W/m^2, Altitude and the Hour Record. Part II

The Physics recap

In an earlier blog post I examined the influence of altitude on the physics of cycling’s world hour record, and showed how the reduction in air density as altitude increases means one can travel faster for the same power output, or put another way, the power demand reduces at any given speed as altitude increases.

That resulted in this chart, which shows the relationship in power to drag ratio (W/m^2) for speeds ranging from 47km/h up to Chris Boardman's 56.375km/h record. I've slightly amended the chart to extend up to altitude of 3,000 metres. Click on the pic to see a larger version.

Each slightly curved coloured line represents a speed as marked, and from that you can see how the W/m^2 required reduces with increasing attitude. The chart clearly suggests there is an advantage to performing such record attempts at higher altitudes, but it's never that simple of course. 

And the Physiological impact...

As we climb to higher altitudes and air density drops, the "thinner" air also means a reduction in the partial pressure of oxygen, which negatively impacts the power output we can sustain via aerobic metabolism. That loss of power can be as much as 20% or more depending on how high we go, and our individual response to altitude.

So the gain in speed from the physics side of the equation is somewhat negated by the reduction in physiological capacity. But by how much, and what might be the optimal or "sweet spot" altitude for a cyclist seeking to set a new record?

The physics side of the equation is easier to predict than the physiological, since the physics applies equally to all, however individual physiological response to altitude is quite variable, both from person to person, but also depending on how well a rider has acclimated to altitude. There are even differences in how altitude affects elite versus non-elite riders.

There have been a few published papers examining the impact of altitude on aerobic athletic performance and from these formulas to estimate the loss of power as a function of altitude have been developed. There was one from the 1989 paper by Peronnet et al, two from the 1999 paper by Bassett et al, one each for acclimated and non-acclimated athletes. Adding to those, I have generated a fourth formula, based on the 2007 study by Clark et al. The relevant papers are:

Péronnet F, Bouissou P, Perrault H, Ricci J.:
A comparison of cyclists' time records according to altitude and materials used.

Bassett DR Jr, Kyle CR, Passfield L, Broker JP, Burke ER.:
Comparing cycling world hour records, 1967-1996: modelling with empirical data.

Clark SA, Bourdon PC, Schmidt W, Singh B, Cable G, Onus KJ, Woolford SM, Stanef T, Gore CJ, Aughey RJ.:
The effect of acute simulated moderate altitude on power, performance and pacing strategies in well-trained cyclists.

Peronnet et al used empirical data from actual world cycling hour records to estimate the impact of altitude on an elite cyclist's power output. The assumptions used in estimating altitude induced power loss may have some error; in particular due to methods used to estimate the power for each rider as neither the power nor coefficient of aerodynamic drag was actually measured.

According to the old Wattage forum FAQ item by Dr David Bassett, Jr, the two Bassett et al formula were derived from earlier papers examining altitude impact on aerobic performance of four groups of highly trained or elite runners. So while these formulas were not derived from cyclists we can still generalise from those to the loss of aerobic capacity for cyclists.

Finally, the study by Clark et al measured the impact on peak oxygen utilisation (VO2), gross efficiency and cycling power output on ten well trained but non-altitude acclimated cyclists and triathletes by testing riders at simulated altitudes of 200, 1200, 2200 and 3200 metres. They examined a number of factors, including maximal 5-minute power output, VO2 and gross efficiency relative to performance at 200 metres, as well as sub-maximal VO2 and gross efficiency.

I used these data to generate a formula similar to those from Peronnet et al and Bassett et al. Of course there is an assumption of an equivalent reduction in 1-hour power as for 5-minute power. Clark et al noted slightly greater reductions in VO2 peak than for 5-minute maximal power, and no change in gross efficiency at 5-min max power with altitude. So there is some anaerobic metabolic contribution presumably making up the difference. There was some loss of sub-maximal efficiency noted at a simulated 3200 metres.

