# TrainerRoad vs PowerTap FTP Training Questions



## kilgoretrout (Dec 16, 2013)

I use TrainerRoad's virtual power during the winter. I have the Kurt Kinetic trainer which they say provides pretty accurate power readings. But in a month, I will have my very first PowerTap. Prior to this, when outside riding, I just trained by heart rate zones that I gathered from the TrainerRoad FTP tests which I did inside on the trainer. 

So I'm wondering a few things:
1. Can I use the FTP I have from TrainerRoad and apply it when out on the road with the PowerTap? Or will my FTP numbers be way off?

2. If the TrainerRoad and PT number are off, then can I mount my PT bike up to the trainer to do an FTP test? Or do you have to do FTP tests outside with the PT wheel in order to ensure accurate testing? 

3. I've never done an FTP test outside, but I know the ones I do on my trainer basically crush me. So how the heck do you do one out in the real world and expect to not just fall over after you are done? Or manage to pedal back to where you started?


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## Cervelo S-5 (Dec 16, 2011)

kilgoretrout said:


> I use TrainerRoad's virtual power during the winter. I have the Kurt Kinetic trainer which they say provides pretty accurate power readings. But in a month, I will have my very first PowerTap. Prior to this, when outside riding, I just trained by heart rate zones that I gathered from the TrainerRoad FTP tests which I did inside on the trainer.
> 
> So I'm wondering a few things:
> 1. Can I use the FTP I have from TrainerRoad and apply it when out on the road with the PowerTap? Or will my FTP numbers be way off?
> ...


Hi Kilgoretrout, I train in a similar fashion myself and do not have a PT either. I use 2 trainers, a KK like yours when I want to monitor the power with the trainer road programme, and the other is a Tacx flow that I can use either on a slope setting for resistance or a power setting that can be held constant. 

I would use your TR FTP to start with as you know the perceived effort pretty clearly and if you were trashed, then you probably did it right. It should be pretty easy to check the two meters (virtual vs. PT) by simply setting up tour test again, or even just a workout with the same parameters on the trainer (very important to consistent with tire pressure and resistance) and run the course. The TR will show you a graph that you can compare with the graph that comes from the data recorded by the receiving unit of your PT and you will have an idea of how well they pair pretty quickly with the same perceived effort and heart rate. 

Depending on what test you do, (and I think that Alex Simmons out there helped me to get this THANKS!) remember that it is most accurately a measure of the FTP for the length of the test. The 20 min test on TR is good and an accepted method but is based on a calculation to get the FTP for 1 hr. Use your PE and HR as a guide to judge the accuracy of the two when comparing, but remember that there are a lot of variables with these. Hydration, fatigue etc will all play a role in HR and even your own PE estimate. 

IMO the best 1 hr FTP measure is and all out 1 hr test after a good warm up and that can be done with both meters on the bike running for comparison under the same conditions. Ensure that you are well rested prior to doing this and use it as one of your hard efforts for the week. Regardless of the #'s what you are after is improvement with the same efforts under the same conditions. Later you can take these perceived efforts out on the road and check the #'s with the PT of course understanding that now there are different external parameters (wind, road smoothness, inclines, potholes, idiots) that are not there in the perfect world of the trainer.

After two seasons of fairly consistent winter training on it, I have found that the effort required on the KK trainer is actually harder (@3 full turns after contact and 100PSI) than the flat road resistance, and the Tacx flow is quite a bit easier based on the length of time that I can sustain high wattage and speeds on it. It just about kills me to sustain 35-36 km/h for long periods of time on the KK (about a 70 min 40 km ITT) yet out on the road I can be sub 57 min (42 km/h).

Good Luck!


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## Alex_Simmons/RST (Jan 12, 2008)

kilgoretrout said:


> I use TrainerRoad's virtual power during the winter. I have the Kurt Kinetic trainer which they say provides pretty accurate power readings. But in a month, I will have my very first PowerTap. Prior to this, when outside riding, I just trained by heart rate zones that I gathered from the TrainerRoad FTP tests which I did inside on the trainer.
> 
> So I'm wondering a few things:
> 1. Can I use the FTP I have from TrainerRoad and apply it when out on the road with the PowerTap? Or will my FTP numbers be way off?
> ...


1. Use the PT's power numbers. You will no longer need to rely on "virtual power" if you have a power meter. Just make sure to zero the torque on your power tap before each ride, and perhaps a coast every so often to allow auto-zero function to do its thing thereafter.

2. Put the PT on the bike on the trainer, and then do training based on the PT's data. 

3. Testing outdoors just needs a suitable venue where you can ride hard contiguously for the intended duration/distance, and in safety. That may or may not be possible depending on where you live. It might require a little travel to find a suitable location.

Keep in mind that your ability to generate power indoors on trainer may not be the same as it is outdoors, with the former often resulting in less power than the latter (but not always). So base your training on what you can actually do in the environment in which you are training.


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## hrumpole (Jun 17, 2008)

The only thing I will add is that the relationship (n=1) in difficulty tends to be fairly constant. Thus, if FTP=220 outside, indoor FTP will be 200, indoor vo2 (120 percent FTP) will be 240, etc. YMMV.


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## Nevermiss (Jun 7, 2011)

I would add that for me, I've found that the CTS field test and the 20 min FTP test yield very similar FTP calcs and the CTS only requires two 8 min. efforts.....yeah....I'm lazy like that (I'm sure the full test has been discussed on this thread somewhere).


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