Hot & Dry vs Hot & Humid

Hello Kenny:

I would have to say that I think it probably does take more
energy to stay cool at higher humidities than it does at
lower humidities with all other factors the same. When the
humidity is high the perspiration will not evaporate as
readily to cool the body. Therefore the body might actually
be warmer in the high humidity.

In the dry conditions the perspiration evaporates easily and
helps cool the skin better. This may lead to closer to
normal body temperatures.

Just make certain that whether you are in high humidity or
low that you drink enough fluids to keep hydrated.

Here in the area that I live a warm summer ride is in the
90's for both the humidity and the temperature. It would be
really nice to try riding where the humidity was a little
more moderate.

Al Butler

Quoted message said:

energy at the end of the rides. Does high humidity impact
the body's performance more that dry conditions at the
same temperature?

Absolutely! The key, in either high or low humidity, is to
keep yourself hydrated. I started my XC MTB ride in the 94
degree Florida heat at noon after drinking about 1/2
gallon of water... I had forgotten my Camelbak and I
didn't have a jersey or a bottle cage to hold a bottle. 2
hours later, I was fine!

--
Phil, Squid-in-Training

ZeeExSixAre said:

Quoted message said:

energy at the end of the rides. Does high humidity impact
the body's performance more that dry conditions at the
same temperature?

Absolutely! The key, in either high or low humidity, is to
keep yourself hydrated....

That is only half of what is needed. Water intake without
salt to replenish what is lost through perspiration can lead
to hyponatremia. Hyponatremia is one of the more unpleasant
things one can experience.

--
Tom Sherman – Quad City Area

Kenny Lee said:

Lately the weather has been hot and very humid. 36c with
90+ humidity. On this weekend's club rides I've felt like a
wet rag in need of disposal. I think it's the humidity
that's zapping my strength. When I do these same rides in
normal dry weather conditions I have a lot more energy at
the end of the rides. Does high humidity impact the body's
performance more that dry conditions at the same
temperature?

Yes.

See this chart:

crh.noaa.govheat.htmOpen ↗
--
Typoes are a feature, not a bug. Some gardening required to
reply via email. Surrealism is a pectinated ranzel.

Thanks all. Nice to know it's not all due to the aging
process.

Kenny Lee

Tom Sherman said:

ZeeExSixAre said:

Quoted message said:

energy at the end of the rides. Does high humidity
impact the body's performance more that dry conditions
at the same temperature?

Absolutely! The key, in either high or low humidity, is
to keep yourself hydrated....

That is only half of what is needed. Water intake without
salt to replenish what is lost through perspiration can
lead to hyponatremia. Hyponatremia is one of the more
unpleasant things one can experience.

Can you describe it further?

I complemented the water with fruit juices (apple, cran,
orange) and a banana, BTW.

--
Phil, Squid-in-Training

Quoted post said:

Originally posted by Kenny Lee
Lately the weather has been hot and very humid. 36c with 90+
humidity. On this weekend's club rides I've felt like a wet
rag in need of disposal. I think it's the humidity that's
zapping my strength. When I do these same rides in normal
dry weather conditions I have a lot more energy at the end
of the rides. Does high humidity impact the body's
performance more that dry conditions at the same
temperature?

Kenny Lee

High humidity also decreases the density of the air and wind resistance is lower with increasing humidity.

When its hot and humid, the lower density comes at a measurable price in partial pressure of oxygen. If its 90 F and 90% RH, even if you are at mean sea level, the density altitude your body feels is more like 5000 feet. For aircraft, these conditions are like 3000 feet of altitude but their engines can compensate for the lower partial pressure of oxygen since the EGT's will be lower. But human lungs canot compensate.

Water transfers heat far more efficiently than does dry air. This is why high humidity makes a hot day feel like a sauna, and makes a cold day feel absolutely frigid.

Because of this, the higher the humidity, the more you will *feel* the heat on a hot day. The more you feel the heat, the more you will sweat to compensate. The more you sweat, the more liquids you will need in a given period of time to replace it.

Also, the more liquids you need in a given period of time, the more you need to reduce the carbohydrate content of your sports drink to meter the volume of carbs per hour.