I chose in this instance to use the reduction in 5-minute power rather than fall in VO2 peak as the base data for the formula, and applied an adjustment to offset the formula for sea-level equivalency to bring it into line with the formula by Peronnet et al and Bassett et al. Of course when you look at the reported data there are of course sizeable variations within the test group at each simulated altitude, so the formula is based on group averages for each simulated altitude.

Here are the formulas:

x = kilometres above sea level:

Peronnet et al:           
Proportion of sea level power = -0.003x³ + 0.0081x² - 0.0381x + 1

Bassett et al Altitude-acclimatised athletes (several weeks at altitude):
Proportion of sea level power = -0.0112 x² – 0.0190x + 1
R² = 0.973

Bassett et al Non altitude-acclimatised athletes (1-7 days at altitude):
Proportion of sea level power  = 0.00178x³ – 0.0143x² – 0.0407x + 1
R² = 0.974

Simmons’ formula based on Clark et al:
Proportion of sea level power  = -0.0092x² – 0.0323x + 1
R² = 0.993

So how do each of these estimates of power reduction at altitude compare? Well here's a plot of these formula:

There is some variance between each formula's estimates, although the gap between the Non-acclimatised athlete estimates by Bassett et al and by Simmons based on Clarke et al is not all that large, ranging up to a ~2% variance. 

Had I chosen to use the reduction in peak VO2 for 5-min max power, then I'd expect those two lines to be closer. In any case, these data by Clark et al reasonably match earlier reported findings of the impact of altitude on sustainable aerobic power. And once again - the individual response varies - these are simply averages based on the limited data available and for the cohorts tested. As always, YMMV.

The formula by Peronnet et al is the least aggressive at reducing the estimate of a cyclist’s power at higher altitudes, and that may be due to various not insignificant assumptions used in calculating each rider’s power outputs.

OK, so now we have estimates of both the physics upside and the physiological downside of altitude, What happens when we merge the two?

Well if I recreate the chart showing the physics, and overlay on that the curve showing power output as a function of altitude, this is what we get if we examine a rider capable of sustaining 51km/h at sea level:

Let me explain how to interpret the chart.

First of all, the vertical axis scale has been changed for clarity – the slightly curved coloured lines still represent the power to drag ratio required to attain a given speed at various altitudes.

So let's examine the case for a rider capable of sustaining 51km/h at sea level.

The thick orange line represents the power to drag required to sustain 51km/h. At sea level that's ~1,800 W/m^2 (Red circle 1). The exact value depends on a few other assumptions of course, so let's just use that as our "baseline" W/m^2 value.

Now if we apply the Bassett et al formula for power reduction for an altitude-acclimatised athlete, then their baseline sea level power (and with it their power to aero drag ratio) falls with increasing altitude. This drop in sustainable power with increasing altitude is indicated by the black dotted line.

We can see the power to drag ratio resulting from the physiological impact of altitude (the dotted black line) doesn't fall as quickly as the power to drag ratio required to sustain 51km/h (the thick orange line).

If you trace the black dotted line from left to right, we can see that at Red Circle 2, the power to drag ratio crosses the line marked 52km/h at an altitude of ~700 metres. Then as you trace the dotted line further to the right, we can see it cross the 53km/h line at ~1,500 metres. Tracing the line to the right hand edge of the chart out to 3,000 metres altitude, we can see it doesn't quite reach the 54km/h line, falling a little short at 53.9km/h. So for this altitude-acclimatised athlete, they can gain an extra 2km on their hour record simply by choosing to ride at an altitude of 1,500 metres.

OK, so what happens if the athlete is not acclimatised to altitude?

This time the non altitude-acclimatised power line is indicated by the lower black dashed line. It starts at 1,800 W/m^2 at sea level indicated at Blue circle 1, but as we trace that line to the right, it falls away more quickly than for the altitude-acclimatised athlete, crossing the 52km/h line at ~1,000 metres altitude (Blue circle 2) and not reaching the 53km/h line by the time the athlete is at 3,000 metres, where in this case the athlete would be estimated to achieve a speed of ~ 52.9km/h (Blue circle 3).

