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PSA - How hot is too hot?


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2 hours ago, throet said:

I'm starting to think this might be the best approach for me as well, with the exception of any trips that I can manage to take to ride in a more hospitable summer climate. Riding in Cali last week was simply amazing and I've had little desire to ride since returning. I wish I could get my wife to agree to just stay there in the summers, which my job would allow me to do. 

Like others on this thread, I have spent past summers trying to figure out what time of day is best to ride around here. Summer humidity here never goes away. It may feel less humid when you're baking in 98 degree temps, but the dew point late-afternoon / evening is usually only a couple of degrees lower than what it is early mornings. Our dew point here generally ranges from mid-sixties to low-seventies in the summer, which makes it very uncomfortable - period. Throw in temps in the high-nineties and it's downright oppressive. I used to believe that riding between 7-9 in the evening was best but have now concluded that the best time for me to ride is between 9-11 in the morning. Temps are still reasonable and just enough of the morning dew has burned off to keep my goggles from remaining in a constant fog.   

By the time the humidity burns off a bit it's usually too hot to ride. If you wait until evening or night the humidity is creeping back up by that time. I used to ride road when it would approach the mid nineties but you can manage your effort better on a road bike than on a MTB. On an MTB you're forced to put hard efforts in like it or not. You're also exposed to more air flow on a road bike than an MTB. 

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3 minutes ago, Chief said:

By the time the humidity burns off a bit it's usually too hot to ride. If you wait until evening or night the humidity is creeping back up by that time. I used to ride road when it would approach the mid nineties but you can manage your effort better on a road bike than on a MTB. On an MTB you're forced to put hard efforts in like it or not. You're also exposed to more air flow on a road bike than an MTB. 

^^^^This.

I also tend to flatten out my road rides more.

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Did a social ride with friends on the Drippings Springs/Onion Creek Loop last summer.  We were still about three or four miles from the car and I stopped and dipped my jersey in the creek, thinking the evaporative cooling would help a little with the heat for the last part of the ride.   It didn't do squat, because it was too damn hot and humid for anything to evaporate.  

So, that brings us to these facebook ads I've been getting for Arctic Cool Instant Cooling T shirts with, wait for it........HydrofreezeX cooling technology!   Their claims have to be complete hype, because  evaporative cooling only works within certain parameters of heat and humidity no matter what claims you make for HydrofreezeX technology. 

 

 

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8 hours ago, throet said:

I'm starting to think this might be the best approach for me as well, with the exception of any trips that I can manage to take to ride in a more hospitable summer climate. Riding in Cali last week was simply amazing and I've had little desire to ride since returning. I wish I could get my wife to agree to just stay there in the summers, which my job would allow me to do. 

Like others on this thread, I have spent past summers trying to figure out what time of day is best to ride around here. Summer humidity here never goes away. It may feel less humid when you're baking in 98 degree temps, but the dew point late-afternoon / evening is usually only a couple of degrees lower than what it is early mornings. Our dew point here generally ranges from mid-sixties to low-seventies in the summer, which makes it very uncomfortable - period. Throw in temps in the high-nineties and it's downright oppressive. I used to believe that riding between 7-9 in the evening was best but have now concluded that the best time for me to ride is between 9-11 in the morning. Temps are still reasonable and just enough of the morning dew has burned off to keep my goggles from remaining in a constant fog.   

I completely disagree. What doesn’t kill you makes you stronger. I plan to either be stronger. Today’s challenge was it was so humid that I had to ride without glasses. 

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I laughed yesterday at someone's Strava ride title, "It was wring out your SOCKS hot."  It really was, because by the end of my own ride I was thinking, "Why are my shoes feeling squishy? I didn't ride through a creek!"

Maybe I should be, but I'm not scared of the heat. I put two bladders in my pack because 100 oz isn't enough water sometimes. And I'll stop and not "push on" if I start to feel anything strange.

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23 hours ago, throet said:

I'm starting to think this might be the best approach for me as well, with the exception of any trips that I can manage to take to ride in a more hospitable summer climate. Riding in Cali last week was simply amazing and I've had little desire to ride since returning. 

That's the rub for me.  Lived in too many places that aren't this hot during the summer and still a bit spoiled.

