I added 20W to my threshold.....
......by just going to sea level.
How does altitude affect power output? | Two Wheel Blogs
Feet Meters % FTP
0 0 100%
1000 300 99%
2000 610 98%
3000 910 96%
4000 1220 95%
5000 1520 93%
6000 1830 92%
7000 2130 90%
8000 2440 88%
9000 2740 86%
10,000 3050 83%
11,000 3350 81%
12,000 3660 78%
13,000 3960 75%
14,000 4270 72%
You can use this table to figure out what wattage you can produce, or what your FTP will be, for whatever altitude you're headed for. Just divide your current FTP wattage by the %FTP percentage corresponding to the altitude you live at. Then multiply that number by the %FTP percentage for the altitude you'll be riding at.
Suppose you live at 3000ft. and you'll be riding at 10,000ft. Your FTP is 300watts. To get your equivalent FTP for your ride at altitude, the first thing you do is divide FTP by the %FTP for 3000ft.:
300 / 96% = 312.5
Now multiply this number by the %FTP for 10,000ft.:
312.5 * 83% = 259watts
Your power output at altitude will roughly correspond to an FTP equivalent of 259 watts.
Understanding significant figures
I'm afraid you're putting way too much reliance on the precision of this relationship. Different people will respond to altitude changes in different ways. I would guess the error of the estimate is at least +/- 20%.
Originally Posted by Poncharelli
Going from Salt Lake City (~4500 feet) to sea level, I usually see roughly a 20-25 watt increase in my sustainable efforts (a little bit more for shorter efforts, maybe 30 watts for 5 minutes or less)
It's always interesting seeing how different people react and adapt to changes in elevation. For me I always feel like superman on the first day of a sea level ride, but then have a problem with sore muscles the next day. It usually takes my body about a week to adapt to the increased ability to produce torque/watts.
Sometimes I find it hard to race at sea level with having lived at moderate altitude my entire riding career. I am too trained to be cautious of overreaching in an effort (since you WILL pay for it at altitude, in the form of a spectacular explosion ) and it takes me a little while to be more daring in how hard I push.
From my experience, the chart is pretty accurate for a 2000 - 3000 foot change in altitude, according to the PM.
For large changes, there probably would be large error for some individuals.
Chase, unfortunately I'm not as well traveled with my bike as you are.