So while the acclimated athlete can improve their speed by 1km/h by going from sea level to 700 metres, and increase speed by 2km/h by going up to 1,500 metres, to achieve the same speed gains the non-acclimated athlete would need to ride at an altitude of 1,000 metres and would not be able to attain a 2km/h speed gain even at 3,000 metres.

We can see that as the altitude increases, the extra speed gains begin to diminish, and there are risks in going too high, especially if you are not acclimated, or experience an above average decline in power with altitude.

Conversely, if you are well acclimated and/or have a below average decline in power with altitude, then there are benefits in going higher if maximising speed is your primary objective.

Any rider considering an hour record would do well to consider the opportunity presented by tracks located at altitude. Of course costs, logistics, regulations all factor into the choice of venue, and how much time a rider may need to acclimate to altitude, and their individual response to altitude.

If a sea level based rider were considering a fly-in / fly-out attempt without much acclimation time, then I'd suggest choosing a good track that is not too high, as the risks of a larger than expected power decline increase significantly, and the potential speed gains diminish as well increasing complexity of execution as nailing pacing gets trickier. Of course the more experience a rider has with altitude and its impact on their performance, the more confident they can be with predicting an ideal location.

So what tracks are there at altitude?

Indoor laminated wooden 250m tracks at altitude include:

• Aguascalientes, Mexico: 1,887 metres above sea level
• Guadalajara, Mexico: 1,550 metres above sea level
• Aigle, Switzerland: 415 metres above sea level
• Astana, Kazakstan: 349 metres above sea level
• Grenchen, Switzerland: 340 metres above sea level

There are track at much higher altitudes, but they are 333 metre outdoor tracks with concrete surfaces:

• La Paz, Bolivia: 3,340m
• Cochabamba, Bolivia: 2,571m
• Arequipa, Peri: 2,295m
• Mexico City, Mexico: 2,260m

Of the above listed tracks, Aguascalientes is a venue well worth considering. Eddy Merckx's October 1972 hour record of course was set in Mexico City, as were Francesco Moser's two hour records in January 1984. Most hour records since then have been set at or near sea level, with the recent rejigged rule records set by Jen's Voigt and Matthias Brändle at the Aigle and Grenchen tracks in Switzerland respectively.

So what's actually possible by the bigger guns of the sport. e.g. Wiggins, Martin, Bobridge and company?

I'll save that analysis for a future post, as well as a look at generating a formula to estimate the range of potential speed gains as a function of altitude, given an estimated sea level performance.

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W/m^2, Altitude and the Hour Record

More hour record stuff to follow on from the item on Jens Voigt's hour ride.

This time to look at the physics impact of increasing altitude. I'll layer on top of this the physiological impact in a future post.

tldr version, click on this chart:

In brief:
- for a given W/m^2, you'll go faster as altitude increases
- for a given speed, the W/m^2 required reduces with altitude
- for a given altitude, to go faster the W/m^2 required increases

Now the long version:

There are two major factors which determine the speed a rider can maintain on flat terrain such as a velodrome, that being their power output and the air resistance. Or put another way, these are the primary energy supply and demand factors. There are other smaller energy factors as well (mostly on the demand side) but power output and air resistance are by far the most important when it comes to riding an hour record attempt on velodromes (or any race of individual speed on flatter terrain).

Energy Supply

What power output one can sustain for an hour is a function of several underlying factors that I discuss in this post. We influence that primarily through training, and of course to a large extent it depends upon the genetic gifts we are blessed with*.

There is of course also the physiological impact of altitude, as the partial pressure of oxygen reduces with increasing altitude, and as a result, so reduces the power we are able to maximally sustain aerobically (with oxygen). How much reduction in power occurs with altitude is individually variable, and you can acclimate to some extent as well, but there is no denying that once altitude starts getting high, ability to generate power definitely falls away.

