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Saturday, July 07, 2007

Altitude training - the basics

So I really struggle to come up with a decent post for today, felt like doing something on cycling again, now that Jorg Jaksche has admitted to doping and suggested it is pervasive in the peloton. For some classic quotes, have a look at this article. The most telling this is the reaction of the other cyclists - Jaksche has been crucified by his former collegues and competitors, and that alone is an indication of the culture in the sport - it's as if they take the Hippocratic Oath equivalent of never-tell. Just ask Floyd Landis

But, with the Tour de France coming up over the next three weeks, I figured there would be plenty of time to talk cycling, so keep an eye out for some 'behind the scenes physiology of the Tour de France in the upcoming three weeks.

But for today, I thought I would go back to something that came up about 2 weeks ago, during a post on EPO use. Lei asked about altitude training, so I figured I'd do a short post on the benefits, if any, of training at altitude. And then Jonathan could follow up with some more information.

As I'm sure many of you know, most elite athletes now do some sort of altitude training before major competitions. I'm not 100% sure where the concept began and how it was realised that a period of altitude training might improve performance. I suspect that it was a result of the opposite being true - when athletes from sea level went UP to altitude, their performance suffered badly - I'm sure many of you can relate! The most vivid illustration of this was the 1968 Olympics (the year of Bob Beamon's mammoth long jump record, thanks in part to the thin air in Mexico City), when Ron Clarke of Australia collapsed and nearly died from altitude sickness sustained during the grueling 10,000 m race final. It was reported that he suffered permanent heart damage from this event.

In addition to this, there was the obvious experience of mountain climbers who would feel vast improvements in their condition having spent a few days acclimatizing to high altitude, and then returning to slightly lower altitude. So it's not all that surprising the people felt there was a possibility that training at altitude would improve sea level performance. And that's what this post is about - we investigate whether this is in fact the case.

First question - what is the basis for altitude training? Should it even work?

OK, so this might seem like a silly question, but in fact, it's quite key to all of physiology. The theory behind exercise, until relatively recently, is that you have to slow down because your heart is unable to pump enough blood (and hence oxygen) to the muscles. The result is that the muscles become what science calls "anaerobic" (without oxygen), and they accumulate lactate, eventually forcing the athlete to slow down. The root cause of all this, of course, is a lack of oxygen supply to the muscle - demand exceeds supply, and you get "poisoned" by lactate.

However, there are a couple of pretty major flaws with this theory. I won't go into them in detail here, but let's just say that it's unlikely that the heart is ever unable to supply enough blood. And if the muscles ever ran out of oxygen, they would go into a state of rigor, where they'd stiffen up and not relax properly. And this doesn't happen, so there is something wrong with this picture. However, it is the basis for why altitude training would work, and so we'll stick with it for now.

So the theory is that at altitude, your body adapts to the lower oxygen pressure in the air, and these adaptations ensure more oxygen delivery to the muscles. The main adaptation is that the body naturally produces more EPO, which means more red blood cells, as we said in our previous post on EPO use.

And more red blood cells means more oxygen in a given volume of blood, which means longer for the muscles to run out and delayed lactate accumulation, and so on. There are some other theories and adaptations, but we'll keep it short for today!

So does altitude training work?

Knowing the basics of the physiology, the next question is does it work? This is a slightly controversial one because the science and the anecdotes don't agree. The athletes swear by altitude training, the science has often failed to find an effect when studies are done in a controlled way. And that's what we need to consider.

The burden of scientific stringency

The first thing to remember about scientific studies is that they impose a stringency on the volunteers that may or may not make it easier to find a difference. In otherwords, a proper scientific study has to control all sorts of variables that would possibly influence the outcome, and in the case of altitude training, it's quite possible that controlling these variables will prevent a positive result from being found. For example, a normal altitude training excursion is remote, allowing the athlete to escape his or her normal routine, train perhaps three times a day, away from the distractions of normal training. And this change in approach has often been cited by scientists as the reason that altitude training works. A scientist by the name of John Hawley once wrote an article called "Altitude or Attitude?", and he claimed it was the attitude change of an athlete going to a dedicated training camp that made the difference, and it would not have mattered if it was 3000 m or sea-level.

