Erg mode for short and sharp intervals


#1

I’m just in my second month of using Trainerroad and once I finish SSBI, I’ll be starting SSBII next week. I’ve had a quick look at the workouts in SSBII and a few of them such as Ebbetts and Clark seem to have short micro-burst intervals of 5 seconds or 12 seconds. I’ve been using erg mode for all of the workouts in SSBI and had no problems so far.
Should I continue using erg mode, or will the trainer struggle to ramp up the resistance and back it off for such short 5 second intervals? And if no to erg mode for these workouts, should I be doing the whole workout in resistance mode, or just switch to resistance mode before the short intervals?

I’m using a Tacx Neo and Trainerroad on a Windows PC.


#2

Plenty of people will tell you different than me, so take a look at the variety of responses you get but…

In my experience these efforts on workouts like Bays + 1 seem to work fine for me with a Kickr Core and power match to my powertap pedals.

Because of how steep the ramps are you don’t always start and stop exactly in line with the intervals but for me it feels close enough.

If you zoom in on the shorter intervals at the end of this workout you can see that I’m getting close, but not exactly matching the power numbers during the interval itself. This is nearly as close as I get when I switch to resistance mode anyway so the hassle of switching modes doesn’t pay off for me.

Others (including the guys at TrainerRoad) swear by swapping modes and hitting things more precisely - I just find that when I swap I end up about as accurate as I get staying in erg mode but with more frustration about switching and whatnot


#3

I use the Core as well and I believe you can adjust for how fast your trainer transitions into the new power level under devices and then click on the settings of the Core (I am on Mac though and use ANT+ dongle).

I previously had it on 5 sec and now on 3 secs, but I think I will lower it just to see how that plays out.


#4

I’ve got the Neo as well and struggled with these short intervals in erg mode (less than 10 seconds) as by the time I’ve reached the wattage the interval is over. Perhaps I’m not attacking it enough but whatever I do can’t get the power matching quick enough. This then means I’m down on the prescribed power for that interval.

I’m sort of just accepting that’s how it is, as much prefer erg mode for the rest of sessions where I let the train tell me how hard to work and don’t have to think about it.

Also noted the power changes about 2 second before the interval starts or stops but I’m just used to that now and live with it.


#5

Do you mean power smoothing? If so, it doesn’t actually affect on the trainers responsiveness, it only smoothens the power graph that TR shows to you.


#6

For intervals >20 seconds I actually prefer the 5 second ramp time - I’m very curious how you find it with even lower than 3 seconds. Even at 5 seconds it sometimes feels like I’m pedaling into a wall (playing tricks on the trainer by pre-increasing cadence, etc). Since the TR software starts bumping up the power ahead of the interval start/stops I typically feel things start to ramp up 1-3 seconds before the interval starts and similarly ramp down 1-3 seconds before the interval ends

As for folks using other trainers - I’ve seen a lot of complaints or griping about response time on trainers that doesn’t match my experience with either the Kickr Core or the original model Kickr. Obviously can’t tell without having spent time on the other brands but it does feel like the difference in response time is magnified for these shorter intervals. Of course, I could just not care as much about short intervals so perhaps the things I’m incredibly focused on and picky about just don’t overlap with those complaints


#7

My experience having done these intervals on a dumb trainer (equivalent to resistance mode?) and with a Hammer, is that I much prefer the erg mode. I may not totally hit the power target, but all these microburst intervals have workout text about maintaining cadence between bursts (well all the ones I did), which I could never manage when having to change gear on the dumb turbo.


#8

I’ll have to double check when I get back on the trainer again to confirm that.
I do have the feeling that it did change the response time as well.

It seemed to have change to the situation trphntr describes, the Core did seem to follow it from 5 to 3 seconds.

I don’t experience the wall feeling though, but that might be that I haven’t trained on an FTP level that will trigger that, as I have just started training on the Core 2.5 weeks ago (actually started training in general on a smart trainer 2.5 weeks ago).


#9

I am fairly certain that it does not affect timing. All it changes is the display of the power values.