Mountain biking is something i do for fun and riding when its absolutely miserable is not that. If its a matter of staying fit, i'll take the gym any day over 100* , 5mph switchback/ledge trails that i have ridden countless times when its not miserable. My problem is, when something becomes un-fun, i usually stop doing it. Happened with auto racing & off roading and i don't want that to happen with MTB.

On the travel tip: We're gonna do a MT Lemmon run in a couple of weeks and will have my BIL shuttle us to the top like bitches🤣

 

On the heat tip:  When i used to head out for early morning summer rides id wear a pair of lightweight running shorts and use triathlon briefs with chamois under it. Not the sexiest thing on earth but god damn, so much lighter & cooler than baggies and no spandex required.

https://www.lightinthebox.com/en/p/mubodo-men-s-cycling-under-shorts-bike-briefs-sports-blue-mountain-bike-mtb-road-bike-cycling-clothing-apparel-bike-wear-micro-elastic_p7263190.html

 

Edited by ATXZJ
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2 hours ago, The Tip said:

And I'll stop and not "push on" if I start to feel anything strange.

Beware of that thinking. Many have died before they picked up on their bodies signals. Dehydration and heat stroke will sneak up on you like Mittens🐍

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10 minutes ago, Chief said:

Beware of that thinking. Many have died before they picked up on their bodies signals. Dehydration and heat stroke will sneak up on you like Mittens🐍

Had a 33 y/o buddy who thinks he's superman blackout from heat coming down dead horse in moab. Came >< that close to dying that day.

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On 6/21/2019 at 11:28 AM, Ridenfool said:

Heat moves in three ways,

  Radiation (i.e. sun shining on skin surface),

  Convection (i.e. heat carried between air and skin, or, between sweat and air), and

  Conduction (i.e. direct contact with a heat sink, such as when sweat moves from pore to skin carrying heat with it, or when cool water is poured directly on the skin, and when you jump in the lake).

Sweating uses conduction and convection to cool the body. The heat is moved from inside the body to the skin surface by conduction of heat into the sweat, then, further cooling relies on convection to evaporate the heated water into the air. Technical clothing can help move the water from skin to air more efficiently, as well as reduce reverse convection between heated air and exposed skin and block radiated heat from infrared sources like the sun.

93 degree F is a break-over point where the air becomes a more significant hindrance to the cooling process. Above this point a person is operating at the edge of the envelope where cooling system performance falls off at a steeper rate as the temperature increases.

This temp can be a useful reference for folks to judge when to significantly increase water intake, and reduce those paths that may bring heat into the body. All contribute to keep the heat moving in the right direction. Plus, being more attentive to the signs of heat-related symptoms is more critical.

 

there are other mechanisms like phase transition which is also evaporation.  It is conduction from direct contact of your skin with sweat and then a phase change of the sweat from water to water vapor.

https://en.wikipedia.org/wiki/Heat_transfer#Advection

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3 hours ago, crazyt said:

there are other mechanisms like phase transition which is also evaporation.  It is conduction from direct contact of your skin with sweat and then a phase change of the sweat from water to water vapor.

https://en.wikipedia.org/wiki/Heat_transfer#Advection

The Wiki doesn't really say whether there is any effect upon the transfer of heat during the phase transition. If the same amount of heat exists, only spread out over the greater area the vapor occupies that would not really change anything. It seems to me that convection of the evaporated water is what moves the heat away from the body.

If there is a component of the phase transition from water to water vapor that makes some significant difference in how the heat moves away from the skin I'd be curious to know about that.

If heat loss is slowed to make this phase change happen that would be interesting. Likewise, if heat loss speeds up in the process of changing from water to vapor that too would be good to know more about. If the the phase transition has little to no effect on a body getting rid of heat, that would be less interesting.

 

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On 6/22/2019 at 6:20 PM, AustinBike said:

What doesn’t kill you makes you stronger.

Not true when it comes to heat. Heat stroke and even heat exhaustion can have long-lasting ill effects on your body. There are plenty of ways to stay strong during the summer without risking heat-related illness. But hey, if you actually enjoy riding in the sweltering heat - have at it. For me, it's just not fun. 

