Mt. Whitney Portal Store & Hostel Forums General Mt. Whitney Portal Store Message Board When do you really notice the altitude?

I've gotten out of my car in the mountains, started walking up a steep trail, and said something like, "Man, the air is thin up here!"

But...

Recently I noticed that if I get out of the car and start walking up a steep trail at the beach, it feels almost exactly the same!

Here's my impression: The altitude really doesn't seem to do much to me until I get to around 12,000 feet. At that point, it has a strong impact - it takes away about half my capacity to move uphill. I find it fascinating.

Does anybody else have a sudden threshold? I'm curious if everybody has the same experience at around 12,000, or if some feel it lower and some higher.

Incidentally, I'm not talking about life-threatening altitude sickness, I'm just curious about the average hiker plugging along a mountain trail.

z

Yes, I too have hiked Whitney a few times and hiked much of the sierras. Almost always i feel the effects at 12-13,000 feet. I have to spend almost a week in the backcountry before I feel good at those levels or higher. Otherwise, I grin and bear it.

I have a few theories about Whitney and the 12,000 mark. This has to do with one has been on the trail for a at least 4-5 hours, low on hydration and not hungry, and the elevation gain per mile is one of the greatest on the whole trail just before getting to trailcamp (getting to trail camp pooped). People tend also to take too long of breaks at trailcamp. There is usually more sun and the heat of the day is on us.

All these factors are things we can modify. But overall, we just need to grin and bear it or turn back down.

Yes, Trail Camp is usually where the altitude starts to affect most people who trained and acclimated for a day hike. Not only is it at 12,000 feet, but the slope of the trail increases slightly when you go through the 97 switchbacks.

My magic number is closer to the 13500 mark if I feel it at all. When I had the stomach issues the last time, I wonder if it wasn't dehydration that was getting me and not AMS. I certainly didn't have the headache or any other of the classic symptoms. When I summited a couple of days ago, I was consuming alot more water, but I was slowing down ALOT after trail crest and it was there where I noticed my heart pounding alot harder too.

I have to agree with Fred, 12 to 13K I start to feel sluggish. Right around the cables usually.

I spent nights at 8k, 10k, and 12k before summitting and I didn't notice any significant difference between breathing at the summit and sea level. If there's a similar altitude when people feel the effects, that may be partly because they have had similar acclimitization preparation, partly because of similar hiking styles (hydration, amount of exertion, food intake, etc.) and partly because of their intrinsic physiology.

It seems to vary for me. The Drastic slowdown at altitude has hit me as low as 12,000' and as high as 14,000. I guess it depends on the day. I'll add that I rarely get a good chance to become well aclimated since I usually spend the night at Lone Pine before a trip in the area. When possible I sleep in the back of my pickup at a trailhead the night before a hike. Honestly I don't think this has helped me all that much.

Rafael...

I think altitude sickness is an individual thing. My wife's brother in law drove to a spot above 10,000 ft. in the Rockies and became very ill when he stepped out of the car. Perhaps he would do better if he took more time to get to that elevation, but he will never try again.

I definitely agree that it is an individual thing, and that training may not necessarily translate to tolerance of altitude.

I've done three 10K plus training hikes this summer preparing for my backpack trip this weekend, plus one overnite backpack trip to 11-12K, and I felt fantastic the whole time. Absolutely no symptoms at least to that elevation.

I have a friend of mine who is also in phenomenal shape physically, but who gets very ill even when she goes to about 6K ft (Lake Tahoe).

Slow acclimation is always best, listening to your body runs a close second (which goes toward pace), maintaining proper hydration and nutrition coming in next.

-Laura

I would say around 12k as well. Once I hit the switchbacks I have to slow down the pace or get burned out.

problem is not really the oxygen (it is 21% at all altitudes), the problem is pressure and how your body adapts (acclimatizes). Different for individuals.

Note that the official medical definition for altitude is >8,000 ft. Coincidentally (on purpose), airplanes pressurize cabins to,...guess what...8,000 ft.

Try a hike at 8,000, 10,000, 12,000 whatever. Come back and do it again after being in the high country a week or two. The difference in your own personal threshold (which is different from the next person) will be markedly different. This "front end" difference diminishes and therefter, people seem to be more similar. This excludes certain extreme-capable people who have an edge on any day, any altitude, any length stay.

Hey, here's something I found:

The standard pressure at sea level is 760mm Hg. Since oxygen comprises about 21 percent of the air, we would expect the dry air oxygen partial pressure in the lungs to be 159.6mm Hg (760 times 21 percent), but through physiologic processes, the partial pressure of oxygen in the arterial blood is normally about 100mm Hg.

Air inhaled into the lungs enters small air sacs (alveolus) where the exchange of oxygen and carbon dioxide occurs. When the partial pressure of the oxygen is higher than it is in the blood, oxygen molecules are picked up by the hemoglobin molecules. This hemoglobin saturation is approximately 97 percent at sea level.

The atmospheric pressure decrease at 10,000-foot altitude causes 523mm Hg ambient air pressure resulting in 87 percent hemoglobin saturation and 61mm Hg arterial oxygen.

