[kjkjadksj]

I went from sea level to 11k feet in the same day many times before. I would say the altitude effect is there but not as much as you might expect. A little quicker to be out of breath a little longer to recover it. Not sure what it is like at higher elevations or greater daily altitude delta.

[nonameiguess]

I guess fitness makes a difference from what these other comments are saying. My ex-wife and I lived in Long Beach (which is obviously sea level) when we were in ROTC and pretty regularly took day trips out to San Gogornio and walked to the summit in about five hours, which is ~11,500ft. Not once did that have any noticeable effect, but we were both pretty serious runners back in the day trying to become Army officers. On the other hand, she tried to summit Aconcagua during a spring break and couldn't make it due to altitude sickness. I've never been higher than Mt. Whitney, personally.

Even if you don't feel it, the altitude still makes a difference, though. I recall doing two-a-day hell weeks at Big Bear at the end of summer cross-country training in high school and there was a 5k up there at the end of that week. We all got worse times than typical at sea level, and somewhat amusingly, I recall a high school senior from Rim of the World High School (who lived up there) getting 2nd place overall the first year I ever competed in that race, beating way more seasoned competitors just because he was used to the altitude.

It works in reverse, too. There was an officer in my Armor Basic Officer Course from Colorado who gave himself rhabdo during the two-mile test the first week we in-processed, apparently because he was so used to altitude that he hadn't quite acclimated to Fort Knox atmosphere.

[jltsiren]

If anything, fitness makes you more susceptible to altitude sickness. It's not an inherent effect, but rather your habits driving you to do things you shouldn't. You are supposed to take things lazy and slow when acclimatizing to high altitude. But if you're fit, you may be used to moving too fast and pushing yourself too hard. You may not recover from exertion as quickly as you expect, and you may end up climbing higher every day than you should.

Altitude sickness typically starts after 12–24 hours. If you climb high and come back down in the same day, there is usually not enough time for the symptoms to start. And 11,500ft is not that high altitude. People routinely fly to Cuzco, La Paz, Lhasa, and Leh from sea level, and most of them suffer no serious ill effects.

[simplyluke]

It's pretty widely accepted in the climbing world that the primary effect of altitude in the short-term is a reduction in your cardiovascular fitness.

The better your heart is at getting oxygen into your muscles and organs, the better it can compensate for less oxygen.

Not a bulletproof solution to altitude sickness, but it's definitely one of a lot of variables that matters. It's also just true that some people are way more susceptible regardless, I've got friends who run competitive marathon times who get splitting headaches flying from sea level to denver.

[hermitcrab]

>I guess fitness makes a difference

Not really. Altitude sickness seems quite random in who it effects worst. I trekked to the top of Mera Peak (~21,000 ft) many years ago. 3 of the fittest people in our party got altitude sickness and didn't make it to the peak.

[prasadjoglekar]

Very much dependent on age, rest and general conditioning. I went from sea level to 14K at Pikes peak in 1 day and it was quite uncomfortable. I managed, but folks who lived in Denver with lower physical fitness levels than me, did better.

[linsomniac]

Agreed, we live at ~5K and went up to Pikes Peak; my wife and I had no problems (beyond minor headache), but my son's lips were turning blue and he was feeling pretty bad.

Other amusing things from that trip: we went up there the 3rd of July, and it snowed. We charged the car in Colorado Springs before we left, got up to the peak with 36% battery remaining. My wife worried we wouldn't be able to make it back. Got back to CS with ~70% battery left.

[FartinMowler]

Lol, on my trip up Pikes Peak I was blissfully unaware that altitude sickness could be a thing. So I can't recall if I felt any different. I do recall the carburetor on my motorcycle was acting a little strange, however.

[quickthrowman]

I went from ~500 ft above sea level (Palm Springs) up to 8,500 feet above sea level (San Jacinto Peak) in less than an hour via the aeria tram a couple months ago and it was very noticeable, my walking speed fell by a third and I was breathing a lot harder than I usually do.

[ahepp]

San Jacinto is 10,834 ft, for what it's worth.

[dlenski]

Same. I've climbed Mount Adams (12,280 feet) several times, including once with an overnight stay at 9,500 feet as well as other times when I did the whole ascent and descent in a single day.

It's a tiring climb and a tiring descent, but I never felt a hint of altitude-related discomfort.

I lived near sea level and didn't often go anywhere more than about 1,000 feet above sea level in daily activities.