I go through some of this in this post on altitude training, and I will be returning to this and its impact on hour records in a future post.

Energy Demand

For hour records on a velodrome, air resistance accounts for more than 90% of the total energy demand factors. In the case of  indoor velodromes and speeds in the 50-56km/h range, it's of the order of 92-93% of the total energy demand, with the balance mostly being rolling resistance and other frictional energy losses, and a tiny fraction in kinetic energy changes. This dominance of air resistance in the energy demand is why there is such a solid relationship between speed and the ratio of power to aerodynamic drag.

Air resistance & CdA

Air resistance on a cyclist is a function of several factors, being:
- the bike and rider's coefficient of air drag (Cd),
- their effective frontal area (A),
- the speed they are travelling at,
- the speed and relative direction of any wind, and
- the density of the air.

The coefficient of drag (Cd) and frontal area (A) multiply together to give us a measure of a rider's air resistance property - CdA. A lower CdA means you can go faster for the same power, or less power is required to sustain the same speed.

CdA is something a rider can change through bike positional and equipment choices (e.g. using an aerodynamic tuck position reduces your CdA compared with sitting more upright, or using deep section wheels with fewer spokes lowers CdA compared with using shallow box section rims with lots of spokes).

So to ride faster on an indoor velodrome where there is no tail or head wind to aid or hinder, you'll need to either:

- increase your power output, or
- reduce your CdA, or
- reduce the density of air you are riding through.

Or of course some net combination of all three that results in more speed.

It is possible that one can produce less power but have a significant reduction in air resistance factors such that the resulting speed is higher. For example, sometimes there is trade off between the advantage gained from use of an aerodynamic position on a bike, even though there may be a sacrifice of some power output due to the impact the aggressive bike position has on a rider's bio-mechanical effectiveness.

It all boils down to W/m^2

Robert Chung some years ago published a nice chart that shows the equivalency of speed on flat terrain with the ratio of power to CdA:

What we can see in this chart is how well Power/CdA can help estimate speed on flat road terrain over a wide range of power outputs and CdA values. Of course it's not a perfect correlation, as you can attain a slightly higher speed with the same W/m^2 as the power (and CdA) increases. So even if you share the same W/m^2 as another rider, the rider that has more absolute power will still be ever so slightly faster.

Not by much though. As an example, if we compared two riders on a low rolling resistance velodrome, one with 400W and another with 10% more power (440W) and both had the same power to CdA ratio of 1700W/m^2, then the more powerful rider will only be ~0.1km/h or 0.2% faster (all else equal). Like I said, there's not much in it.

I also showed this in the chart from my previous post on the Jens Voigt hour ride, where estimating his W/m^2 with reasonable precision is much easier than his absolute power. If the power was lower, so the W/m^2 must be a little higher, but not by much. Over a 100W (25-30%) range of possible power outputs, the W/m^2 required to attain the same speed varies by only 2%.

So even if we consider a range of power outputs typical for elite riders of the calibre likely to attempt an hour record ride, the W/m^2 ratio required for a given speed on a given velodrome will be within a pretty tight range.

Air density

Air density however isn't quite as easy for an individual to control, as it is largely a function of environmental conditions, in particular:
- air temperature,
- barometric pressure, and
- altitude.

Air density drops with an increase in temperature and altitude, and with a reduction in barometric pressure. Humidity also affects air density, but only by a very small amount (humid air is marginally less dense than dry air). So while a rider cannot control the atmospheric barometric pressure, they can choose a velodrome with a temperature control system, or one that will likely be warm, as well as choose from a range of tracks that are at different altitudes.

Altitude and its impact on speed

So given all that, I thought I'd look at how the combined effect of the power and aero drag values required to ride at certain speeds varies with altitude. As is typical of me, I've summarised this in a chart shown below. As usual, click on the image to see a larger version.

