Knee pain and Erg mode - correlation or causation?

Sorry for another knee thread, but I can’t find anything with significant discussion on the impacts of Erg mode.

I’ve had a knee issue, that comes and goes, for a few years now. Always the same knee, always the same spot. I’ve been through physio and still, it remains.

I’ve always been an adamant Erg user for anything that involves long intervals because I like to watch tv while I ride. For the last few months I’ve been doing various traditional base work with Erg turned off, and for the first time in a long time, haven’t had much knee pain, even when doing 2.5 hour indoor rides multiple times a week. I assumed this was because I was doing all Z2, but an interesting thing happened to me today. I was doing a SS ride, the first one in months, and I had no pain. I switched into Erg for the cool down, and almost immediately sensed the pain. Turned it back off, and almost none.

Am I mistaking correlation for causation? Or have others noticed nagging knee pain that goes away when switching off Erg?

First question is about gearing. Are you using the same exact gearing when switching between trainer modes?

In general, I would say no, because you have to shift when not in Erg.

OK, then that is a variable the must be considered.

When you use Resistance or Standard modes, you can adjust the values of those up or down, and that will impact the functional gearing used to hit any power level. It parallels the whole “gearing / inertia in ERG” discussion we have had for years.

So, within reason, especially if you are working on “efforts” at a level and gear in ERG, you can tweak those RES/STD settings to be using a similar gear in them, like you did in ERG.

That would be my first recommendation and test, in order to eliminate one more variable. As of now, there are at least two here (trainer mode & gearing) and either or a combo could be related to your issue.

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Are your cadences the same in both modes?

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Also a great question and variable to consider! :smiley:

I get the same thing when I ride indoors on ERG for extended periods - it’s not always in the exact same spot, but just some generalized joint soreness that I never get outdoors, even for rides with identical power/intervals. When I do indoors rides without ERG, I don’t get the pain. My take on it is cadence - i bet your cadence stays much, much more consistent indoors on ERG than other scenarios. When this happens, the repetitive stress is too much, and it causes pain.

I know there are a thousand different people who will chime in with their N=1 stories, but this is the story for me.

Definitely, yes

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Definitely a good point, but in this specific case, we’re talking about 30 seconds and it appeared

I think I feel similar and put it down to the resistance being tweaked in erg mode, if I am tired it brings my natural cadence down. Having to overcome those micro tweaking up of the resistance takes its toll on me for longer intervals.


Somewhat related, we see just enough “ERG mode did this…” comments and claims, I started working on what may be an outline for testing and consideration.

This still has a looong way to go, but is worth a look to see the variables I have documented already, when looking to compare trainer modes (and maybe plenty more?) for situations like this. I work on it occasionally, and can add more whenever people recognize issues or ideas I have not addressed.

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When I first started with ERG I think my FTP might have been a tad on the high side I was getting dragged into the spiral of death too often which could lead to knee grinding. At the time I proffered 100% resistance mode where I wasn’t dragged into the spiral of death. I think my FTP is set to a better level now and I can avoid the spiral of death or pedal out of it. That has seen me do work outs more evenly in both ERG and resistance mode. What is still a pain if I stop pedaling before I start so I can easily press the laptop touchpad to select a workout out. ERG will ramp the resistance up so I tend to do a couple of minutes warm up now before I even start TR so I’m ready to pedal out of it, again the lower FTP helps (or I toggle to Resistance).