My N=1 experience with living and training at sea level, then going to race Ironman Lake Tahoe at 6000ft was that I lost about 20% of my power for equal perceived effort and measured heart rate.

In other words my HR and perceived effort showed I was riding to plan, but my power was 20% lower than expected.

I can't say if bigger people are more affected by it than smaller people though.

I actually was able to run a "test" on this on the very climb that Dumoulin and Quintana will climb tomorrow 5 weeks before IM Tahoe 2015.

Here is what I did. i left Bormio riding at 220-225W. This should have been 85% of my FTP. I calculated the climb from Bormio to the summit of Stelvio should have taken me around 1:30 to 1:40 so I needed to target a power that I could easily sustain at sea level for much longer. I had already done the Muskoka 70.3 at 227W NP that year. I wanted to get some benchmarks on what would happen to my power at Tahoe. So off I went. From 4500 to 6000 feet, 220-225W seemed easy enough. Not crazy hard, but not sucking wind either. At 6000 feet, I was just below IM Tahoe altitude. Once I got above 6500 feet, 220W was hard to hold. My breathing was getting laboured. It did not feel like 85-90% FTP, more like 93-95%. Soon I was at 7500 feet (which would be around the highest in Tahoe) and my perceived exertion exploded. It felt like 100% FTP. I managed to keep up the watts but from 8000 feet to right under 9000 ft, it felt like I was now riding at 105% FTP, when my power number was still at 220W down at 85% sea level FTP, but it felt like 105%.

My weight for this climb was 138 lbs, so a bit heavier than Quintana (and dramatically lower wattage).

For an Ironman, I normally ride right around 180W average. For IM Tahoe, I did 165W and split 5:37. As a point of reference off 182W at IM Whislter, I went 5:29. This is my experience on that very climb that the Giro uses tomorrow, doing a "power test benchmark".

I tend to feel that smaller athletes should be less affected by altitude, only because the people of this earth that have settled in high altitude have adapted with smaller overall sizes.

Plenty of smaller people adapted for living at near sea level as well in tribes across the globe. Probably as much to do with availability of nutrition than altitude per se.

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I think it is widely known that you do lose power at the same RPE at higher altitude. Having raced up Haleakala 5x, I can attest that even when I have started conservative and finished strong, my last 45 minute power (at 8000'+) is still about 12-15% lower than the first 45 minutes.

That said, I have not heard that larger athletes would suffer from the power losses more at altitude than smaller athletes. Another thing to possibly consider is if the cooler temperatures at higher altitude may give a more of a benefit to larger athletes who can generate more power than the smaller athlete without as much of the over heating penalties they may experience closer to sea level.

I'd be really curious to learn more about this. I have a well-established personal dataset of my performing at about 10% less than expected power on higher-altitude TT course I've done 6 consecutive years. The first couple years I thought it was just a bad day. But it's very consistent. My competition also suffers from some power loss, but seemingly much lower in magnitude than my own from looking at their data and just my relative performance against them on this course vs. other courses.

I have no idea if it's size or some other factor, but I am larger at around 175lb. But I have some competitors who are bigger than I am who seemingly don't have an issue.

Losing power at altitude is probably considered well established. Larger athletes being effected more, not sure about that.


* 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., G. Thibault, and D.L. Cousineau. A theoretical analysis of the effect of altitude on running performance. Journal of Applied Physiology 70(1):399-404, 1991.


https://www.trainingpeaks.com/...-racing-at-altitude/

power at altitude will be diminished by a certain percentage. It is individual to some extent, but there are some good ranges (bell curve) for most people.

Lets say for the argument that its 10% power loss. Tommy D lets say has an FTP of 440 watts. Quintana has a FTP of lets say 360 watts. so Tommy D loses 44 watts.. Quintana loses 36 watts.

Tommy D normal W/kg (157 lbs, 71.36 kg) = 6.16
Tommy D at altitude = 5.54

Quintana Normal W/kg (128 lbs, 58.18 kg) = 6.18
Quintana at altitude = 5.56


This calculation would indicate no real change... but this is just using rough calculations based off wikipedia weight and assumptions of FTP for both riders.

Now.. if someone loses say 8% and another loses 12%.. then we have a large swing in performance.

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COROS Sports Science

Typically 4-8% power loss going up to 5000 feet and then about 1% more for every 1000 feet.

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Mike Ricci
2017 USAT World Team Coach
USAT National Coach of the Year
Coaching Triathletes since 1992.

It's been a couple years but my best crack at the Mount Evans Hill Climb, I avg'ed just under 289 watts for 1:50 and was struggling to hold 240ish at the top. That said it was a mass start race with some tactics being played out as I was riding for a teammate until he went solo but starting at 7500 ft and climbing to over 14000 ft, well it's almost depressing to watch the watts evaporate.

240W is phenomenal at that altitude and duration of prior effort.

You're right...no real change...
But neither has an FTP remotely close to your numbers...both would need to be running a crit approaching 60 to get those numbers.

Right, I'm asking about the latter. Guess i should have been more clear.

if you are a bigger rider then you would generally generate more watts so if everyone loses 10% a bigger rider would lose more watts. If all the other variables are equal (and thats a big IF) a bigger rider needs as many watts as they can get to keep their mass going so it will definitely impact them more.

Uh, not really. For a start it's not about watts to "keep their mass going".

If we consider the two primary resistance forces in play, gravity and air resistance:

For hills - the same proportional loss of power (or reduction in W/kg) will mean both are equally affected on ascents. No gains for either there.

On flat terrain, for example two 4W/kg riders, one that's 75kg and another that's 60kg who both experience a 10% loss of power will see the lighter rider gain an advantage of less than 1/10th of a second per kilometre.

The light rider might gain 10 seconds for an IM bike leg or less than a 0.1% speed benefit relative to their heavier buddy (due to the physics alone).

In context of all the variables involved, that's essentially no difference.

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http://www.cyclecoach.com
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I would expect those numbers to be close. Why do you feel they aren't? Just curious

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COROS Sports Science