Understanding FTP Estimate

How long was the test minus warm up?  Your FTP is the wattage you should be able to maintain steady for an hour.  Was the test this long? 

Hey tess,

The test is Garmin's guided test, it stopped itself after 16 minutes, I was mistaken about the last ramp being 3 minutes, it was 4.

You went in with an FTP estimate of 184, the result was 183W, and that is inplausible????

Garmin's Guided FTP test is not a test to exhaustion, so your Perceived Exertion seems about right. Instead it is designed to generate enough data below and above threshold to identify the change in heart rate variability that is typically associated with threshold. It's more an LTP, than an FTP.

Cycling maximumHR is typically slightly lower than running maxHR. The heart rates you achieved are consistent with this. 

I find the results I get from Garmin's Guided FTP test are 10-15W lower than what I can get from the 20 minute steady state method. 

Hey mcalista,

I wrote inplausible as I expected a difference because I felt that the test was easier than it should be. I get the idea of LTP and thank you for the explanation. Would it then be better to train based on Garmin's lower estimate or is it preferrable otherwise?

I like that the Guided Test isn't to exhaustion, and leaves me less fatigued. So I test with this more often.

I use the 20 minute method perhaps a couple of times a season, but use the changes from more frequent Guided testing (every month or so) to adjust that. 

How about when following a training that suggests for example a certain % of FTP? Wouldn't the standard estimate be a better use for improvement?

A few things that you did not mention that I want to verify just to be sure. Did you calibrate the power meter before starting the test? If you aren't doing that, you should be doing that every time you start a ride using a power meter. Power meters are basically strain gauges and measure deflection of a thin piece of metal inside the meter. The sensors are very sensitive and so even changes in temperature can affect readings which is why it is important to run the calibration each and every time. My Garmin Edge computer prompts that every time I start a bike activity and the power meter is detected but from what I've seen the Fenix does not. You have to manually do that each time before starting the activity.

Second, is your previous FTP of 184W done on the trainer or on another power meter? While power meters may be individually precise, they may have variations in side to side comparison that while doesn't ultimately matter for training purposes does make direct comparison only useful if you are comparing relative changes in FTP over time.

So, unless you are going at your FTP for 20 minutes or more, it really won't feel super hard. It shouldn't either because it's an effort that you could sustain for 60 minutes. Therefore, if you sustained your FTP for 60 minutes, then your TSS would be 100, basically an all out 60 minute effort. Given that, your TSS sounds about right.  Looking at where your heat rate was at each ramp rate, the FTP doesn't seem really wrong to me. As far as which one to use, basically you only had a one watt difference which for all intensive purposes is zero. So for training purposes the difference isn't going to change your power training zones enough to matter. It usually will take in my experience a +15 to 20 watt increase to really feel the difference.

Some people might say that the best test for your FTP is to do an actual one hour test. However, we have to figure out why we are doing the test in the first place. Is it to truly find our best one hour time or establish meaningful training zones for the purpose of getting fitter and faster? Since most for most people it's the latter they often use the 20 minute test. The problem with the one hour test is that it becomes not only a test of your physical power, but mental power. That has a place but not for setting training zones. The 20 minute test is still a mental test as well so there have been other tests developed such as the Garmin one and the 8 minute test that Carmichael Training Systems has used for years. That is one that I've used to good effect. So I would try using the Garmin test and see how it goes with using it to set up your training zones. If you are consistent with your training and see meaningful changes in your FTP with the Garmin test each time you do it, you are good to go. However, I wouldn't do the test more than every four weeks at the most, probably every eight weeks is fine. It's takes a while to build up significant changes in FTP unless you are starting from completely out of shape. The only time I might deviate is if starts becoming very clear that it's gotten significantly easier to hold the same wattage than when you last tested your FTP.

Lastly, I've noticed and experts have noticed that a person's FTP indoors is typically lower than the FTP they can achieve outside on the road. There has been a lot of speculation on this but it seems like the most plausible reason for this is temperature. Even with the best fans, you can't quite mimic the cooling effect that you get from riding outside and the theory is that since your body can't dump heat as efficiently your power level drops.

Hey LJ,

You got a good point I did not calibrate my trainer. I did not know they were that sensitive. The estimate was done on the same trainer earlier this year. My question earlier wasn't about which one to use between the 183 or the 184, rather should I rely on another FTP test to set my training power zones (such as Zwift, or Elite's app guided test, a 20 minutes by myself, etc.) which is expected to be 10-15W higher as mcalista mentioned.

I'll follow your advice and stick with the Garmin test, see how it goes and if I remember I'll update this post with more info for other people having the same issues.

Thank you!

Ah, I got you. Sorry for the confusion. Yeah, I would just stick with whatever test you like so that you can make meaningful relative comparisons over time. I'll be curious if after you calibrate, or zero offset the power meter as it is also referred to, makes a difference in your numbers. Even if it does, it doesn't mean that you didn't give the right amount of effort, your heart rate numbers reflect that you did. However, unless you are really light, your FTP seems a little off given your stated VO2 max, even if its from Garmin and not a lab tested one. I'll be curious to see what results you get after trying to calibrate your power meter.

LJSkywalker74 said:

your FTP seems a little off given your stated VO2 max,

Careful with statements like this as a VO2max is not directly related to power. A high VO2max only indicates the maximum amount of oxygen a body can use during exercise. It is not a direct indication of power or pace. FWIW, my VO2max has remained pretty constant around the mid-40s (I am 64) for a few years now but my pace at VO2max has decreased as I’ve had a number of injuries and do not have the muscular endurance or strength I once had. However, it appears that my cardiorespiratory has not been affected very much.