The timing is purely a function of any given trainer. All of them have some delay in changing resistance. To help offset that delay, TR sends the resistance adjustment command about 2 seconds before what we see in the blue blocks.

That is done to try and sync the resistance of the trainer with the timing of the resistance profile on screen.


#10

Just a note on this and the neo. I have 3-second power smoothing on TR but instant on zwift. When I do a TR workout with zwift on in the background, zwift shows that the ramp up to the interval wattage is basically instantaneous; TR just doesn’t reflect it because of the power smoothing. A review of my workouts generally confirms what I’m seeing, too. All that is to say, if you’re concerned you can’t hit the wattage for short intervals, try it without power smoothing to see quickly your watts are ramping up.


#11

I don’t have a ton to add here, just that whether or not Erg mode is successful for these short (< 30-second) high-power intervals, it really depends on the trainer. Some trainers are faster than others on how quickly they react.

In my experience with the Kickr (2017 and 18) and Drivo II, the Kickr is significantly faster at resistance changes. I have a whole other thread going on the slow resistance change speed of the Drivo II. IMHO, it’s unusable for intervals of under 30-seconds, as it will take 12+ seconds to ramp up the power. Ironically, it’s faster if the power difference is higher; going from 100w - 200w is slower than going from 100w to 350w. The Kickr on the other hand, can go from 100w to 350w in about 1 second, if you lead into it with proper cadence.

That said, even with the Kickr, doing workouts like Spanish Needle with 15-second on/off interval, it can be difficult. The Kickr would take 2–4 seconds to level out, but it wouldn’t always release the resistance as quickly… so my “on” intervals would be slightly longer than my rest interval… which made the workout harder than intended.


#12

Thanks for all the feedback.
Hmm I guess its going to be a case of trial and error and seeing what works best for me. I’ll report back here once I’ve done a few of the workouts with the microbursts in.


#13

You might find that for shorter burst type workouts, it might be worth switching to the big ring throughout, so that your trainer doesn’t have to work as hard to ramp itself to the desired wattage. Might mean slower cadence in the rest periods but I’ve found I can hit higher burst powers this way


#14

I actually think the general consensus is the opposite of what you’re recommending. Some (not sure if all) smart trainers definitely ramp up power faster, and maintain that power smoother, using the small chainring and a large-ish rear cog. This helps to keep the flywheel speed down, which actually helps the trainer apply resistance more precisely. I admit to not knowing the physics behind why that is so, but it is recommended by lots of people, and I can personally confirm it. I believe that TrainerRoad has in-app recommendations to this effect, and I’ve read it from their support staff as well.

On a side note, the small chainring/large cog effect that keeps the flywheel slower also helps with noise on some trainers (older Kickrs, for example), and helps to lower the “resistance floor” of the trainer… the lowest point at which it can maintain consistent resistance. I haven’t personally experienced this, but it is out there for certain trainers, in certain situations.

The only aspect where being in a larger chainring can “help” is that the higher flywheel inertia helps you to keep the pedals turning a tiny bit easier under high watt loads. I have found this benefit to not be worth the significant loss in power smoothness though (fluctuations +/- your target wattage are much higher in my experience). Maybe that’s just my OCD at wanting nice flat intervals though. :wink:


#15

The resistance floor can clearly be seen when doing the exercises on a handbike, as we have significanly lower wattage compared to the bikers. For ex. on the recovery phases, the needed wattage might be around 40-50W. That’s so low, that on Kickr Snap, I need to you for ex. 39T/25T on a 26 inch rim, so that the flywheel speed is low enough to keep the wattage stable, not fluctuating too much.

As an example, here is the power curve for Kickr Snap:
https://www.google.fi/search?q=wahoo+kickr+snap+2017+power+curve&rlz=1C1GGRV_enFI779FI779&source=lnms&tbm=isch&sa=X&ved=0ahUKEwifzfed65HeAhUGCCwKHbp1DdUQ_AUIDigB&biw=2560&bih=1298#imgrc=rSqvykoroBzp1M: