One training comment really caught my eye. THE LAP COUNT: Some people argue that Boulder is an awkward altitude in that you’re not quite getting all the benefits possible. Does it feel much different than when you were in Flagstaff?
Scott Fauble: I think 5,000 feet is much easier than 7,000 feet. But one thing Joe [Bosshard] has been into is this thing called “altitude density” with like the pressure in the air, given if it has rained, the temperature, and stuff like the barometric pressure changes. Altitude training is basically just a measure of pressure.
This fall he’s always been saying, “it is a low-altitude day!” As opposed to the summer when it’s hot, you’re getting more high-altitude days and you run slower. I don’t care that much about altitude since I was born at it.
Can someone explain this to me what he's talking about? How much does the temperature really impact it? It sounds like they are saying based on the pressure of the air some days feel like lower altitude days. I get that the density of warm air is less in comparison to cold air but how much does that really change how much oxygen you are getting?
I assume you run slower in the summer becuase of the temperature - it's hot people, not because the air is less dense and their is less oxygen. Thoughts?
He's confusing barometric pressure (which varies with the weather) with partial pressure of oxygen. Given a constant altitude, the partial pressure of O2 should stay about the same.
Pilots have known this for decades. You need a longer runway to take off on “high altitude days”. Most coaches at altitude are aware of this. Joe doesn’t ever come up with anything new.
Altitude density is an important thing in aviation.
Definition Density altitude is pressure altitude corrected for temperature. In layman's terms it directly affects the performance parameters of any aircraft, and in effect it is the equivalent altitude of where, performance-wise, the aircraft “thinks” it's at. The higher the density altitude, the lower the aircraft performance, and vice versa.
Example: So if you start your plane in Flagstaff at 6909ft on a cold winter morning, it needs less runway to get airborne. On the other hand, if it's 105F in Flagstaff, he might not get off the ground at all.
I am not sure if that exactly translates to running but that's the explanation.
Definition Density altitude is pressure altitude corrected for temperature. In layman's terms it directly affects the performance parameters of any aircraft, and in effect it is the equivalent altitude of where, performance-w...
I'm from colorado springs, barometric pressure is real. You can kind of notice across state results in XC that some specific days (across many courses) are PR days, this is generally because there was favorable barometric pressure. You don't feel it, but its obvious when looking at times.
I assume you run slower in the summer becuase of the temperature - it's hot people, not because the air is less dense and their is less oxygen. Thoughts?
They’re does seem to be something to question here
When you live under the shadow of Pikes Peak, it\'s easy to think it\'s all about elevation. It turns out that it\'s more complicated than that. Colorado Track XC file photo.
With that background information in tow, let's go back to the example of Potts Field in Boulder (actual elevation 5260 feet above sea level) to illustrate how barometric pressure and temperature impact density altitude. Our calculations will ignore the small impact of relative humidity.
On a day where the adjusted barometric pressure is 29.71 (inches of mercury) and the temperature is 75F at Potts Field, the density altitude is 7703 feet. On a day where the adjusted barometric pressue is 30.02 and the temperature is 63F, the density altitude at Potts Field is 6628 feet. On a day with an adjusted barometric pressure of 30.36 and the temperature is 49F, the density altitude at Potts Field is 5369 feet.
I'm from colorado springs, barometric pressure is real. You can kind of notice across state results in XC that some specific days (across many courses) are PR days, this is generally because there was favorable barometric pressure. You don't feel it, but its obvious when looking at times.
I think to prove this, you demonstrate a strong correlation between barometric pressure and times on these courses. Otherwise it's just bro science.
This is a common thing to consider in automobile racing as well. A change in temperature/barometric pressure/humidity (besides track temperature, but lets ignore that) will significantly change the performance of a race car, due to the density of air the engine intakes as well as the impact the change the air density will have on the cars aerodynamics and downforce in corners. Even in F1 racing, some cars will be more competitive relative to others in higher density air vs. low density air.
You can also see the effects in baseball - lower density in the summer allows for less movement on pitches and the ball to travel further when hit towards the fence. Colder temperature come playoff time allows for more movement on pitches and the ball to travel less far.
Pilots have known this for decades. You need a longer runway to take off on “high altitude days”. Most coaches at altitude are aware of this. Joe doesn’t ever come up with anything new.
Seems more like a dewpoint issue. I am at sea level on the Gulf Coast. In the winter, when a cold front moves through and high pressure builds in behind it, temps in the morning are in the low 40s and dewpoints are very low. That always means piles of PRs at the races. But when temps are in the upper 50s to 60s and it is cloudy and humid, PRs are more scarce and more people are bonking. And those conditions are always under low pressure due to an approaching front pulling warmer and more moist air off the Gulf.
With that background information in tow, let's go back to the example of Potts Field in Boulder (actual elevation 5260 feet above sea level) to illustrate how barometric pressure and temperature impact density altitude. Our calculations will ignore the small impact of relative humidity.
On a day where the adjusted barometric pressure is 29.71 (inches of mercury) and the temperature is 75F at Potts Field, the density altitude is 7703 feet. On a day where the adjusted barometric pressue is 30.02 and the temperature is 63F, the density altitude at Potts Field is 6628 feet. On a day with an adjusted barometric pressure of 30.36 and the temperature is 49F, the density altitude at Potts Field is 5369 feet.
It's a good article, but density altitude is not a useful concept for interpreting distance running performance. That's because it is not the decrease in atmospheric density that primarily affects human respiration at altitude, but the lower partial pressure of oxygen (PPO2).
