Burst intervals on Kickr Snap

trainer

#1

I’ve been dreading doing Spanish Needle for…basically forever, but it was on my calendar for today. I wasn’t sure how well it was going to work because I have a Kickr Snap, which has its own set of nuances that make fast changes difficult (it doesn’t respond immediately).

Just as I expected, Spanish Needle was basically impossible, but not really for the reasons I anticipated. The response time was much faster than I expected, but the biggest issue came during the recovery sections—since there’s a floor to how low the power can go with the Snap given a certain cadence and gearing, there’s no way I was getting down to 40% FTP. I feel like that 15 seconds of recovery is crucial to finishing this workout (I made it through two intervals before I had to call it quits), and the lowest I could get was more like 70% FTP. That’s a pretty big difference.

Curious to hear how others with a Snap (or any other wheel-on trainer) handle this type of workout because I have several workouts coming up with some type of microbursts involved. This will be my last season with the Snap as it were—it’s a great little trainer, but things like this make me realize it’s time to move on to a direct drive trainer.


#2

What wattage numbers are we talking about for the peaks and valleys?


#3

Usually on rides of that type I can do it by finding a suitable gear on the cassette and swapping between chain rings for the peak and valley.

I checked and I haven’t done that particular one but the principle should hold. You may also need to shift on the cassette too.

It also looks like a workout you might consider doing in slope/resistance mode rather than erg.


#4

I ride 1x, so I only have a 50t chainring. :confused:

Makes this particular situation even more challenging.


#5

300 watt peak, 80 watt valley. FTP is 200.


#6

So, for the valleys your target power was 80, but you were hitting 140 instead. I have a Kickr Snap too and the last time I did Spanish Needle, this was my ride file.

In the valleys the trainer was able to get down to 100 or so. This would likely have been in a 39x21 gearing. I see that you’re using 1X, so there may not be much you can do to adjust your wattage floor (assuming you’re running your easiest gears already 50x42 I would guess).

My wife has a similar issue to you at a larger scale. Her FTP is 120, so due to the wattage floor, all her rides are basically the same. She’s yet to find out what a recovery valley is! :smile:


#7

My recommendation is to turn off ERG mode for anything less than 30 secs as I find that my Kickr snap takes about 15 seconds to adjust to a new power target in ERG mode, although this may just be my setup.

Right now, I have my Kickr snap controlled by my stages power meter in the Wahoo app and I have power match disabled in the TrainerRoad app. But, with this setup, it takes about 15 seconds for the system to adjust to a new power target with too much resistance during this time. I am going to try flipping it with power match enabled in TrainerRoad and disabled in the Wahoo app.


#8

I have the same setup, Stages in Powermatch with Kickr Snap, you can see my Spanish Needle ride file above. I get wattage adjustments much faster than 15 secs. What gearing are you running? You may be able to mitigate a lot of the lag from high wattage differential by lowering your inertia on the trainer.


#9

Yes. Very challenging.

All I can say is very fast gear shifts up several gears and do the workout in slope/resistance mode.


#10

@brenph I don’t see that making a difference. In ERG mode, the trainer knows that 140 is being dealt out and it’s trying to get down to 80, so it’s letting off all the resistance it can. A wattage floor is the same for ERG or Resistance modes.


#11

@julianoliver - Good tip! I am running big chainring on front and middle cog on back. If I drop to lower chainring that should take away a lot of the inertia and should help with resistance changes.


#12

Yes, try small chain ring and high on the cassette and see how that changes things for you. Most people report that dishing out high wattage intervals feels more difficult, but the trainer is more responsive to wattage changes overall.

The other thing to do your best with is keeping a consistent cadence through the wattage change. In ERG mode the trainer is trying to constantly match the target power, and fluctuations in cadence is another variable the trainer has to overcome.


#13

My trainer wheel has an 11-28 cassette, and I generally run in the middle somewhere. I’ll try moving up the cassette the next time I have burst intervals and see how that works. Trying to find the right balance where I’m still ahead of the pedalstroke on the hard intervals but still in a low enough gear to hit the “recovery” valleys properly is difficult.

Also, tell your wife I send my condolences and that she’s a bigger badass that most of us—I can’t imagine some of these workouts without a good recovery section!


#14

Short burst intervals on the Kickr Snap followed by deep short recovery valleys can be done in ERG mode just fine as long as you select a low gear (say 39-16), as the reduction in flywheel speed and therefore inertia is considerable.

Conversely, staying in a high gear means that the trainer, in the valleys, cannot produce a sufficiently low wattage resistance due to the high speed of the rear wheel and flywheel.


#15

That depends a lot on the needed wattage. If the wattage is low, as in my case, being a handbiker (FTP currently @ 112W), you may need to use a lot smaller gear, f.ex. 39-25 or even smaller, to get from low wattage to high and back to low quick enough.


#16

Wow, big respect for that wattage with a handbike! Your explanation makes sense, I must admit I didn’t appreciate that some of our TR members use their arms to turn the cranks.


#17

I’m on a KICKR snap definitely find similar issues to those described in terms of a lag to respond. I’m thinking of upgrading to direct drive kickr. Do those have upgraded find significant improvements?


#18

For workouts like Spanish Needle, I’ve always been curious as to whether or not these “sprints” are all out efforts or more closely connected to something like a 1st lap prem or something of that nature? It seems incredibly difficult to go all out on each one of these “needles”

Any feedback or thoughts from the forum or TR team would be greatly appreciated. I also assume these workouts should be done in the big ring while on my Tacx Neo.


#19

An ‘all out’ sprint needs ~12 min of recovery. These sprints are just shoving you up into z6, over and over again and forcing your body to cope with the repeated stress. You want to be able to get through all the intervals with good form on each set, not blow yourself up in the first set.


#20

Thanks for the note and feedback @ErickVH