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  1. #1
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    Oxygen content of humid air vs altitude.

    I live in Central NC and am training for a Fall trip to the Rockies. Since humidity is commonly 60% or higher and thus oxygen content is lower. I'm curious how this translates to riding at altitude, say 10k feet or
    Higher where oxygen is more limited. Anyone have any insight. Google isn't much help.

    At the end of the day I'm not too worried about it more so just curious. Have a feeling I'm gonna be struggling going from sea level to 10-12k feet overnight and my buddies are gonna leave me in the dust.

  2. #2
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    Nope. While humidity definitely affects the amount of O2, altitude (pressure) is far more significant. Although I ride in AK at sea level (O2 rich) I also ride in TX in the summer, which is simply torture with the humidity and heat, doesn't really do anything for altitude IME, raced a month later in AZ at 6K+.

    Best bet is to be aerobically efficient and in shape. This has worked for me (coming from sea level to Colorado above 12K). Give yourself a day or two to get used to it, maybe start off with some DHing at Trestle or something.
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  3. #3
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    Not sure about your actual question and how that is/works. Can say though, that coming from sea level to those altitudes, coming from a place who's yearly daytime low never goes below 25c/77F (that's a few days a year), normal temps are 30-31C/86-88F, and humidity is mostly also above 60%, it has made it easier for me than people from cooler, less humid climates or who spend more time in AC. I also have been relatively fit when I've been to those altitudes, which definitely helps immensely.

    By my rough calculations, going from sea level to roughly 10k feet, you loose about 30% of your oxygen intake due to the altitude and your corresponding lower max HR achievable to move the oxygen through your body.
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  4. #4
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    In rough numbers, going from really dry to really humid will lose you about 1% of you oxygen content. The more water in the air, the less room for oxygen.

    Altitude has a MUCH larger effect though. For every 1000 feet of elevation, you lose approximately 3% of oxygen content. So if you're going from sealevel to 10k feet, you lose about 30%. Huge difference. I lived in Colorado for a long time, and hiked 14,000+ ft mountains. Being fit helps, but if you're going there to race, you're probably already doing everything you can to be fit in the first place. There are two things that will help you more than anything else. First, get to Colorado as far ahead of time as you can. Just being at altitude gets your body to start figuring things out. Some workouts will help too, but if you're only there a few days in advance you probably want to keep exertion light or you'll just be tired for your race. Now if you were there 7 days early, then go out and wrack your lungs, but still only light the first day or two, and rest is key too or you won't recover from your workouts. Still remember to have a couple rest days before your race.

    The other huge thing is hydration. Higher elevation means dryer air, which strips your lungs of the water in your body constantly. I forget the exact math but the higher elevation means the rate of water loss increases the higher you go. Also altitude sickness has greater effects when you are dehydrated, so this is a compounding effect. Basically, I would say that the more water you can drink the better off you are, within reason. It means pre hydrating for your race is all that much more important, and you will want to drink more on your ride than you are used to.

    If you are at altitude and start vomiting from altitude sickness, unfortunately the only good solution is to keep drinking as much water as you can and get to lower altitude. This is your body's way of panicking and it is telling you that it can't maintain itself with this little oxygen. You should not have quite as much of an issue if you can at least get there a couple days in advance to let your body start to acclimate. Even world class athletes won't do well if they get to high altitude in immediately do a workout.

    In short, has much acclimation to altitude as reasonably possible, extra hydration for most of the trip, and extra rest to let your body adjust and recuperate. Do those and at least you're doing yourself the best favor you can. Altitude sickness honestly should not be an issue as long as you do the things above. I only threw that out there just so you know if you get sick what is actually going on. It's not a joke, and can really ruin your day, or your trip entirely if you let it go too far.

    Enjoy your trip! Biking in Colorado is amazingly fun and can be a trip of a lifetime. :-) don't stress it too much, just go and enjoy yourself. Just be as smart about it as you can.:-)

    Edit: thinking about it, I think it was at something like 14000 ft that your body loses one liter of water per hour just due to evaporation out of your lungs. Crazy huh?

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  5. #5
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    This can be a complex discussion, but in my experience, frequently going high from a home base of 500 feet, all you really need to know is what Jayem said "Give yourself a day or two to get used to it".