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10 hours ago, throet said:

Heat stroke and even heat exhaustion can have long-lasting ill effects on your body. 

Indeed - you get heat stroke even once, you may never be the same again. It's certainly not likely to make you stronger. I make sure I avoid it, which isn't too hard.

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2 hours ago, TAF said:

Indeed - you get heat stroke even once, you may never be the same again. It's certainly not likely to make you stronger. I make sure I avoid it, which isn't too hard.

very true...I had severe heat stroke about 4 years ago and it still affects me to this day.

Don't fucking do it

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14 hours ago, Ridenfool said:

The Wiki doesn't really say whether there is any effect upon the transfer of heat during the phase transition. If the same amount of heat exists, only spread out over the greater area the vapor occupies that would not really change anything. It seems to me that convection of the evaporated water is what moves the heat away from the body.

If there is a component of the phase transition from water to water vapor that makes some significant difference in how the heat moves away from the skin I'd be curious to know about that.

If heat loss is slowed to make this phase change happen that would be interesting. Likewise, if heat loss speeds up in the process of changing from water to vapor that too would be good to know more about. If the the phase transition has little to no effect on a body getting rid of heat, that would be less interesting.

 

Phase change is an extremely efficient method of heat transfer. That is why large air conditioners use cooling towers (evaporate water to cool it) instead of the smaller units (residential) air to air heat exchangers. In an ideal world (read - does not happen in the real world), getting your jersey wet by any means would get the jersey temperature down to the "wet bulb temperature" which is just slightly above the dew point temperature. Adding salt from sweat raises the temperature just a bit (couple of degrees) so you will never reach the wet bulb temperature. As water continues to evaporate the jersey temperature will stay locked at that temperature heat transfer coefficient is improved by a factor of 10's to 1000's. So phase change is EXTREMELY helpful in lowering body temperature.

But as said above - if the wet bulb temperature is already too warm and at best you can get down to the wet bulb temperature - you are not cooling off.

A couple of other notes from an engineer who deals with these data as part of his job. The absolute moisture content in the air (also known as "dew point temperature" by those of us who like talking whole numbers like 65F to 75F instead of decimals like 0.001 to 0.1), really does not change during a 'typical day'. Unless a front blows thru or there is a rain event, the dew point temperature will be about +/- 2F all day. If you don't have anything else to go by, the low temperature of a summer day will be close to the dew point temperature in Central Texas.

Now back to MTB. I prefer to do night rides during the heat of the summer. Early morning rides may get me a slightly cooler temperature but it also gets me a constant stream of spider webs across the face. My vision seems to like the transition from some daylight to nothing but lights better than the 'nothing but lights' to dawn transition. But I also ride early mornings when that is what the group wants to ride. But now days I mostly ride alone so I pick nights.

ETA - info on wet bulb, dry bulb and dew point temperatures is at - https://www.engineeringtoolbox.com/dry-wet-bulb-dew-point-air-d_682.html

 

Edited by cxagent
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From what I gather, based on the info cxagent posted, phase transition is very efficient at moving the heat in the water between the liquid and vapor states. Then, once vapor is formed, convection is what moves the heat on into the air and away from the skin.

If I were to visualize "phase change" as a part of the movement of heat it would look like a layer or a step in the process.

Example: Sweat absorbs heat from body, pores move sweat to skin surface, phase transition changes heat in liquid to heat in vapor, convection moves the vapor into the surrounding air, carrying heat away from the skin.

Phase Transition is like a part of the path, much like the thermally conductive compound between CPU and Heat Sink is a layer the heat must efficiently move through before being carried off by convection from air passing over the fins of the Heat Sink.

The wet bulb effect is interesting. This essentially determines the maximum potential cooling that could be achieved under perfect conditions. So, if 82 is the daily low (wet bulb/dew point), and the OAT is 94, under routine conditions with reduced (lets use 50%) efficiency there may only be 5 or 6 degrees of cooling, at best.

If the OAT is 100 with an overnight low of 85 the cooling effect might only be just approaching that 93 degree F point where no actual cooling of the skin occurs. (change the numbers based upon whatever the realistic percentage of cooling under these conditions might be)

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