kettle on!
Re: Rehydration in Hot Weather on Audaxes.
« Reply #98 on: June 06, 2019, 09:37:56 pm »
A litre of milk in one go, particularly on a hot day...  :sick:
I do not ride a great big Mercian, gangster tanwalls, fixed cog in the back.

hellymedic

  • Just do it!
Re: Rehydration in Hot Weather on Audaxes.
« Reply #99 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.