Struggling with high cadence to meet target Watts

General Discussion
1

Hi,

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?

Thanks!

2

Hi Robert,

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.

Just play with the actual gear yo are using.

BR Marcel

3

Hi Marcel,

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.

4

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.

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5

Hi Lebasi,

Thanks for your answer, sounds good - I will try that tonight and see how it goes!

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6

Hi,

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.

Thanks for your help

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7

This is the way. :sunglasses:

8

Glad you got the hang of it! Hope your training goes well!

9

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.

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10

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.

11

I did a search for this very question. The higher the wattage and cadence I’m at, the closer they seem to get to matching goal, but otherwise, I could not get both of these numbers in the same zone even after I stopped and recalibrated. I find myself wanting to switch gears to make it happen, though I know I’m not supposed to have to. (Wahoo KICKR). “Specialized” brand bike.

We just updated my KICKR to the correct speed KICKR (11 to 8) for my bike last night with appropriate spacer and I recalibrated it after a couple times. Some gears just don’t ride as smoothly feeling crunchy on my chain and I find myself not wanting to leave it there though that’s the spot to calibrate it well.

Newbie could use some tips here.

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12

25 watts seems too low for a warm up. Have you done an FTP test?

From my experience in ERG mode when the watts required in warmup or cool-down are too low it’s difficult to smoothly maintain the required watts without going above the target. You can end up spinning your legs off too easily.

It’s inevitable that it’s necessary to tweak the indexing of the shifting to make it run smoothly on a trainer. I’ve never had that match the wheel of a real bike properly. Always ended up with noisy operation unless I spend time adjusting the indexing of the shifting. That’s easy enough with Di2 but it’s a pain with mechanical group sets.

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13

Thank you! I couldn’t sleep thinking about it and was glad to see an answer in here with some things to consider.

I haven’t done FTP. That was my goal yesterday, but the shortest test was 45 minutes long!
A. I wasn’t sure my bike was set up correctly for it
B. I’m still getting used to my bike seat again and REALLY can’t ride that long. I’ve probably ridden it too much to start out and could only handle 15 minutes yesterday.
C. It looked SUPER intimidating!
D. I wasn’t really sure of the difference between FTP and a ramp test.

I guess I can just stop when I max out. That makes sense now that I think about it.

I tried to make my own shorter FTP test - one with some intervals for recovery, but I don’t know where it saved, couldn’t find it after I spent all the time doing it, and then realized it wouldn’t accomplish a true FTP for program purposes anyway.

So, I was getting tired overthinking and just did a “fun and easy” ride so I didn’t damage anything on my bike til I figured out what the heck I was doing. But not being able to hit goals was frustrating me. If I can’t accomplish both should I focus on watts or cadence?

——-
don’t know much about bike gear and chain maintenance yet. The closest bike store is an hour away, so I’d have to leave my bike at least a week and go back to get it. So…I really need to learn some things. We’re pretty handy but I know this can be tricky and skill level helps.

My husband already worked on the derailer position, it was rubbing after we switched out the KICKR gears.

lt was still feeling ”crunchy”, so he tightened the chain a bit, oiled it, but the main gears I need to be using to accomplish calibration are the worst, and I assume I need to leave it in those where I am able to calibrate it? I can find smoother gears, but they aren’t letting me stay in goal zones.

He said it’s not rubbing anywhere.

I need to explore which of the two types you mentioned that I have.

This is way more than I knew before, so thanks! I had too many questions to move forward and I want to keep going while my motivation is high.

14

Do a ramp test instead, that will be much shorter. It will still be hard but not a long effort.

The ramp test result is usually multiplied by 0.75 to get a rough FTP.

So if you get up to 400w for last minute then that’s 400w x 0.75 = 300w FTP.

In all my experience with a lot of ramp tests either my own or with other riders that’s a reasonably accurate result that can be used for FTP.

The older style mechanical group sets have a steel shifter cable connecting the shifters to the derailleur. Old school and “simple” so they say. Well yes, simple but the cables stretch, they can fray and get jammed up and they seem to alway need adjusting.

Electronic shifting, either Di2, EPS or SRAM E-TAP does away with that altogether. More expensive, batteries can go flat and potentially electronic cables can break but usually far more reliable.

15

I’d say “it’ll give you an OK place to start looking for your FTP” …

… especially if Joan follows it with the Zone Benchmarking workout to triangulate with RPE (rate of perceived exertion)

16

Good advice. I found a shorter 8 minute FTP test today. That gave me somewhere to start. Did my first fitness workout tonight and had an unusual first round spinning out to reach goal wattage, exhausting myself so I decreased bias 10% and got a great workout on a smooth middle gear. Lost ERG ANT+ at one point and had to disconnect and reconnect it but otherwise things went great!

(I have the mechanical type bike.)

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17

That sounds like it worked out properly. :slight_smile:

With the erg workouts it shouldn’t be necessary to change gears, just find a smooth running middle gear combined with the big chain ring should be fine and keep turning the pedals smoothly, letting Zwift control the resistance for you.

With a new FTP it will always be difficult for a few weeks until you get used to it.

The next steps are to let the recovery happen, so schedule in easy days and you should see improvements coming over time.

18

In my experience, erg mode tends to work best in the little ring, because reduced flywheel inertia means that the resistance changes are much snappier, without overshooting the target power.

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19

When the Watt target increases, do not change how you pedal. If you see a message on the screen telling you to increase power, ignore it. Just keep pedaling at your preferred cadence and wait for the trainer to respond. It may take some time for that to happen but you can’t make it happen by increasing cadence, you just have to wait for it.

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20

You highlight here one of the dumbest things on Zwift - the message telling you to increase/decrease power if you’re in a workout on a smart trainer.

That message should not appear if you’ve paired with a smart trainer. It should only be for trainers without ERG mode.

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