Another issue is statistics. In science, a difference in performance must be shown to be statistically significant, which means that it is not due to chance. And science sets all kinds of limits or confidence ranges on a result, and this influences its interpretation. So for example, a 10 second improvement in a 5 km time-trial might be found to be insignificant in a scientific study. However, there are athletes all around the world who are training for 3 hours a day to find those 10 seconds, so there is sometimes a difference between what is a "Statisticially significant difference" and a "Real difference". A sports scientist and statistician in New Zealand, Will Hopkins, has developed a new method of stats where he looks at something called "Meaningful difference" and this might be the key to understanding and interpreting altitude physiology.

So despite the inability of science to find an effect, my feeling is that there is still something to altitude training, so we need to dig a little deeper. There is a physiological basis for why altitude training would NOT WORK, and that's important to consider. Remember that the theory is that at high running or cycling intensities, the demand for oxygen supply becomes great enough that the body cannot meet that demand and you slow down. This means that the high intensity running sessions are limited by oxygen. And when an athlete is as altitude, this limit is even greater. So what happens, then, is that an athlete at altitude gets benefits from the increase in EPO and red blood cell mass, but they are actually disadvantaged when it comes to doing the higher intensity training sessions. They simply cannot train hard enough at altitude, and that may offset any benefits they could have derived the other way.

This is the reason for the development of the "live high, train low" theory. What athletes began to do was to find locations where they could live at a reasonably high altitude, sleep there and do all their easy running so that they got the benefit of increased red blood cell levels from EPO. But they trained at low altitude, coming down from their 'mountain tops' to do their harder training sessions. Obviously, this is a massive logistical issue - how many locations are there in the world that allow you to drop down from an altitude of 2000m or higher to an altitude of 1000 m or lower to train? But then technology stepped in, and altitude tents and hypoxic houses were developed. This meant that an athlete could sleep at sea level, but in an altitude tent that simulated an altitute of about 2500 m, but then wake up in the morning and head out for a training run at sea-level! And everyone was using them - Paula Radcliffe, Lance Armstrong, the Australian Institute of Sport, Jan Ullrich (apparently). The World Anti-Doping Agency even considered banning them at one stage for the 'unfair' advantage they might give!

But the evidence suggests that this live-high and train-low theory does work,though the effects are relatively small. There is also an interesting phenemenon of "responders" and "non-responders", with some people showing improvements of about a minute over a 5km time-trial after a 4-week training period, while others show no improvement, or even get slower. So the jury is still out, scientifically at least. But the fact that so many athletes swear by it is a sign that there is something there, even if it is just a placebo effect.

The paradox of performance - which events should benefit most and which do?

One last thing to consider and perhaps this is the most interesting thing about altitude training - there is a paradox about which events are improved most, compared to which should be, according to the theories for why altitude training should work. Remember, we've said that the theory behind altitude training is that it improves the body's ability to deliver oxygen to the muscles. So in theory, this means that it should have the greatest effect on events where oxygen supply is likely to be limiting. Which events are these? Well, in a marathon, the evidence suggests that athletes are running at about 70 to 80% of the VO2 max, which means they are not actually at that limit. Yet altitude training is supposed to work for the marathon!!! Even in our Comrades Ultramarathon, the Russians who regularly arrive and clean up the medals credit altitude training as a reason for their success - Comrades is done at 50% of maximum oxygen use, so clearly, if altitude training is working, it's working well below the apparent limit. And the current understanding of physiology does not allow us to explain this observation. The same goes for what happens when races are run at altitude - the one where performance suffers the most is the marathon, even though it's not limited by oxygen in the first place! The 10000 m event, which is done at about 90% to 100% of VO2max, and the 5000 m, are affected much less by altitude or altitude training, and so clearly, we're missing something as scientists here!

