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Faster in Hot, Humid Weather?

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Faster in Hot, Humid Weather?

Old 07-08-10, 09:49 AM
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Daytrip
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Faster in Hot, Humid Weather?

Maybe I'm just getting stronger (finally), but I've had some really fast rides recently in this hot, humid weather. Maybe it's the lack of wind, but it just feels like there's less resistance on all fronts.

You'd think the opposite. You'd think your body would slow down in the heat and humidity. You'd think your tires would get soft and slow down on the soft road surface. You'd think that the humidity would make the air heavier and thus create more friction.

That's the trouble with thinking.

Anybody else notice this?
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Old 07-08-10, 09:54 AM
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The warmer air is less dense and provides less resistence.

More humid increases resistence, but the effect is small and trumped by temperature.

https://www.analyticcycling.com/Force...sity_Page.html

At sea level, for an average sized rider, and power out put of 250 watts, the difference is about .3mph on flat ground going from 75 degrees F to 95 degrees F.
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Old 07-08-10, 10:00 AM
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i've been getting faster too but i don't think about it much. i just tell everyone whether they want to hear it or not.
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Old 07-08-10, 01:54 PM
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We don't do humid here in Nevada, but I've always enjoyed riding in hot weather, and when I used to keep track of my speed, I was a little faster when it was 90-95 (that's Northern Nevada hot. Southern Nevada hot is 110+, and I don't know how fast i go then because I stay home...).
I dunno about air density. I doubt I go fast enough that it matter
I
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Old 07-08-10, 02:04 PM
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smaller riders have better heat exchange properties than larger riders. (volume:surface area)
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Old 07-08-10, 02:06 PM
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I just tend to ride faster because I want to get out of the heat and back into my house.
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Old 07-08-10, 02:10 PM
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Originally Posted by merlinextraligh View Post
The warmer air is less dense and provides less resistence.

More humid increases resistence, but the effect is small and trumped by temperature.

https://www.analyticcycling.com/Force...sity_Page.html

At sea level, for an average sized rider, and power out put of 250 watts, the difference is about .3mph on flat ground going from 75 degrees F to 95 degrees F.
Interesting. I didn't think the difference would be that big.

Just read something on Slowtwitch the other day though about heat and power. They said Coggan's work showed about 3% decrease in wattage for every 10*F the heat index was over 60*F. I think this was measured for just one rider though, not a large sample of people. So from 75 to 95 would see a 6% decrease in power, which would probably more than cancel out the air density effects.
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Old 07-08-10, 02:18 PM
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Originally Posted by merlinextraligh View Post
More humid increases resistence, ...
Why? Water is less dense than nitrogen or oxygen.
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Old 07-08-10, 02:23 PM
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Originally Posted by asgelle View Post
Why? Water is less dense than nitrogen or oxygen.
The guys at Analyticcycling say the effect of water vapor is small enough to be ignored in their calculations. I was assuming the effect of more water vapor would be more resistence not less, but its an assumption.

Edit: and apparently my assumption is wrong, humid air is surprisingly, at least to me, less dense:

https://www.usatoday.com/weather/wdensity.htm

but again, my point for this discussion was that the lower density of warm air is in fact enough to affect speed.
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Old 07-08-10, 02:24 PM
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No. I detest riding in humidity. Hence the reason I live in an arid area.
Over 90F I tend to slow down a fair amount. 65-75 being my sweet spot.
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Old 07-08-10, 02:26 PM
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Moisture is also necessary to exchange oxygen in your lungs. Hard breathing in dry conditions can dry out the inside of your lungs to the point where moisture is limiting the amount of oxygen dissolving into the blood stream.
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Old 07-08-10, 02:36 PM
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Virtually all my rides start with 5 miles of climbing--700 feet to be exact, so I do notice the heat and humidity by the excessive amount of sweat pouring off my body when I stop. I don't notice that it takes any toll at all on my cardiovascular performance. So I'm inclined to think that Dan The Man is making a valid point. As long as I stay hydrated, I'm good to go in the heat.
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Old 07-08-10, 04:10 PM
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It seems like I go faster in the heat, but I sure don't last as long.

I had planned on doing a 50-mile ride today, but cut it short 13-14 miles out when I noted my heart rate staying really close to threshold despite going down a long 1-2% grade and pretty much coasting. My HR was staying up above 150 when normally it would have been well below 140, maybe even below 130. Given that and the heat, the sun, and the humidity, I turned around and went home. The first 10-12 miles had felt great, if extra hot, and I was going along a bit faster than normal. Then my heart rate started creeping up. It started back down after about 5 minutes of 10-12 MPH riding, then was fine the rest of the way home, but I didn't really push very hard.

