Workout (ERG) mode & perceived exertion

Just wondering if it’s just me, or a known phenomenon. I seem find it way harder to keep up with both the higher intensity intervals in workout mode than in the normal mode. Even Z2 and Sweetspot intervals, that I normally do for fun, are a real challenge.

I’m using the Tacx Vortex Smart with a Rotor Power Meter. I checked to make sure the power readings come from the power meter, as I’ve found that the Tacx usually reports 10-20w less power. Knowing the power readings come from the right power meter, I pretty sure the perceived exertion doesn’t come from having to output more power.

As said, I’m curious what your view is

Erg mode is a double edged sword.  It’s great for steady state efforts as it allows you to ride at a consistent wattage while settling in at your preferred cadence.  I find it can become a disadvantage, however, when doing work above threshold.  When doing intervals outdoors, your power output drops as your cadence drops (all else being equal).  In ERG mode, the trainer is trying to maintain a consistent wattage for the duration of the interval regardless of cadence.  So as your cadence drops, the trainer is still holding the watts set for that interval where outside you can either gear up or spin slower.  I find 300 watts way easier at 90 rpm vs 70 rpm.

ERG mode is also implemented differently across many smart trainers.  I find that some are much better and more ‘natural’ feeling than others.


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i have been experiencing the safe phenomenon on the Tacx Vortex. I was really struggling around FTP for more than a minute or so… starting to wonder if my FTP was getting worse whilst on the FTP building workout plan :frowning:

I was doing a 2X20 today and had to stop. I could not hold  my FTP for more than 5 minutes. MY HR normally stays around 140 AVG as soon as I started a 20 min block it shot uo to over 160 and the resistance was too much.