Take home message is that when someone tells you they know the answers about altitude training and why it works, you can quite rightly challenge them, because a lot doesn't quite add up. But altitude training works, there's little doubt about that, but apparently only in some people and under some conditions. One of the great things (or not so great...) about science is that there's always a "but"....!!

Ross and Jonathan


Philippe said...

I don't know if anyone still reads the comments on these old posts......

I'm not an exercise physiologist, so maybe you can clear something up for me. Both your post on EPO and this post seem to work under the assumption that better oxygen delivery (higher hematocrit levels, etc.) should be useful really only if the exercise is anaerobic. Hence the paradox of why endurance events are most affected when changing altitudes (and not sprints), or the unexplained reason why EPO should help cyclists in the 3 week Tour.

It is my understanding that athletes produce lactate even when exercising aerobically. Of course, greater exertion (pace/HR) produces lactate at a greater rate. Up to a certain point, this is balanced by the body's ability to clear lactate . Increasing, fixed, exertion levels therefore result in increasing steady state lactate levels until a point when the body is overloaded and lactate then accumulates faster than it is cleared.

The production of lactic acid is the result of an anaerobic process (pyruvate -> lactate in order to regenerate NAD+ and allow glycolysis to continue). Therefore, it would appear that even at exercise levels that are not anaerobic on an overall body level, the muscles are working partially anaerobically (to a degree determined by exertion level).

Could the EPO or altitude effect therefore have to do with allowing the muscles being used to do a larger percentage of their work aerobically? This could avoid the wasteful conversion of glucose to lactate in the muscles and lactate back to glucose in the liver. It would probably increase the % of energy that comes from B-oxidation and therefore preserve glycogen for later in the event.

I think the key distinction could be: not whether the overall process in anaerobic, but whether ANY small part of it is. That part could benefit from greater oxygen delivery.

Am I missing or misinterpreting something? Thoughts?

Ross Tucker and Jonathan Dugas said...

Hi Philippe

You're onto something, yes! Your argument is very well constructed and developed, and very impressive...but (there's always a but!)

Your starting point is that the accumulation of lactate is the thing that must be avoided - so therefore, your 'end-point' or limiting variable is the formation of lactate at a rate greater than can be dealt with by the body.

So while your physiology is sound and the explanation is true in principle, I would question that the formation of lactate is either 'wasteful' or 'harmful'. The latest theory, developed by a guy called George Brooks, is that lactate is in fact the body's most crucial form of fuel during exercise, because it gets energy around the body very effectively - in otherwords, it is converted to lactate in muscle, then released into the blood, take up by other muscle and used as energy.

So rather than being the "bad guy", it's actually crucial for optimal muscle function! There are studies (admittedly, in vivo ones) that have found that the addition of lactate to muscle INCREASES the ability of the muscle to contract, rather than disturbing it and impairing muscle function.

So all in all, the jury is out on this one. We've been promising our regular readers a series on lactate for some time now, and we definitely plan to do it in the new year, if you can be patient! Otherwise, look up George Brooks for some really interesting and novel theories.

But returning to your question, I do agree that the effect of EPO and altitude training is probably exerted by changing the level of SOME SIGNAL. But here, you have to realise what a radical difference this is from the existing theory. The existing theory is that lactate (or some other metabolite) acts directly on the muscle, causing it's function to be impaired.

What you have suggested, and what I agree on, is that there is a SIGNAL which plays a regulatory role - note the difference here: One theory says that exercise is limited, the other that it is REGULATED. And so yes, I agree that what EPO probably does is SIGNAL to the brain that the athlete can exercise a little bit harder before the levels of that REGULATORY variable increase (or decrease) so much that exercise will be impaired. There is no physiology text-book that will tell you this - so what you have suggested is revolutionary and contradicts the prevailing theories.