I guess I came close to heat stroke, as I think an elevated heart rate is one symptom.
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Old 07-08-10, 04:35 PM
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Funny, my rides today and yesterday were in this afternoon heat and terrible humidity and I felt great. Not sure if I was faster but I was surprised...
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Old 07-08-10, 06:02 PM
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I was out for 40 miles Wednesday in the heat of Illinois and did ok. My pace was a little better than average given I ran 4 miles before the bike ride. I manage to average 19mph in the basic flats of Illinois. I went through 2 bottles of water in 90 minutes and then on empty the last 30 minutes or so could have used more. I find the heat ok seems like it is worse but the stats do not say it is.
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Old 07-08-10, 07:34 PM
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Be careful not to confuse "correlation" with "causal". In other words, some things may be related but coincidental. A popular example at school is to point out that the more churches there are in an area, the more crime there is. Do churches cause crime? Not necessarily. However, having more people means that the overall crime rate goes up. 10 million people in NYC have more crime than the 1000 people that live in my "village" (I learned last night that it's a "village" and not even a "town"). I daresay there are more than 2 churches in NYC, which is how many we have in town. Our crime rate is pretty low.

So, does hot and humid weather increase performance?

Not for me.

BUT...

By May or June I've been riding for many months, focusing on getting stronger, racing weekly if possible, more than once a week if I can. Therefore, I am way more fit. I've done, I dunno, maybe 20 races? A bunch of group rides where I make extreme efforts. I'm way more fit than, say, I was in December.

Being fit makes me ride faster. Heat and humidity, in excess amounts, slow me down.

So my average speeds are up on my training rides (JRA rides mainly, where I just ride as I feel like riding), substantially.

But relative to other riders, I think I ride better when it's cooler out.

If nothing happens to me, I'll be even faster this fall, when it's cooler and less humid.

cdr
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Old 07-08-10, 07:40 PM
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Originally Posted by DataJunkie View Post
65-75 being my sweet spot.
+1, But today I actually found myself climbing faster than usual back home, strong headwinds, fog and it was pretty wet. It was in the mid 50s.
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Old 07-08-10, 07:43 PM
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Originally Posted by Daytrip View Post
Maybe I'm just getting stronger (finally), but I've had some really fast rides recently in this hot, humid weather. Maybe it's the lack of wind, but it just feels like there's less resistance on all fronts.

You'd think the opposite. You'd think your body would slow down in the heat and humidity. You'd think your tires would get soft and slow down on the soft road surface. You'd think that the humidity would make the air heavier and thus create more friction.

That's the trouble with thinking.

Anybody else notice this?
This. I don't care if it's 0ºF or 110ºF, lack of wind makes my ride better. Faster. Stronger. Like the Six Million Dollar Man.
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Old 07-08-10, 07:51 PM
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More humidity means less evaporation. Less evaporation means less cooling. More fat means more insulation.

More insulation plus less cooling means wanders rides in basement in front of fan in A/C.
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Old 07-08-10, 08:31 PM
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Originally Posted by carpediemracing View Post
By May or June I've been riding for many months, focusing on getting stronger, racing weekly if possible, more than once a week if I can. Therefore, I am way more fit. I've done, I dunno, maybe 20 races? A bunch of group rides where I make extreme efforts. I'm way more fit than, say, I was in December.

Being fit makes me ride faster. Heat and humidity, in excess amounts, slow me down.

So my average speeds are up on my training rides (JRA rides mainly, where I just ride as I feel like riding), substantially.

But relative to other riders, I think I ride better when it's cooler out.

If nothing happens to me, I'll be even faster this fall, when it's cooler and less humid.

cdr
cdr - Does this mean you'll be out of shape by the time you come down to FL in December? hehe.

I've got more energy with cooler temps, but this is just my perception, nothing measured. It probably has very little effect overall, especially on longer group rides.
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Old 07-08-10, 08:37 PM
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Originally Posted by pdedes View Post
smaller riders have better heat exchange properties than larger riders. (volume:surface area)
Great, yet another reason I'm too fat for this sport.
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Old 07-08-10, 08:44 PM
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Um, let's see. Two scenarios:

1. You're in San Diego, 73 degrees, 40% humidity.
2. You're in Houston, 102 degrees, 85% humidity.

Now, who do you think is going faster?
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Old 07-08-10, 09:06 PM
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I just love the heat. I think I am faster when my muscles are really warmed up. When I ride in cooler weather (60-70) especially
when there is a wind (15-20MPH) and I am sweating I just feel tense and slow. I find wind on a HOT day more refreshing than annoying.
Once I roller bladed 25 miles in 97 degrees with a 107 humidex and almost turned around to do it again, but I was out of water
so I decided not to. The radio folks were saying STAY INDOORS AND DON"T EXERT YOURSELF.
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Old 07-08-10, 09:31 PM
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Toasty summer evening rides with little wind = smoking hot on the VeloVolmobile
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Old 07-08-10, 10:05 PM
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Perceived exertion also decreases while you are going through the process of heat acclimatization. I made an effort earlier in the summer to go out and ride when it was above 90 and for two weeks I felt like I could climb everest. So if you haven't been riding a lot in the hot weather, you might be going through the process now.

Here's the link: https://www.sportsci.org/encyc/heataccl/heataccl.html
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