Lower than target power during interval training


I’m brand new to Trainer Road. I did my first power test two days ago and my first ride, Haku, this morning. There were 6 x 20 second intervals. I’m using a CompuTrainer with the Mac legacy app. I trained today in ERG mode.

My target power for the intervals was 394. I spun up to 120-125 rpm well in advance of the interval as recommended, and I maintained between 120 and 130 rpm during each interval.

I felt good. I thought I was executing the training well, but looking over the results, my actual power for the intervals was about 354 each time, 40 watts below the target. Is this just the lag for ERG mode to catch-up? Am I actually getting the desired training load because there is a lag in the power drop as well?

Any information or advice will be greatly appreciated.


Please post a link to your workout or a screenshot of one if the intervals on the graph. I suspect I can explain. but want to make sure my guess is right.

Hope this link is correct. If not, please let me know how to grab the link (sorry, newbie).


Thanks for your help!

It might be, but your workouts are set to private, so it doesn’t do us any good.

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Well, here is my guess as to the issue. In short, don’t look at the Interval Summary data, because it misses the start and end values from lag.

TR aims to fix this a bit by sending the resistance change 1-2 seconds early, but some jumps are still missed. If you look at the actual time around the target power (even if it doesn’t align with the blue blocks) you are probably getting the full effect of the training stimulus.

O.k. just fixed that. Thanks for letting me know.

Thanks so much! I’m hoping that’s the case.

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Yes, it’s the thing @mcneese.chad said.

TR is computing average power for the intervals by looking at when it expects the interval to be. If your trainer lags the expectation a bit, that offset makes the average power over the interval “wrong”.

If you look at the analytics graph, though, you can see this – the bulk of the interval matches up just fine with the target power, but the transitions on to and off of the interval are offset a little bit.

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