It's not overly complex, but let me explain.

On the vertical axis is the ratio of power output to the coefficient of aero drag x frontal area (CdA). Power / CdA in units of watts per metres squared.

On the horizontal axis is altitude in metres.

Then I have plotted a series of slightly curves lines, one each for speed ranging in 1km/h increments from 47km/h to 56km/h, and another line for 56.375km/h, which is the speed Chris Boardman averaged for his hour record.

For the sake of comparison, I've fixed the air temperature, barometric pressure, bike + rider mass and rolling resistance to be constant values for each. I did a little variation of power, but not much, and as I have demonstrated, the impact is very small.

So if we look at any particular line, we can see how the W/m^2 required to sustain that speed reduces as altitude increases. And of course we can see that for any given W/m^2 the speed you can sustain varies with altitude.

e.g. let's take 1800W/m^2. At sea level, the 1800W/m^2 line crosses the 51km/h line. As you trace horizontally from left to right, the 1800W/m^2 crosses the speed lines roughly as follows:
51km/h @ sea level
52km/h @ ~500m altitude
53km/h @ ~1000m
54km/h @ ~1450m

55km/h @ ~1950m

56km/h @ ~2450m

So naturally there is interest in using tracks at higher altitudes in order to ride faster and set records.

Now of course different tracks have variable quality surfaces, and so the assumption of rolling resistance being equal at all tracks is not valid, so any comparison of actual tracks should also consider impact of changes to coefficient of rolling resistance (Crr). Even so, since Crr accounts for only ~ 5-6% of the total energy demand, then track smoothness, while a factor, is more important when considering tracks at similar altitudes.

But what about power output at altitude?

Well of course there is a trade off between the speed benefit of lower air density at increasing altitudes, and the reduction in a rider's power output as partial pressure of O2 falls.

Hence as altitude increases, while a rider's CdA will not change, their power output will fall and hence their W/m^2 will also fall accordingly. So the W/m^2 line for any individual won't be horizontal, but rather trend downwards from left to right.

How quickly an individual's W/m^2 line drops away with altitude then determines the real speed impact of altitude.

So, what's the optimal altitude for an hour record?

I'm going to explore that in a future post (although I'm certainly not the first to have done so). So stay tuned.


* Pithy Power Proverb: "Choose your parents wisely".

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The Mile-High Club

Following is an item I first wrote in March 2010 but it never made it onto my blog - so here it is for the record!

Will “altitude training” help make me a faster cyclist?

I was asked about this a few times recently, and while it seems a fairly straightforward question, the answer is less so. The short answer is “it depends”. There are several methods of altitude training, and many circumstances under which it may (or may not) be applicable, and the impacts on our bodies and endurance cycling performance varies widely.

So anyone who is using or contemplating the use of some form of “altitude training” should do some basic research to firstly define what is meant by it, as well as under what circumstances the application of such training may be beneficial (or indeed detrimental) to endurance cycling performance. So to help kick start that thought process, following is an introduction to the topic.

What is Altitude Training? 

The basic idea of “altitude training” is to train and/or live in a hypoxic environment (lower than normal/sea-level partial oxygen pressure), either by actually being located at high altitude, or by simulating the hypoxic conditions experienced at altitude.

It can also include the use of methods to raise the partial oxygen pressure (hyperoxic training) either by use of supplemental oxygen in training, or training well below sea level (there are places it’s possible). I won’t expand further on the use of hyperoxic training in this post.

Hypoxic (high/higher altitude) conditions have an acute detrimental impact on cycling power output. So why would we use it? 

Well the theory is that exposure to a hypoxic environment stimulates the body’s various systems (pulmonary, cardiovascular, endocrine, skeletal muscles) to respond and adjust in an effort to provide enough oxygen to survive and that these physiological responses may also enhance endurance athletic performance. It is an area of physiological and exercise physiology research that has been widely studied.