But this is a theory that we are trying to develop - I did my PhD on fatigue and the regulation of exercise, so it's right up my alley. The easiest example to illustrate it is body temperature. The current theory, as explained by the CLASSIC science, is that when you exercise in the heat, you slow down because you get too hot. This is wrong. The real reason you slow down is so that you don't get too hot! In otherwords, the brain is monitoring the body - body temperature in this case (it could also be pH, glycogen availability, probably pO2), and then making a decision about whether you should slow down, keep going, or speed up based on this variable. When it is very hot, the brain forces you to slow down because it calculates that if you do not, then your body temperature will rise to reach possibly limiting levels. But it doesn't happen, and that's the beauty of an "anticipatory system".

Applying this to EPO, I suspect that EPO alters the pO2 enough that the brain, which is monitoring pO2, allows the athlete to push a little harder before the pO2 becomes important.

So yes, I agree with your theory, but just don't think that lactate is at play here, it's something else.

There are probably many questions about this, and we will tackle all this in a series some time in 2008. But it's a mammoth topic, so it will take time to develop the arguments. So be patient with the 'holes'!

Thanks again for your post, very thoughtful and well argued!


Philippe said...

First off, let me say how great it is that you guys are so interactive with your readers! Much appreciated and very informative response. I will be patient and await your upcoming posts on this topic. In the meantime....

On lactate - I don't think lactate is the enemy (Under Armour ads have already taught me that 'cotton is the enemy' anyways :). It would make no sense for the body to waste energy stored in the form of lactate, and so the efficient transport and use of lactate as explained by George Brooks makes sense. Whether the breakdown of a glucose molecule that passes through lactose is more or less efficient in terms of ATP produced than direct oxidation of pyruvate is another question.

That question aside, lactate production is a result of glycogen/glucose use as a fuel. Even if we assume no ill effects of lactate on pain, muscle contraction, or perceived exhaustion, can we assume that the greater the lactate levels observed the more glycogen is being used? Because glycogen is in limited supply, the faster you use it the sooner you will 'bonk', 'hit the wall', etc. Glycogen depletion only occurs with longer events (consistent with those that benefit from altitude training). Therefore, could the altitude effect be to shift fuel source from glycogen to fats? Lactate in this sense is a marker of fuel source, not a problem in and of itself.

The key to my hypothesis hinges on the assumption that greater O2 delivery to working muscles allows those cells to use more fats and less glycogen as fuels. I base this assumption on the fact that the glucose -> pyruvate -> lactate conversion is anaerobic and can/does occur when O2 is limiting whereas beta oxidation cannot. Therefore if cells need energy, but don't have O2, glycogen/glucose must be the source (right?).

So if temporary/local O2 deprivation causes lactic acid fermentation, regardless of whether that lactate is used as fuel later on(which it is), that local hypoxia has committed the muscle to burning more glycogen to meet its energy needs.

Of course, logic often fails when applied to biology so let me know if there is evidence against any of my steps here.

On signals and anticipation - I look forward to hearing about your more of your research on this. The most interesting question to me is whether the brain is generally spot on, or too conservative in terms of performance. If I can trick my brain into allowing me to run faster in the heat, I might win the race, but at what point have I put myself in danger? Are the brains of elite athletes better at pushing the envelope than recreational athletes... either through training or b/c this is one of the things that enabled them to become elite to begin with.

GZ said...

Is it fair to assume that training at altitude would be effective for performing at altitude?

Specifically, there are several high altitude endurance events (Pikes Peak, Jungfrau, etc). It would seem to me that preparation (training) for these events ought to include significant time at altitude (to be the most comprehensive training possible).

In other words, train high to race high?



Ross Tucker and Jonathan Dugas said...


Absolutely - if you know you're going to be competing at altitude, it's imperative that you spend some time training there before. The trouble is that no amount of training is ever likely to get you to the level of a local, altitude native, particularly at the high altitudes. So we know pretty well that the body takes between a week and three weeks to adapt, depending on the atitude, after which performance begins to return to "normal".

