I just finshed Galena which is ”just” 3x20 minutes just below threshold. As time passed my HR went really high so in order to finish the workout I geared down to the small ring. Now, I keep the power target, TSS according to the workout is reached. But my HR dropped, the ”speed” dropped almost 20 km/h and my general RPE dropped slightly. Now to my question, does this ”trick” while in ERG mode mean that the workout I got gave less in terms of fitness gains as if trying to gut it out in a higher gear (which I modt likely would not have managed)?
Just to be clear…when you went to the small ring your cadence went up or down? At the same power a higher cadence will usually yield a higher HR (more emphasis on the cardiovascular system) than a lower cadence. How this interacts with erg mode I don’t know as I don’t use it.
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Basically the same cadence, slightly above 95 RPM.
You can achieve the same power at a low cadence (muscular) and high cadence (aerobic). Over a 20 min effort and expecially late in the workout you will prefer one over the other. Generally, as the muscle fatigues you will lean towards a higher cadence just to keep less pressure on the pedals, or at least this is the case for me. As long as the power is met and the cadence is not extremely high or low (relative to your normal racing/riding) then you’ve still achieved all the goals of the workout. You didn’t cheat your way through the ride.
Depending on the trainer, flywheel and inertia, etc ( bunch of tech stuff I don’t understand) RPE May have changed.
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What trainer?
Tacx Flow.
As I understand it, when you’re training with power in erg mode, gearing has limited impact on your success.
Harder gearing (same power target) engages your muscles at higher rotational positions (say 12 o’clock) using certain leg muscles, and creates more flywheel speed which may feel more road-like and conditions more high-twitch muscles fiber with higher aerobic capacity.
Easier gears (same power target) use a few more leg muscles and engage earlier (say 10 o’clock), with more slow twitch fiber (call them power fibers) which is driven by your glucose system, and creates less flywheel speed resulting in less speed.
Same power workout, slightly different training results.
Somewhere in all this is a matching of cadence to resistance that feels better and allows me to push hard without blowing up on big intervals. When I’m doing 4 to 6 intervals I try to adjust my gearing up or down on 2 intervals to try to benefit from both of the above. I like to run in harder gears for my over-unders.
M
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Thanks for all response. I suppose the mantra ”Power is everything” still holds? I was a bit worried I was cheating (however, my legs tell me I wasnt…)
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Since I got my Kickr Core I noticed the exact opposite as you. I did Hunter today and split the work between small ring up front and large ring up front all while averaging 90rpm and not only did I find the large ring easier on my muscle fatigue my HR also dropped. I feel like the higher spinning flywheel makes it so much easier it’s almost like cheating. Just for reference when I was doing the same workout on my fluid Kinetic I pretty much stayed in the small ring the entire time because shifting to the large ring was just about impossible to do unless out of the saddle.
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In ERG mode, gearing generally has a big impact. As @Tezz observed, big ring is easier due to flywheel inertia, especially on a wheel-on trainer such as a Kickr Snap.
I did a test with the same over-under workout done with alternating blocks of intervals on 50-14 and 50-16. Because I was right on my limit I noticed (for the same 95 cadence) a higher effort and higher heart rate in the lower gear, even though it was only two cogs different.
On Trainerroad, in ERG mode, you can effectively have a “small ring FTP” and a “big ring FTP”. The latter will be higher than the former. So, yes, it’s a way of cheating your way to a higher FTP number.
The analogy on the road is that It’s like changing the gradient (and therefore the effect of inertia) from flat (big gear) to uphill (low gear).
There’s two possible reasons here - with the first I think being a lot more likely than the 2nd.
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You find low inertia/speed riding (small ring) easier than high inertia/speed riding (big ring). This is true for me also. Others, however, report the opposite. This likey is due just to different physiologies between riders.
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Your trainer (or power meter) measures power differently bwteeen high inertia and low inertia riding. This would obviously be a flaw in the power measurement, but there is an analogous case where power meters can vary in terms of power they measure - oval vs round chainrings.
The reason this is analogous is because the angular velocity of the crank over the pedal stroke varies differently between low inertia riding and high inertia riding. Same is true between oval vs round chainrings.
I’ve not seen any confirmation of this (ie different power measurement between big vs small ring), so I guess this will remain just a theory until any evidence emerges.
Same thing happens to me in TR, in Zwift, and while (my) Tacx Flow is being controlled by Golden Cheetah. Hence I conclude that this is most definitely not a software issue. And I’m pretty sure this is an estimation* bug.
Until I get an actual power meter and use that to measure watts I will just settle with doing workouts in the large ring (which feels -and is- noticeably harder) in order to maintain consistency (albeit not -as it seems- validity)
*the Tacx Flow does not have a true power meter, so some sort of estimation is being carried out in the unit
You have a wheel-on trainer, while I have a direct drive (Wahoo Kickr).
I also find RPE easier in little chainring, and have posted about it:
Ignore the speed. Really not sure if RPE translates fitness gains. What I will say is that the little chainring provides gearing that requires less force / torque to respond to resistance changes. That much is true. Everything I’ve read about inertia so far is speculation.
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I just did a 2+ hour flat “Coffee ride” in little ring, at 0.95 intensity with a lot of time pulling. The interesting thing is that RPE felt easy… reinforcing my comment that little ring gearing makes sudden accelerations easier because it requires less torque/force. Similar to what I’m feeling on the trainer.
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