At 15,000 feet (429mm Hg) the hemoglobin saturation is 80 percent (we need 87-97 percent for normal functioning), and arterial oxygen is 44mm Hg (the body requires 60-100mm Hg.).

For the full article, here's the link:

http://www.mountainflying.com/oxygen.htm

It looks like we're functioning with a little less oxygen than we need any time we're above 10000 (which would mean 8,000 mentioned above is a comfortable level for most of the general population). Of course, the body has adaptations for this, which begin immediately, but it would make sense that for day hikes the threshold would be more obvious (within 2000-3000 feet) and for those who spend more time at altitude the threshold would be less obvious or disappear until they get to extreme altitudes (say, above 17,000).

Still, it's odd that it can hit some folks suddenly, out of the blue, especially when they've been to high altitude before with no ill effects.

For me, I train on Mt. San Gorgonio - which goes up to 11,502. No effect. Above 12000 in the Sierras - I move slower and breath a whole lot more.

z

okay, getting technical here. By shifting the oxyhemoglobin dissociation curve to the left, you can improve the oxygen saturation to a level that is better than you would predict based on altitude/pressure alone. So the 87 % saturation you mentioned at 10,000 ft comes up (but not all the way to normal, maybe say to 90%)

In plain English, by hyperventilating both acutely and chronically at altitude, you shift the ph and other parameters in you blood which therefore alters how your hemoglobin (red cells) picks up and releases oxygen. This is a self-preserving mechanism. Some animals do this poorly (cattle), some superbly (bar-headed goose), some average(lowly humans)

It has been proven that man cannot PERMANENTLY adapt to live above 17-18,000 feet. For weeks or even months at these altitudes, but not permanently.

So you're saying I can probably beat a cow to the peak?

But seriously, thanks for the technical insight. I was having trouble reconciling the 87% with the fact that most people who are not at all acclimated (day hikers, for example) do not suddenly grind to a halt above 10,000.

Do you know the mechanism responsible for longterm adaptation? I've heard that hemoglobin is either increased or its formulation changes over a period of time to increase its ability, but I don't understand the process.

Would you be willing to give a simplification of that process too?
z

long term adaptation is "somewhat understood".

obviously hyperventilation is mandatory on an acute and chronic basis and is obvious for obtaining more oxygen and shifting the curve - mentioned above.

increased red cell mass (polycythemia)occurs with increasing altitude. Counterintuitively, it is controversial that this helps, despite "blood doping" in sports. But for sure, too much of a good thing can be detrimental. You can get too much red cell mass and thereby thicken your blood. Harder to pump, plus sludging in the tiny capillaries, particularly bad in the lung. Monges Disease with heart failure is caused by too thick blood in people exposed for very long time, say miners in the Andes. Also, it happens in cattle taken to high pastures(only 6000ft) in American West. In cattle, this is called Brisket Disease rather than Monges. It has been partially bred out now.

Lastly, changes occur at cellular level. Things like the mitochondria migrate close to the cell walls, and levels of 2,3 DPG rise and affect oxygen release. Very poorly understood.

For more see Bible:
High Altitude Medicine
Herb Hultgren
(Stanford Univ)

he took cath equip to the Andes many years ago and proved that HAPE ( High Altitude Pulmonary Edema) was not a heart disease but a lung problem. Many people quote Charlie Houston, but Hultgren's 1997 book is the gold standard.

Harvey

For me it is consistently 10k for signs of headache, nausea, etc. Doesn't matter what shape I'm in.

In terms of stamina / aerobic ability, I notice some effects even as low as 6k and the effect is greater as I go higher. Conditioning definitely helps this.

Three days of acclimitization at 8500 feet, a rigorous prep hike up Cloud's Rest and Half Dome, and learning how to do the special breathing thing from Kurt Wedberg almost made 14,500 at the top of the Class 3 seem like sea level. That, and choking down dinner for three whole days beforehand without benefit of the grape (at my age, a necessary if uncivilized part of the preparation). Otherwise I couldn't beat a cow to the top.

My only experience with high altitude hiking was Mount Haleakala in Maui. On that occasion, we drove from sea level to 10,000 feet and hiked about two hours down in the crater and back up.

I didn't notice anything walking downhill, but on the way up I was extremely fatigued and sluggish after just a few steps and it was a struggle to get out of there before dark.

So I definitely felt it around 9000 to 10,000 feet but that was after going from 0 feet to 10,000 feet in an hour or so...I hope that was a big part of the problem and I won't have a major problem with high altitude hiking (that would be a bummer).

Besides that experience, I've only hiked at around 8,000 feet and had absolutely no problems with that, but that is probably natural.

8,000 feet is the pressure standard that most jet airliners are designed to. Why? Because most people can handle the first 8,000 feet without a problem. If you normalize your elevations to 8,000 feet (by subtracting 8,000 from them) you get a more realistic metric for altitude effects. 9,000 feet is really only 1,000 feet above that threshold while 14,000 feet is 6,000 feet above that threshold.

Fred, so true about the airline pressure. However, I hear SO many people talk about getting ill after flying, which they usually blame on the "poor air" of the airplane, I have to consider that the actual problem is mild altitude illness. Never seen any research on it, though.