cbr shadow wrote:
Iâ€™ve read some of the discussions about indoor vs outdoor FTP differences, and it sounds like cooling is the biggest factor.
I generally use TrainerRoad during the week (3-4 workouts) plus 1-2 outdoor group rides on the weekends. I use a Computrainer indoors in TrainerRoad and have the FTP set to 254, which is where I tested doing a 20 minute indoor FTP test 10 weeks ago. The workouts did seem to start getting â€śeasierâ€ť (still tough, but nothing insane). I planned on retesting my FTP sometime soon but have been avoiding it a bit.
Recently I bought PowerTap P1 pedals that Iâ€™ve been using outdoors. Theyâ€™re calibrated and working great. I went for a long ride, about 60 miles with 4,000â€™ of climbing which ended with a really long climb, so I decided to do a 20-minute FTP test just to see what Iâ€™d get. My legs werenâ€™t fresh but I decided to try it anyway. In that test I averaged 295 watts for 20 minutes. Based on that I should have a 281 FTP, correct? That makes me really happy, especially since I went into it with fatigue in my legs.
I feel like there are a lot of factors though:
1) Cooling outdoors is better than indoors
2) Computrainer indoors VS. Powertap P1â€™s outdoors
3) I havenâ€™t tested FTP in 10 weeks and have been riding consistently, so maybe I just made gains
So, whatâ€™s my FTP???
Should I restest on the Computrainer to verify? Argh those 20 minute tests are tough. My end goal is to make sure my indoor FTP is set correctly so that I can get those most out of my indoor sessions.
You are spot on with you analysis of possible discrpencies between indoor computrainer power and outdoor P1 power. Since power measurments are not 100% accurate, a large part of the discrepency can come from the power meters themselves. Is it possible to put your P1 pedals on the bike you use with the CompuTrainer? In TrainerRoad, we can use the power from the pedals to control the CT via PowerMatch, allowing you to eliminate one of the variables.
Other than that though, it can be hard to estimate your FTP without doing a test. Your actual FTP should be the same regardless of whether you are indoors or outdoors, however as you mentioned, the temperature and humidity indoors may effect your body's ability to express high percentages of FTP- therefore you may not be able to simply use your outdoor FTP of 281. If you are looking for a "quick and dirty" way to assess your fitness you could choose to just do one of the 8 Min test intervals and multiply the result by 0.9. While not perfectly comparable to your 20 min test from before, it can certainly give you an idea your progression without the pain of a 20 min test.
You could also choose to continue with your indoor training and increase your FTP by 3% and see how that feels. If you are still able to easily complete all your workouts, maybe add another 1-2%. If that's too much and you can't finish your workouts, back it down a little bit. This method allows you to go by feel and listen to your body. While not as scientific as periodic testing, it will ultimately lead to similar results in applicaition.
I hope this helps! Let me know if you have any more questions :)
Get Faster with TrainerRoad