How does one do Altitude training? 

Exposure to a hypoxic environment is achieved in several ways, commonly (but not exclusively) through:

• Actually living and/or training at altitude. This doesn't really apply to most of Australia (or other “low land” countries), although we do have some places popular for training camps with moderate altitudes from 900-1800 metres.
• Training and/or living in a semi-enclosed atmosphere controlled environment (e.g. “altitude rooms” or “altitude tents”) with either: 
• hypobaric hypoxia (where the barometric pressure of the air is reduced, thereby lowering the partial oxygen pressure), or 
• normobaric hypoxia (where the barometric pressure is normal but the proportion of oxygen in the air breathed is reduced, usually by increasing the proportion of nitrogen).
• Use of “face-mask” connected to a devices that delivers hypoxic air (Hypoxicator). 

Of the above, only being in a location at altitude allows you to train outdoors, the other two require training to be performed within controlled environments on an indoor cycling trainer/ergometer, since the enclosures and equipment are not readily portable.

What types of altitude training are there? 

Altitude training comprises three broad methods, although there are several variations on these basic themes:

• Live high, train high
  this may be beneficial as a unique early-season overload and also when preparing for competition at altitude. 
• Live high, train low
  can be specifically used to enhance sea-level performance 
• Live low, train high
  may be useful for enhancing sea-level and altitude performance 

The above three methods typically require a significant proportion of time spent training and/or living to be done in a hypoxic environment. Even so, not all research supports the use of such training; nevertheless, there is sufficient evidence to support its considered use by well trained athletes in specific circumstances.

The combinations can be achieved by some who live in geography that enable these options, or via the use of simulated environments while living high or low.

Another option becoming available is the use of devices to enable:

• Intermittent exposure to hypoxia (IHE) / Intermittent hypoxic training (IHT) 

These IHE/IHT devices (typically a face mask connected to a hypoxicator device) are sometimes used on an occasional basis, for relatively short time periods (e.g. once or twice per week for an hour or two while cycling on an ergometer / indoor trainer). However the evidence to support the beneficial performance impacts of such IHE / IHT is equivocal and not supportive of such a method.

To quote Dr David Martin (Senior Sports Physiologist, Australian institute of Sport):

“For those selling devices that allow the athlete to experience IHE, much anecdotal information is cited. It may be tempting to believe that changes in resting hematocrit, haemoglobin and performance after a period of IHE substantiate the effectiveness of this technique. However, rapid changes in plasma volume known to occur after exposure to altitude can explain elevations in hematocrit and haemoglobin without a true increase in red cell mass. Additionally, a placebo effect or a training effect generally can explain improvements in performance. Thus, available evidence does not strongly support the use of IHE”. 

Dr Randall Wilber (sports physiologist at US Olympic Training Centre in Colorado Springs and author of the book: Altitude training and Athletic Performance) also says the following:

“It is unclear whether IHE or IHT improves red blood cell count and haemoglobin production despite increments in serum EPO. Data are equivocal regarding the claim IHE or IHT enhance VO2max and endurance performance in well trained athletes”. 

Should I consider using altitude training? 

When deciding whether and what type of altitude training to use one also needs to consider for each individual, the:

• Current state of fitness and/or whether they are rehabilitating from injury 
• Time of season 
• Type of events being targeted and when 
• Altitude of events / competition being prepared for 
• Duration of hypoxic exposure 
• Unique response to hypoxia (everyone is affected differently and strategies need to account for that) 

As with all things fitness related, if you haven’t already sorted the basic fundamentals of improving athletic performance, then you should not view altitude training as a “magic bullet”. The best way to improve performance is through good training, good diet and ensuring sufficient recovery.

