- Yes. Any time that you change your power measuring device, you should retest with that new device.
The reason is that despite manufacturer claims to precision, there are distinct differences in power measurement between most power devices (power meters and trainers included).
It is common for people to feel that that workouts are “easier” or “harder” after adding a new power device, when they have not reassessed their FTP with the new device. This happens because their new device reads higher or lower than the prior one.
Using PowerMatch helps set the trainer to the right power target to match the reading of your power meter, but it does nothing to actually “fix” the differential from your prior workouts/tests from the older device.
Say that trainer gave you and FTP of 200w.
- You do workouts at that level and everything is fine.
Then you add a power meter, and lets say it reads at 210w when your trainer is at 200w.
- If you use it with PowerMatch, the trainer will be reading 190w when the power meter says 200w.
- As such, you are getting a 10w easier resistance when compared to the power from the trainer only, at your 200w FTP.
That is an over-simplified example, but actually quite typical. The differences can be higher or lower, so the “feel” to the rider will vary based on that difference.
To reiterate, you should always retest whenever you get a new power measuring device.