What happens to a Zwifter’s FTP when he packs up his family, cat, 4 bikes, and turbo trainer and drives 2000 miles (3200 km) and more importantly down a mile (1600m) to sea level?
I am lucky enough to live at the base of the Rocky Mountains in Denver CO, USA at an elevation of 5470 feet (1667m). I was also lucky enough to stay at two beach houses in Massachusetts, USA (both elevation ~100 feet/30m) for a 4 week period in August and September.
Background
My training FTP was at 266 prior to the trip, and I was about halfway through the Crit Crusher training plan when I packed up. I paused training for riding in beautiful Massachusetts and informal Zwifting. I did, however, do weekly FTP tests.
The Tests
For all tests I took the Ramp Test as this seemed to be the easiest repeatable test.
Just prior to leaving I took a test on the bike and trainer I would be using for the trip. My FTP was up to 274 (+3%).
My first week at sea level and not riding (4 days of driving will do that to you) my FTP rose to 275 (a whole Watt gained). This unexpectedly small gain was due at least in part to not be acclimated to the humidity and poor ventilation.
Note: Denver is extremely dry with humidity below 50% and my pain cave is in an air-conditioned basement. My setup in the living room in Massachusetts was 90-100% humidity with no air conditioning and only a small fan.
My initial setup in the living room in Massachusetts 
A more ideal setup
One week later, I was able to raise my FTP 282 (+3%).
After a couple more weeks I was able to find an ideal setup and time to test in the morning so I could take all the caffeine I wanted. Also, I was able to scream as loud as I wanted. Plus I used PR Lotion. I raised it to 288 (+5%)!
Then it was back to Denver: FTP took a nosedive to 257 (-11%)! Ouch! The good news is I got it back to 266 (-8% from peak) a week later:
Other Riding
While I focused primarily on riding outside, I did ride a few non-test rides on Zwift. Two in France (route hunting), one in NYC, and an Alpe Du Zwift ride. In general, I felt more powerful and tired less easily. For instance, I did my 2nd best time up the Alpe the day after an FTP test, just missing the hour mark.
What about racing? Sorry, I don’t regularly race on Zwift and did not do any races while at sea level. I would love to hear anybody’s experience with this.
Conclusions
Clearly, elevation makes a difference in your FTP. Based on my experience (be wary of anecdotal evidence) going to sea level gave me about a 5% boost in FTP. Coming back cost me about 10%. This seems in line with what others have found (See “The Effect of Racing at Altitude” from TraininPeaks). This would be enough to move me from an upper category C to lower category B rider.
Could Zwift give at elevation riders a boost to level things out? Certainly they could check your location via the Companion App. Should they? Probably not worth the effort given the small number of riders at significant elevation and the likelihood someone would hack it to get an unfair advantage. Just give me a Ride On when you see me cruising around Watopia.
I also live in Denver. Had an opportunity to test this out about a month ago when I was in Del Norte (+3000 feet in elevation) for a week. Significantly reduced performance in my weekly ZRL race that I think lined up pretty well with the Training Peaks article you referenced.
It does make me pause and consider how training mostly in Denver should be approached for a race in Leadville or other higher elevation areas. It’s very real though and I would suggest no one underestimate the effects of elevation!
Yes. I ride the Iron Horse Bicycle Classic and Triple Bypass, 10k+ elevation is significantly harder.
Nice – I’m considering the Triple Bypass this year. If I do, I suppose it would help to schedule some training rides higher up in the mountains.
Seems likely, as they talk about the impact to sports teams when they go to play in Denver. Away teams from sea level tend to have a tougher time playing. This also explains why the USA Olympics Team have training facilities in Colorado Springs.
Live in Denver as well. Before moving here 8 years ago, I spent a few weeks here checking things out. My riding buddies on the east coast always trained all winter (I didn’t at the time), and always dropped me like a bad habit until I got my base fitness back in the spring. But just by spending 2 weeks in Colorado, not even riding or anything, when I got back I was so much stronger and was able to hang at the front with everyone. I felt like Superman, for a few weeks anyway. I came back down to… Read more »
Does Elevation affect power? Sure. Does a bad day at work affect power in a race? Sure. Where do you draw the line? Unless now we want to start normalizing every single 500,000 Zwifter’s power based on altitude. Right now, we don’t even know whose trainer is throwing out watts representative of their actual fitness. Frankly, normalizing inaccurate numbers based on altitude will be an extra level of dum.
