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PSA - How hot is too hot?


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https://www.fix.com/blog/motorcycle-riding-in-hot-weather/

Studies have shown that when the air temperature is above 93 degrees F there is no longer a "wind chill" effect to keep the body cool, and the air will actually be transferring heat to the body, instead of the other way round.

For motorcyclists, and likely mountain bikers as well, the most viable solution is to add layers to prevent hot air from making direct skin contact. This is counter-intuitive, and when involved in more athletic pursuits it will still be only marginally helpful to wear long sleeves, wet neck wraps, pour water on head and clothing, and those sorts of techniques to enhance cooling.

Water requirements internally and externally go up drastically when temps are above 93F and the duration of any ride may need to be reduced to avoid heat-related stress and the severe health issues that can come with it.

Be cool, and happy trails!

 

Edited by Ridenfool
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Most of the cooling in humans is not convective though, it's evaporative. (Dogs only have convective cooling, except for through their mouths, so keep your dogs home in this heat--especially the brachycephalic (pugs, bulldogs, boxers, etc.).)  One of the things I remember the most about HS Chemistry was the experiment to measure calories for evaporation vs convection.  Basically, it was measuring how much heat you could extract by adding ice, vs evaporating.  It wasn't even close!

Layers that promote evaporation make a difference as well.  The key is to make sure you're sweating.  Once you stop sweating they act like warmers.  If it's extremely humid where water doesn't evaporate, then that's a problem as well.  For me, I can ride in the dry heat better than in cooler more humid temps, as long as I have plenty of fluids.  I'll ride in the afternoon rather than in the morning for this reason.

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Hmmmm....I can't really comment much from the science behind riding in the heat and such.  But I do know that I tolerate the heat very well and actually prefer the warmth over the cold.  That said, being Keto means that physiologically I don't naturally carry as much water weight along with me.  (Carbs and water are linked, when one goes, so does the other)  All of that means that I have to be diligent with my daily and riding water/hydration consumption.  But as long as that is happening, then I find I can regularly ride fine through our summer heat.  I do find road riding a bit of an advantage here because the increased speeds mean that I get the passive cooling from the breeze.  Its very noticeable when I stop at stoplights during my commute.  The heat radiating off the asphalt (when stopped) is oppressive.  But not so much when consistently moving.  I also get solid satisfaction out of knowing that when all the "softies" are home soaking up the cool A/C....I'm out working on my hard-man status riding in the heat.  💪

Later, -CJB

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3 minutes ago, CBaron said:

I do find road riding a bit of an advantage here because the increased speeds mean that I get the passive cooling from the breeze.  Its very noticeable when I stop at stoplights during my commute.  The heat radiating off the asphalt (when stopped) is oppressive.  But not so much when consistently moving.  

+1.  Also on steep climbs or when you have a tailwind!  Feels like my shoes will melt.  I love the headwinds in the summer.

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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.

 

Edited by Ridenfool
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1 hour ago, AntonioGG said:

Most of the cooling in humans is not convective though, it's evaporative. (Dogs only have convective cooling, except for through their mouths, so keep your dogs home in this heat--especially the brachycephalic (pugs, bulldogs, boxers, etc.).)  One of the things I remember the most about HS Chemistry was the experiment to measure calories for evaporation vs convection.  Basically, it was measuring how much heat you could extract by adding ice, vs evaporating.  It wasn't even close!

Layers that promote evaporation make a difference as well.  The key is to make sure you're sweating.  Once you stop sweating they act like warmers.  If it's extremely humid where water doesn't evaporate, then that's a problem as well.  For me, I can ride in the dry heat better than in cooler more humid temps, as long as I have plenty of fluids.  I'll ride in the afternoon rather than in the morning for this reason.

Yeah, I really suffer in the 80s-90s when it's humid, especially on MTB rides.  I'm better off in the 90s-100s when it's just hot.   

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1 hour ago, AntonioGG said:

Most of the cooling in humans is not convective though, it's evaporative. (Dogs only have convective cooling, except for through their mouths, so keep your dogs home in this heat--especially the brachycephalic (pugs, bulldogs, boxers, etc.).)  One of the things I remember the most about HS Chemistry was the experiment to measure calories for evaporation vs convection.  Basically, it was measuring how much heat you could extract by adding ice, vs evaporating.  It wasn't even close!

Layers that promote evaporation make a difference as well.  The key is to make sure you're sweating.  Once you stop sweating they act like warmers.  If it's extremely humid where water doesn't evaporate, then that's a problem as well.  For me, I can ride in the dry heat better than in cooler more humid temps, as long as I have plenty of fluids.  I'll ride in the afternoon rather than in the morning for this reason.

Yeah, humid mornings are awful. Afternoons are HOT, but at least the humidity is much lower.

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1 hour ago, CBaron said:

I also get solid satisfaction out of knowing that when all the "softies" are home soaking up the cool A/C....I'm out working on my hard-man status riding in the heat.

Same for me. But in the cold too. 

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Tip - you should always ride.

My record is the Greenbelt at 110 (the temperature, not some index.) On the other end of the spectrum it is probably around -20F back in Chicago.

It is all about dressing appropriately, hydrating and riding to the temps. At 110 I took it slow.

I do believe that there are smarter people than me on this, but I'd rather die of heatstroke from riding than from heart disease from not riding.

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I never meant this thread to infer it is ever too hot to ride. Just wanted to illustrate the tipping point where a higher degree of awareness would be prudent.

I've had to deal with a friend succumbing to heat and passing out while ten miles into a Rocky Hill ride. Scared us both. It was 106 that day.

Not exactly the point to be coming up to speed on these facts. Better to know before putting foot to pedal.

Tis the season.

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2 hours ago, Ridenfool said:

 

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.

 

 

Its interesting that you say this.  Because just last week I was digging through my own Strava archives and ran across one from last summer.  In my notes I had stated that the outside temps of 91* almost felt cool considering the (then) recent temps of 98*.  I opined about how much different 6-7* made in my perceptions.  Come to find out....there was some science involved in my perceptions. 

-CJB

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2 minutes ago, CBaron said:

 

Its interesting that you say this.  Because just last week I was digging through my own Strava archives and ran across one from last summer.  In my notes I had stated that the outside temps of 91* almost felt cool considering the (then) recent temps of 98*.  I opined about how much different 6-7* made in my perceptions.  Come to find out....there was some science involved in my perceptions. 

-CJB

Hey, maybe you're not such a luddite after all!

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Gotta ride down to pick up my truck from service today and thinking it might be a good idea to stop by the snowcone place on the way!  It was super humid this morning when I rode to work, but seems like that's burned off a little and is just plain hot now.

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40 minutes ago, Anita Handle said:

Without rectal temp data transposed against power and heart rate, these heat performance claims are all just anecdotal bullcheeze. ☀️

Do you know how to tell the difference between an oral thermometer and a rectal thermometer?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The taste.

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I have to admit that Rocky Hill for some reason feels extra hot to me compared to almost any other trail.  I don't know what it is...maybe those red pebbles or something.  I've ridden there at 99°F and it felt awful!

CJB, I agree.  To me, by August (and even now already this year) 92°F feels cool to me, especially in the afternoons.

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17 hours ago, ATXZJ said:

Riding season ends for me in may. Unless I'm loading up and getting TF outta this swamp, I'm gym only.

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.   

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