I say "normal" because it's impossible that performance at 2000m above sea level will ever return to performance at sea level, but there's most definitely an improvement by about a week. The other option, if you're competing ina short, single day event, is to fly in, get the event done, as quickly as possible. Many rugby or soccer teams do this - fly in perhaps 3 hours before, play, and then leave when done. That's the other option.

But I'd certainly be spending some time at altitude, because the physiological responses are essential to getting performance back up to normal levels.


stokes said...

As an athlete i am constantly searching for ideas and theories behind why training methods work.It has become my understanding that altitude training is desined to increase an athlete oxygen carrying campasity,this is done by the lungs surface area increasing my reducing the oxygen levels within the air.This forces the body to adjust it's air intake ,resulting in the alvious (air sacs in the lung from which oxygen diffuse into the blood stream)becoming mor abudent,in turn increasing their overall oxygen carryiing capacity.The greater the oxygen intake , the slower lactate is formed.
Great topic none the less

sdaghir@gmail.com said...

I love the work here and have been an avid reader for a few months now.
I am really hoping you get notices when people post on your older articles, your insight and opinions would be tantamount to celebrity status for me.

The presentation of "science" that you guys use here is unique in a way that appeals to polar realms of human curiosity. Its great that there are people posting comments here that would probably like it if science was primarily something that invloved "finding answers through experience" as opposed to those who like the idea of "forging law through analysis".

I know this is simplifying us as humans, and I by no means think science can ever be fully debated and defined in blacks and whites. I just wanted to explain why I think your mindset appeals to me and is an asset in helping me ask some questions that I think yo will like to explore as well.

I always got in trouble growing up for asking too many questions in class and got angry because no one would try to answer them. Instead I went out and found my own answers which either made perfect sense to my little childhood world or didn't. As a grown up (I pretend to be sometimes) I get the impression from my peers that science has become more of a way to justify the blind faith that is needed just to begin reading a journal article which presents soemthing you feel falls into the category of radical or contrarian theory.

I share a lot of thoughts, ideas, and questions with an excellent group of people through a blogger page like yours, and I love the contributions they make back into the discussions and you obviously have a similar apprecaiaton for that.

The only real problem I run into that isn't conducive to an open minded environment for concept growth seems to be an
expectation that everything has a yes or no answer with really fancy signitures from important scientists.

In the end I have come to think that for those that could care less about the methods of science are just lazy, and don't feel that the hunt for an answer or the arguments sure to ensue as a product are worth the time.

Wow, didn't mean to be long winded but I wanted to know what you thought about that, and if there are certain circles of resources you frequent when seeking hard numbers, or if there were particular places you relied on to find more than a "one word answer" and sometimes maybe just ended up producing more questions?

I am trying find sources that I can bring into our fold so these guys can go run them down and get more out of it than a sigh of relief that some heretic wasn't poisoning their minds. The current hunt involves looking at the efficacy and effects that could come from variables involved in adjusting elevation as a part of training. Beyond this I wanted to draw some similarities and find some studies that involved restricting the quantity of oxygen involved per breath as well as volume of air. I train with a gasmask on frequently and want to see how well that tool can be used to simulate most obvious variables that change during elevation changes. One final step beyond that would be to see if there would be a method of adjusting the factors of stress involved in elevation through rapid and random increments inside single sesions of training and watching how this would affect an athlete. I have my theories, but I would like to make sure you wouldn't mind helping me here and that I am not bothering or corrupting your audience with something does not represent your personal realms of interest and curiosity.

If you give me your approval then I will come back around with progressions into the realm of blood analysis which can keep me asking questions for eternity but with emphasis in
how to use not just elevation
oxygen deprivation as potential catalysts of an ogranisms ability to rapidly adapt, but also the effects are possible to elicit from submerged exposures to many of the same variables that are changing in elevation.

Ok, I will shutup now, Thank you so much for your time and all the great knowledge so far that I have been trying to share with any one that will listen.

I appreciate your value with full disclosure and if anyone wants to contact me they can feel free to email sdaghir@gmail.com