I’ve seen similar queries, but haven’t found a satisfactory answer; hopefully someone can help out.
I have a Tacx Neo Smart Bike. I’ve been casually exploring Zwift, cruising about, and looking at my stats, my cadence seems around 90 on average.
I just started a training plan, and the first session is Zone Benchmarking. This is in ERG mode, so my understanding is that I don’t change gear as the resistance is automatically adjusted.
There were 2 issues, one, I found it hard to maintain a consistent wattage; my cadence was ranging between 100-105, but the watts were bouncing from 200-240 or so and I was struggling to meet the target.
More concerning was the cadence required to hit the higher wattages, 110 for Zone 5 was just about manageable, but 130 for Zone 6 was way too much. I could just achieve it - the target Watts was 300W.
When I ride freely and adjust the gears I have no trouble holding 400+W for a minute, but there is no way I can get close to that in ERG mode, my legs just don’t spin that fast.
How does this work? I read that TdF sprinters achieve maximum Watts at a cadence of 115-125. Why am I doing 125-135? And I’m not even close to my maximum watts.
So, the question is, what am I doing wrong. I just use regular shoes for cycling, no clips. Is my FTP too low, i.e. does Zwift demand 125-135 RPM at Zone 6 and adjust the resistance so that it will achieve the required Watts? Even then the RPM is very high. Is there something else?
It’s essential what gear you are using with ERG mode.
I assume you use a common (road or mtb) cassette. Why my recommendation would be to choose a medium gear for the ERG mode.
My experience is, smart trainers could adjust the desired power (which is technically a result of speed and torque against the trainers resistance) only in a certain speed range. The actual speed at the trainers axle is then decisive.
This fact becomes a problem when you have intervals that vary between 150W and 700W for e.g. in the same workout.
Thanks for the reply. However I have a Tacx Neo Smart Bike, it’s a purpose built trainer, not a bike, so no cassette.
I can change gear, but it’s just electromagnets doing some stuff I think.
Hi Robert,
If you’re not used to ERG mode, it can take some getting used to to figure out.
In ERG mode you need to hold your cadence at whatever target you have for it for a bit to allow your smart bike/trainer to adjust the resistance to produce the desired wattage. If you spin faster when prompted to produce higher wattage in a workout then it will reduce the resistance required to produce that wattage
Assuming that there’s nothing wrong with your equipment, it should work as follows in the description from Zwift Insider Insider.
"In Erg mode, your trainer’s job is to make you hold a particular wattage. “Erg” comes from Greek “Ergasía” which means “work”. Erg mode is literally forcing you to work at a particular level.
Example:
Your Zwift workout interval wants you to hold 200 watts for 10 minutes
If you are spinning at a cadence of 90 and putting out 200 watts, then slow your cadence to 60, your trainer will quickly increase resistance so you are still holding 200 watts even though you are pedaling slower.
If you are spinning at a cadence of 90 and putting out 200 watts, then increase your cadence to 110, your trainer will quickly decrease so you are still holding 200 watts even though you are pedaling faster.
Erg mode simplifies your workout, so your only job is to manage your cadence. You don’t need to worry about shifting (although it is certainly allowed), or whether you are hitting your wattage target. You just need to keep your cadence where you want it, and the trainer will make sure you’re hitting the target power."
If you’re already holding your cadence steady, then it could be an equipment problem or something else. But if you’re not, you might want to try experimenting as stated in the example above.
I tried it this evening, and I got the hang of it. Also, the info messages on this training session (ramp test) explained it. Maybe i missed some key messages on the first ride (zone benchmarking).
I think the tactic is to completely ignore all the red flashing watts numbers and focus on cadence, because for me the watts bounce around a bit, often below the target, and when I see that I’m tempted to push faster to increase the watts. But, if i just focus on cadence the watts take care of themselves.
Having completed my first week of a training plan, my original problem was symptomatic of the first training session, Zone Benchmarking, which was described as an intro session. Interestingly, it was also scheduled as the 6th session of the week, so I got to relive it.
I can see why it confused me. Unlike the other training sessions I did this week, there was no cadence guidance in it at all, none of the messages described maintaining cadence and letting the machine control the power. Yet, Power (Watts) is the main metric mentioned and displayed, with messages such as “Increase Power” and “Decrease Power”.
Without understanding ERG, this sounds like I’ve got to change something. The guidelines in this session said to not change gear, so the only thing I can change is cadence. But the point is that I shouldn’t change anything at all, I should maintain consistent cadence and let the machine work.
Really, the screen messages should be “Maintain steady cadence” or something.
The messaging for that training session is poorly thought out, if it’s used as the first training session for someone new to ERG training.
Anyway, I’ve got the hang of it now, so I can enjoy and benefit from the sessions.
Yep, those messages about Increase/Decrease Power are nonsense if you have a smart trainer, and only make sense if you were on a dumb trainer where you need to manually increase the resistance.