    I've read all the stuff about acclimation taking at least 5 days, but I don't buy that for fit cyclists. I know if I don't go too crazy the first two days, I can just do what I want starting on Day 3 without any ill effects.
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  6. #6
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    Actually it's 3 weeks to properly acclimate to those sorts of changes for most people and I can attest to that being accurate. Yes you can go and perform pretty good at those altitudes if you're fit, but spend 3 weeks there, making sure to not ride from day 18 and then get back on the bike on day 21.
    Will never forget my experience with this, got to that altititude after moving up gradually from 5k 2 weeks earlier, felt like the first time I was trying to ride a bike when I hit the hills and the same for the next 2 days, then took 3 days off to rest before my "race" and then on race day felt so much stronger I could not believe it, but sadly had slotted myself towards the back going from earlier rides in the week, not wanting to hold anyone up

    Will say that this last time up I was no where near as fit, but had been riding constantly for the 9 years, so body was much more accustomed to knowing how to efficiently turn the cranks over, and despite not being as fit, still managed pretty good.

    Quote Originally Posted by kosmo View Post
    This can be a complex discussion, but in my experience, frequently going high from a home base of 500 feet, all you really need to know is what Jayem said "Give yourself a day or two to get used to it".

    I've read all the stuff about acclimation taking at least 5 days, but I don't buy that for fit cyclists. I know if I don't go too crazy the first two days, I can just do what I want starting on Day 3 without any ill effects.
    One day your life will flash before your eyes, will it be worth watching??

  7. #7
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    Quote Originally Posted by LyNx View Post
    Actually it's 3 weeks to properly acclimate to those sorts of changes for most people and I can attest to that being accurate.
    Right, actually, I guess I'm just lucky (as is my wife) because we find that by Day 3 we're raring to go.

    Racing 100s at high elevation immediately is a near-death feeling for me, but if I do a 50 on the same course, I don't even think about elevation.

    Humidity is another thing altogether. I'm not sure about the exact science, but personally, I truly despise humid weather!
    Whining is not a strategy.

  8. #8
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    Was that a typo and it should have been 5,000ft? If you're only going from 5k feet up to 9-10k, that's a different story, but if you're going from sea level to 9-10k, who nother ball game.

    When I arrived at 5k feet from sea level, I was actually good, or so I thought, then went to 7400ft-8400 ft and did the Laramie Enduro and took 9 hours and thought I'd nearly die a couple times, had no intention of doing anything but volunteering at Leadville after just 11km and 7500ft of climbing at only a max of 8400ft. By the time I got to PBville 9 days after later spending the time moving about CO riding and up in elevation, I was feeling much better, but still walking up the town roads killed. Took 2 days off the bike to let the body acclimatize, but even after 2 weeks at altitude, I had the feeling of noodle legs and no oxygen on any decent climb, but then on race morning, 3 weeks later after taking 3 days rest, I was absolutely fine, could not believe how different I and my muscles felt.

    As to humidity, it seems to help me now years later when I go to altitude because I'm also accustomed to serious heat along with the humidity. I've had NUE Series race fit, riders come down here and suffer way worse than when I went to altitude because of the heat and humidity.

    Quote Originally Posted by kosmo View Post
    but in my experience, frequently going high from a home base of 500 feet
    Right, actually, I guess I'm just lucky (as is my wife) because we find that by Day 3 we're raring to go.
    Racing 100s at high elevation immediately is a near-death feeling for me, but if I do a 50 on the same course, I don't even think about elevation.Humidity is another thing altogether. I'm not sure about the exact science, but personally, I truly despise humid weather!
    One day your life will flash before your eyes, will it be worth watching??

  9. #9
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    I agree w LyNx. It's not a 5 day process to completely acclimate. They say it takes 3 to 4 weeks when you move there. I guess the takeaway point though is that the more time you have the better. I would say you're silly if you don't have at least one day to acclimate. At least two days would be smart if you want to do well. Three or more days is ideal.

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  10. #10
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    Quote Originally Posted by LyNx View Post
    Was that a typo and it should have been 5,000ft? If you're only going from 5k feet up to 9-10k, that's a different story, but if you're going from sea level to 9-10k, who nother ball game.
    500 feet home base to riding around 8,000, definitely different than 10,000!