"Kenny Lee" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Lately the weather has been hot and very humid. 36c with
90+ humidity. On this weekend's club rides I've felt like
a wet rag in need of disposal. I think it's the humidity
that's zapping my strength. When I do these same rides in
normal dry weather conditions I have a lot more energy at
the end of the rides. Does high humidity impact the body's
performance more that dry conditions at the same
temperature?

Kenny Lee

When humidity is high, your body's cooling technique of
sweat evaporation is not as efficient. That is why you wind
up covered in sweat - the uptake of additional moisture in
humid air is more difficult. Here in the Arizona desert, we
think nothing of riding in temperatures over 100F but then
the humidity is, at this time of year, often in the single
digits. You sometimes wonder if you're actually sweating
because the sweat is evaporated so quickly. Then you see the
crusty salt deposits in your clothes and helmet. Many homes
and businesses in the southwest desert use "swamp coolers"
for cooling to save on electricity costs. These are simply
large fans blowing through wet pads; the outflowing air is
cool (and moister). Weather forecasts here typically also
include a guide for whether your swamp cooler will work well
or not. I think the dew point has to be below about 55F for
them to have much cooling capacity.

Quoted message said:

Here in the area that I live a warm summer ride is in the
90's for both the humidity and the temperature.

While the above is often stated it is practically impossible
to have 90+ humidity at the daily high temperature assuming
normal temperature variation between day and night. If the
nighttime low temperature is for example 68F with a 100%
humidity then assuming no weather change a daily high
temperature of
98.6F gives a humidity of 39%.

See hyperphysics.phy-hyperphysics.phy-Open ↗
astr.gsu.edu/hbase/kinetic/watvap.html#c1

Ted B said:

Water transfers heat far more efficiently than does dry
air. This is why high humidity makes a hot day feel like a
sauna, and makes a cold day feel absolutely frigid.

That's not why humid air feels hotter. It's because rates
of evaporation are lower in high humidity, or zero at 100%
humidity. You continue to sweat, but there is no
evaporative cooling.

The thermal conductivity of dry air is 50 times greater than
that of water vapor.
--
terry morse Palo Alto, CA bike.terrymorse.combike.terrymorse.comOpen ↗

"Ian S" wrote: (clip)You sometimes wonder if you're actually
sweating because the sweat is evaporated so quickly. Then
you see the crusty salt deposits in your clothes and helmet.
(clip) ^^^^^^^^^^^ Another clue is that you don't pee.

Weisse Luft said:

Kenny Lee said:

Lately the weather has been hot and very humid. 36c
with 90+ humidity. On this weekend's club rides I've
felt like a wet rag in need of disposal. I think it's
the humidity that's zapping my strength. When I do
these same rides in normal dry weather conditions I
have a lot more energy at the end of the rides. Does
high humidity impact the body's performance more that
dry conditions at the same temperature? Kenny Lee

High humidity also decreases the density of the air and
wind resistance is lower with increasing humidity.

When its hot and humid, the lower density comes at a
measurable price in partial pressure of oxygen. If its 90
F and 90% RH, even if you are at mean sea level, the
density altitude your body feels is more like 5000 feet.
For aircraft, these conditions are like 3000 feet of
altitude but their engines can compensate for the lower
partial pressure of oxygen since the EGT's will be lower.
But human lungs canot compensate.

In the portion of the lung where gas exchange occurs, the
air is always at
98.6F and 100% RH. In other words, the partial pressure of
water is always 47mmHg inside the lung, regardless of
what the weather is like outside.

ZeeExSixAre said:

Tom Sherman said:

ZeeExSixAre said:

>energy at the end of the rides. Does high humidity
>impact the body's performance more that dry conditions
>at the same temperature?

Absolutely! The key, in either high or low humidity, is
to keep yourself hydrated....

That is only half of what is needed. Water intake without
salt to replenish what is lost through perspiration can
lead to hyponatremia. Hyponatremia is one of the more
unpleasant things one can experience.

Can you describe it further?

I complemented the water with fruit juices (apple, cran,
orange) and a banana, BTW.