Even when training at altitude, these fundamental principles still apply, indeed much more care needs to be taken as there are many additional impacts that altitude training may create that need to be managed (e.g. heart rate responses; hydration levels; carbohydrate metabolism /glycogen depletion; iron levels; immune system; oxidative stress; exposure to UV light; sleep recovery disturbance; and altitude sickness). Power (or HR) training levels will need adjustment and everyone’s responses are different.

 Some scenarios for which one might consider the use of altitude training include:

• Athletes preparing for events/competition at altitudes significantly above where they typically live and train
• A cyclist who is already very fit and requires a novel overload
• An athlete seeking to enhance sea-level or moderate altitude level performance and has several weeks available for altitude exposure 

Pithy Power Proverb:

The best use of altitude training is when preparing for competition or other riding at altitude. 

How long does it take to attain an improvement and how long do performance benefits last? 

Athletes will need to consider exposure to hypoxic conditions for several weeks. Studies have shown at least four weeks exposure to altitude is required if one is expected to derive associated haematological and muscle buffering benefits.

And this exposure needs to be a minimum of 8 to 10 hours per day.

As to how long beneficial effects last, well if one remains at altitude then they will of course maintain their adaptations accordingly, provided basic training fundamentals are followed. As for returning to sea-level, then this is highly individual and varies widely but studies have shown the beneficial effects may last for up to three weeks post-altitude.

How does altitude affect power output? 

Courtesy of Charles Howe (thanks Charles), below is a chart that summaries the effect of altitude on sea level aerobic power, as modelled by various sources as shown in the chart legend:

We can see there have been various attempts to assess the impact of altitude, and there are substantial differences between the various models. The same sources were used in the following table, which I summarised from the (now no longer available) Wattage forum FAQ:

“The effects of altitude on the volume of oxygen uptake (VO2max) and hence aerobic power are highly individual, so it is difficult to predict to what extent any one person will be affected, although as a general rule it has been shown that elite athletes, as compared to normal individuals, have a greater decline in VO2max under conditions of reduced ambient pO2 (partial oxygen pressure). This is caused by their higher cardiac output, which results in a decreased mean transit time for the erythrocytes (red blood cells) within the pulmonary capillary, and thus less time for equilibration between alveolar air and blood in the pulmonary capillary”. 

The range of impact to aerobic power varies upon altitude, individual fitness levels, whether one has acclimatised and other factors. Different research studies have found performance is impacted as follows (but individual response varies):

Sources: 
via old Wattage FAQ site (now no longer available - archive.org link provided instead):

https://web.archive.org/web/20070129084754/http://www.midweekclub.ca/powerFAQ.htm#Q17

Bassett, D.R. Jr., C.R. Kyle, L. Passfield, J.P. Broker, and E.R. Burke. Comparing cycling world hour records, 1967-1996: modeling with empirical data. Medicine and Science in Sports and Exercise 31:1665-76, 1999.

Peronnet, F., P. Bouissou, H. Perrault, and J Ricci. A comparison of cyclists’ time records according to altitude and materials used. Canadian Journal of Sport Science 14(2):93-8, June 1989.

More information? 

The details of how and when one should consider the use of these training techniques and all of the specific issues to consider is far beyond the scope of this post. For those interested in reading further about the topic, there are a couple of very good chapters on the topic from two excellent references which cover the science and research specifically applicable to cycling, and from which I drew much information in this post:

• Professor Asker Jeukendrup’s book, High Performance Cycling, includes a very helpful chapter by Dr David Martin on the subject.
• Dr Edmund Burke’s book, High Tech Cycling, the Science of Riding Faster, has a detailed chapter by Dr Randall Wilber, specifically investigating the use of altitude training in preparation for competition at sea level.  

As well as an entire book on the subject by Dr Randall Wilbur: Altitude Training and Athletic Performance.

These are by no means the only available summaries or information on the research and scientific literature and new studies are published at times - a quick search on PubMed will locate many references. However the above should provide more than enough information for anyone to make sound decisions about how and when they should consider altitude training, and in what form.

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