    When I first did the Butte 100, I had one day of acclimation for reasons beyond my control. The highest part of the race was between 75 and 95 miles and it damn near killed me.

    Then I went back and did the 50 with two days acclimation. The highest part of the race came between 30 and 45 miles, and I never gave it a moment's thought.

    Altitude acclimation is a very personal thing. I've got one friend that is a freaking animal, backed up by numerous titles, but altitude KILLS him. Another roadie friend is an actual masters world champion, and he just isn't phased in the least by elevation. Side story is that by profession he was a volcanologist (sp?) so spent tons of time in the field at crazy elevations. He says he always wondered why everybody else had so much trouble, and he never noticed anything unless they got over 15,000 feet. I guess my wife and I are somewhere is the middle, at least at modestly high elevations.
    Whining is not a strategy.

  11. #11
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    Two weeks in the mountains can change your blood for months | Science | AAAS

    Your body can adapt overnight according to the latest science but takes months to build more red blood cells. As a dabbler in mountaineering for many years I can say without question alcohol and caffeine are not your friend here. Don't have any at least 30 days prior. I start to feel elevation at right around 6500ft but doesn't hold me back untill around 16000ft at which point it takes me a solid month to perform at 100%.

    Edit*- aspirin or something to thin your blood can really help.
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  12. #12
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    Quote Originally Posted by WHALENARD View Post
    Two weeks in the mountains can change your blood for months | Science | AAAS

    Your body can adapt overnight according to the latest science but takes months to build more red blood cells. As a dabbler in mountaineering for many years I can say without question alcohol and caffeine are not your friend here. Don't have any at least 30 days prior. I start to feel elevation at right around 6500ft but doesn't hold me back untill around 16000ft at which point it takes me a solid month to perform at 100%.

    Edit*- aspirin or something to thin your blood can really help.
    Interesting article. It makes sense that your body adapts rather vigorously to environmental changes; many animals do the same thing.

    However, the article doesn't really refute the idea that it takes a while to FULLY adapt. Yes, your body immediately starts producing more red blood cells when you arrive at altitude. But you don't max out for a couple of weeks. The RBC count vs time curve is steepest in the first couple of days, but doesn't level off for 3-4 weeks.

    I just moved from 5,000ft to 7,200ft. The difference is noticeable and definitely impacts my performance. However, my body is adapting to the new "normal", and will make 5,000ft feel great in comparison. I'm regularly riding at 9,000-10,000ft here.
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  13. #13
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    Curious if you've ever spent some decent time, like 3 weeks at altitude to see what or if your performance improves? My guess would be no and that if you did, you would realise that while you adapt to the altitude fast for the few days/week you're there, if you stayed at that height for 3 weeks you would see a definite performance improvement over the first few days when you first arrived.

    Oh and yes, 8k isn't 10k I was moving all about up to a max of 8400ft in the time leading up to going to Leadvillle and thought that extra 1800ft wouldn't be a big deal, but boy was a I wrong, it was like now starting out riding a bike for the first time nearly, or that's how it felt for the performance hit I took.

    Quote Originally Posted by kosmo View Post
    500 feet home base to riding around 8,000, definitely different than 10,000!

    When I first did the Butte 100, I had one day of acclimation for reasons beyond my control. The highest part of the race was between 75 and 95 miles and it damn near killed me.

    Then I went back and did the 50 with two days acclimation. The highest part of the race came between 30 and 45 miles, and I never gave it a moment's thought.

    Altitude acclimation is a very personal thing. I've got one friend that is a freaking animal, backed up by numerous titles, but altitude KILLS him. Another roadie friend is an actual masters world champion, and he just isn't phased in the least by elevation. Side story is that by profession he was a volcanologist (sp?) so spent tons of time in the field at crazy elevations. He says he always wondered why everybody else had so much trouble, and he never noticed anything unless they got over 15,000 feet. I guess my wife and I are somewhere is the middle, at least at modestly high elevations.
    One day your life will flash before your eyes, will it be worth watching??

  14. #14
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    The difference in pressure is logrithmic, so the difference from 0-5K is greater than from 5-10, although still decreasing.

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