In my case I drank a lot of water at a rest stop on a 90+ F,
90%+ relative humidity day. About one-half hour later I
started suffering from a severe headache and general
disorientation. It was the one time that I have sagged in on
a ride, since I had enough mental function left to know it
would be really stupid to "prove" that I could tough out the
discomfort (especially after reading about all the athletes
who die from heat related illness).

--
Tom Sherman – Quad City Area

Jim Smith said:

In the portion of the lung where gas exchange occurs, the
air is always at
98.6F and 100% RH. In other words, the partial pressure of
water is always 47mmHg inside the lung, regardless of
what the weather is like outside.

Good point, but since total pressure changes with altitude,
so does the partial pressure of water vapor.
--
terry morse Palo Alto, CA bike.terrymorse.combike.terrymorse.comOpen ↗

Tom Sherman said:

In my case I drank a lot of water at a rest stop on a 90+
F, 90%+ relative humidity day. About one-half hour later I
started suffering from a severe headache and general
disorientation.

No matter how hot it is, don't drink more than about 24 oz.
of water per hour. But if you do end up drinking more than
that, be sure to take on extra electrolytes (which is a good
idea on a hot day, any way). Hyponatremia is not a good
thing to have. Stop immediately if you feel lightheaded or
queasy or get the dry chills.

Dehydration is far less dangerous than hyponatremia.

Pouring water over yourself on a hot ride will help cool you
down, but drinking extra water won't help and may be really
bad for you.
--
terry morse Palo Alto, CA bike.terrymorse.combike.terrymorse.comOpen ↗

Terry Morse said:

Jim Smith said:

In the portion of the lung where gas exchange occurs,
the air is always at
98.6F and 100% RH. In other words, the partial pressure
of water is always 47mmHg inside the lung, regardless
of what the weather is like outside.

Good point, but since total pressure changes with
altitude, so does the partial pressure of water vapor.

Actually, no. Because the air is saturated with water vapor
in the alveoli where gas exchange occurs, the partial
pressure of water is equal to the vapor pressure of water,
which is dependent only on temperature. Inside the lung the
partial pressure of water is always 47mmHg. It makes no
difference what the partial pressures of the other gases
present are. As altitude increases and total pressure goes
down, that 47mmHg does, of course, become a larger
percentage of the total. At sea level, for example, the
fraction of water vapor is 47/760 = .062 or about 6%, while
at the summit of Mount Everest the fraction is about
47/205 = 0.229 or 23% of the total.

Terry Morse said:

Tom Sherman said:

In my case I drank a lot of water at a rest stop on a 90+
F, 90%+ relative humidity day. About one-half hour later
I started suffering from a severe headache and general
disorientation.

No matter how hot it is, don't drink more than about 24
oz. of water per hour. But if you do end up drinking more
than that, be sure to take on extra electrolytes (which is
a good idea on a hot day, any way). Hyponatremia is not a
good thing to have. Stop immediately if you feel
lightheaded or queasy or get the dry chills.

I may have experienced that. I got light-headed, but only
when I stopped riding for 20 seconds or so (I usually ride a
brisk pace and am terribly out of breath when I stop) Does
this sound like hyponamentirenaeieia?

Other than sports drinks, what are some good, compact, cheap
sources of electrolytes?

--
Phil, Squid-in-Training

Ed said:

Quoted message said:

Here in the area that I live a warm summer ride is in the
90's for both the humidity and the temperature.

While the above is often stated it is practically
impossible to have 90+ humidity at the daily high
temperature assuming normal temperature variation between
day and night. If the nighttime low temperature is for
example 68F with a 100% humidity then assuming no weather
change a daily high temperature of
98.6F gives a humidity of 39%.

See hyperphysics.phy-hyperphysics.phy-Open ↗
astr.gsu.edu/hbase/kinetic/watvap.html#c1

Not this old canard again. Is there some reason the
physicists who put this [censored] up prevent water from
evaporating when the temperature rises above 68F? Is there
some reason the nighttime low will always be 68F or below?

Or is this the old, "Assume a spherical cow" gone to
meteorology? Email address works as is.