No evidence that having a bad day affects performance or even how you can measure or quantify such a thing. Elevation adversely affecting performance is well proven. Not a valid comparison to prove or bolster any argument.
I agree compensating for altitude generally is a bad idea. In particular, the affect on different power levels differs. For example, sprint power, which isn’t limited by O2, may not be affected at all. It could be a “FutureWorks” option if race promoters wanted to use it in selected events, but for standard events, it should just be about watts.
MAYBE wind resistance could be adjusted for rider altitude, although this would provide another opportunity for cheating.
I’m not a racer at all, but I’ve been curious about this for a while just from a human performance perspective. I live in Colorado at 7,300 feet and always wonder what it would be like to suddenly be riding at sea level. Thanks for posting about your experience.
Also live in denver and have a place in Fraser about 3200′ higher. I notice about a 20 watt difference when at altitude.
I totally feel it when XC skiing any Devils Thumb
I put my altitude (8682′) in parenthesis in my user name so I might get a little sympathy when I get passed.
Zwift Insider posted a link to an Alex Dowset TT ride earlier in the week. In this video he stated that he was at altitude and explained how this would affect his power output. Well worth a watch. I think he said it was 15%
I have no experience with altitude but it would be interesting to test it one day.
I’ve been living and racing at about 1600m for the last 10 years or so but I was born and had always lived at sea level before that in various countries. I still get caught out sometime in races indoors and out doors if I go above aerobic threshold too far. A couple of seasons ago I raced back at sea level for a major race and it was great – I felt so good and really put in a good race helping our team leader win and coming in the top 5 myself. I have been told that cars… Read more »
Waves from Erie, CO 👋
Hakan
I dunno how you ride on a wooden floor like that with an FTP of nearly 300w, if I did a sprint I’d prolly be worried about going straight through the floorboards XD
My experience is from road running. I had run a hilly 5 mile race near home in the UK, perhaps a few hundred feet above sea level, with a time of 27.20. A few weeks later work took me for 2 weeks in Colorado Springs, but on the middle weekend I drove to Denver for another 5 mile race. It was similarly hilly, but I found myself gasping for air while my legs wanted to go faster – I even walked a few yards on the final climb, which was pretty unknown to me. Final time was 30.20, so a… Read more »
You may be losing it now, but just remember: when the ice caps melt at least you’ll still be above the water while the rest of us are trying to cycle underneath it, lol 😁
Let zwift adjust the drag coefficient based on your location due to differences in air density. It’s the trade off that the riders going for the hour record make. Oxygen v drag in the altitude debate. #Notaserioussuggestion
I dream of one day Zwifting in a compression chamber that brings my relative air pressure closer to sea level. I live in the foothills outside of SLC (~5,180′) and the impact of lower O2 is completely discernable, but perhaps the easier thing to do is host meet-ups with local riders. Considering how many riders are on Zwift these days, it might even be reasonable to start scheduling regional races for riders from Denver/Alberquerque/Salt Lake can race on somewhat even terms.
Great idea
Have a heart for those of us that live UP in the Rockies! My primary home and much of my Zwifting are in Breckenridge at 9,800′ (~3,000m). We also have a place in Denver and I do some riding at sea level, but have been on Zwift at sea level only in early 2019 Nevertheless, I have ridden Alpe du Zwift at all three locations and my times/average power up the Alpe probably provide the clearest illustration of altitude impact on me. Houston Feb 2019 – 242watts, 55:20 minutes Denver Nov 2018 – 226watts, 58:46 minutes Breckenridge Jun 2019 –… Read more »
Have a heart for me when I ride in Summit County :p
Thanks for the numbers, seems pretty similar to my experience.
I live in San Francisco (see level). I went to Park City Utah (2200 meters) for a month. My powers were down around 20%. The most notable effect was the ability to recover from anaerobic efforts (I went from basically no recovery @ beginning of trip, to better at end of the month). Upon returning, my power bounced back to where it had been (I got a boost in ability to sustain power > 20 minutes, but my 20 minute power was about the same). I was surprised by the large effect (20%). This is basically a full Zwift category.
I just did a similar elevation related test. At home at 8363ft my ftp was 287.
At 16ft my ftp went to 307.
Tests were done 5 days apart and both on the ftp test (shorter) program, both 20 minute efforts.