At a fixed temperature, these two variables would move together (see the ideal gas law) and density altitude would just depend on barometric pressure. Indeed, as long as you stick to the ISA standard temperature used as a benchmark in the density altitude formula (15C), there could be some validity to using density altitude as a scale or intuition for the effect of barometric pressure (and the resulting differences in PPO2) on distance running performance.
However, very little of the variation in density altitudes discussed in the MileSplit article, or that Bosshard talks about, are driven by differences in barometric pressure. Outside of extreme weather scenarios, barometric pressure typically varies by only 1-2% (though it could drop by as much as 20% in the center of a tornado - don't try to set a PR in the center of a tornado!) Rather these differences are overwhelmingly driven by temperature.
Obviously, temperature does affect running performance. But it does so through different mechanisms than altitude, limiting our ability to dissipate heat rather than to get oxygen. So thinking of this in terms of density altitude - the hypothetical altitude that would have the same atmospheric density at 15C and 29.92 Hg as your actual temperature/pressure combination - just isn't useful.
Just to further clarify this last point, since I think it's the main point of confusion in the linked MileSplit article (and possibly with Bosshard): Hotter air is less dense, but this in itself does not affect our ability to extract oxygen from the air. Instead it's the partial pressure of oxygen that matters, via the rate of gaseous diffusion across membranes in the lungs, and this is independent of temperature. For example, see this article: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1114067/ Key quote: "At high altitude [...] the alveolar-arterial difference for oxygen is higher than would be predicted from the measured ventilation-perfusion inequality. This is because the decreased driving pressure for oxygen from alveolar gas into arterial blood is insufficient to fully oxygenate the blood as it passes through the pulmonary capillaries. This is more evident on exercise as cardiac output increases and blood spends less time at the gas exchanging surface (diffusion limitation)."
In conclusion (thank you for coming to my Ted Talk) - the concept of density altitude is misleading when applied in this way, because it conflates changes in atmospheric density, which don't affect oxygen exchange, with changes in the partial pressure of oxygen, which do.
Final sidenote - density altitude could actually be a useful concept for sprints! That's because it is indeed the atmospheric density which is relevant to drag forces.
With that background information in tow, let's go back to the example of Potts Field in Boulder (actual elevation 5260 feet above sea level) to illustrate how barometric pressure and temperature impact density altitude. Our calculations will ignore the small impact of relative humidity.
On a day where the adjusted barometric pressure is 29.71 (inches of mercury) and the temperature is 75F at Potts Field, the density altitude is 7703 feet. On a day where the adjusted barometric pressue is 30.02 and the temperature is 63F, the density altitude at Potts Field is 6628 feet. On a day with an adjusted barometric pressure of 30.36 and the temperature is 49F, the density altitude at Potts Field is 5369 feet.
It's a good article, but density altitude is not a useful concept for interpreting distance running performance. That's because it is not the decrease in atmospheric density that primarily affects human respiration at altitude, but the lower partial pressure of oxygen (PPO2).
At a fixed temperature, these two variables would move together (see the ideal gas law) and density altitude would just depend on barometric pressure. Indeed, as long as you stick to the ISA standard temperature used as a benchmark in the density altitude formula (15C), there could be some validity to using density altitude as a scale or intuition for the effect of barometric pressure (and the resulting differences in PPO2) on distance running performance.
However, very little of the variation in density altitudes discussed in the MileSplit article, or that Bosshard talks about, are driven by differences in barometric pressure. Outside of extreme weather scenarios, barometric pressure typically varies by only 1-2% (though it could drop by as much as 20% in the center of a tornado - don't try to set a PR in the center of a tornado!) Rather these differences are overwhelmingly driven by temperature.
Obviously, temperature does affect running performance. But it does so through different mechanisms than altitude, limiting our ability to dissipate heat rather than to get oxygen. So thinking of this in terms of density altitude - the hypothetical altitude that would have the same atmospheric density at 15C and 29.92 Hg as your actual temperature/pressure combination - just isn't useful.
Just to further clarify this last point, since I think it's the main point of confusion in the linked MileSplit article (and possibly with Bosshard): Hotter air is less dense, but this in itself does not affect our ability to extract oxygen from the air. Instead it's the partial pressure of oxygen that matters, via the rate of gaseous diffusion across membranes in the lungs, and this is independent of temperature. For example, see this article: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1114067/ Key quote: "At high altitude [...] the alveolar-arterial difference for oxygen is higher than would be predicted from the measured ventilation-perfusion inequality. This is because the decreased driving pressure for oxygen from alveolar gas into arterial blood is insufficient to fully oxygenate the blood as it passes through the pulmonary capillaries. This is more evident on exercise as cardiac output increases and blood spends less time at the gas exchanging surface (diffusion limitation)."
In conclusion (thank you for coming to my Ted Talk) - the concept of density altitude is misleading when applied in this way, because it conflates changes in atmospheric density, which don't affect oxygen exchange, with changes in the partial pressure of oxygen, which do.
Final sidenote - density altitude could actually be a useful concept for sprints! That's because it is indeed the atmospheric density which is relevant to drag forces.
thank you, i was cringing so hard on that post rojo liked so much.
almost a given if rojo think something is brilliant it's actually garbage.
most people think altitude is slower because there is less oxygen in the air. That is WRONG
There is more than enough oxygen in the high altitude air to fully oxygenate the blood but the issue is that the lower atmospheric pressure causes lower partial pressure of oxygen which means less oxygen transfers from the lungs to the bloodstream.
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