Form Sprints in ERG mode


#1

I recently got a kickr2018. Before this, I had a Lemond Revolution. I was doing Petit today which includes some form sprints. I was in a 50x19 using ERG mode.

I dropped my cadence to around 85 just before the sprint (which is 10 seconds long). Then, hopped out of the saddle and wound up to about 170 rpm before sitting down and hammering out the rest of the sprint. Not sure where I lost my form but pedalling was a little bumpy (not smooth) from a certain cadence (max was 184 which not sure its 100% accurate but anyway, was pedalling fast).

After losing control of the sprint cadence wise, it took what seemed like an age for the fly wheel to slow down to give me back power at a reasonable cadence. I’m guessing that I should try using 34x21 or something instead of the big ring for form sprints now with ERG mode to combat this as this would generate less fly wheel speed?

Am also thinking that those two form sprints that I did were not successful in that it would be better to keep smooth control during the complete sprint but I guess the power requirement was so light once the speed went up in ERG mode that it just let me spin like a mad man. Will see what a lower gear yields.

Interested to hear some feedback in the meantime on how others have addressed this.


#2

184 cadence, holy cow. Those are some track numbers!

For context, I typically ride around 100 RPM and this increases to about 105-110 for VO2Max intervals. When doing form sprints in Pettit, I focus on what I can control (no bobbing around slamming my butt on the seat like a pogo) and I see numbers around 125-130. Sounds to me like you’re focussing on the highest possible cadence you can generate, and missing out the “form” part of form sprint.

Here’s my ride summary for comparison (from Kickr Snap sitting in 39x18 BTW):


#3

Your experience roughly matches mine with both a Kickr and Kickr Core in that there is a short spike in power as you spin up the fly wheel, then it maintains roughly the correct power as I spin my legs as fast as they’ll go (I peak right around the same number as you and feel fairly in control there for that duration) and then a 15-20 second delay with no resistance as the fly wheel spins down and the trainer is able to apply resistance again where I spin my legs at their normal cadence and wait for the trainer to catch up to me

I completely agree with @julianoliver and his point that you’re not focusing enough on control. Obviously a learning experience with the leg speed with low resistance, but you want to stay stable and smooth while being fast - so if that limit for you is 150 instead of 180 - stick with that until you can creep higher


#4

Any chance you looked at heart rate and not cadence … 184 cadence seems really quick, like get that on video quick.


#5

I can’t speak for his ride, but 184 is achievable. Here’s the last ride I did that included form sprints:


#6

184 is definitely achievable, this is the part that creates concern in terms of correctly performing the drill:


#7

Absolutely @julianoliver. Previously on the Lemond (which I mentioned), I’d have to drop the gear before the sprint and build up leg speed but never got to go that quick as I could feel resistance the whole sprint. I guess what surprised me about ERG mode was the fact that the speed I generated made the resistance seem to disappear letting me spin up far quicker than I’d ever been able to do before and hence land me firmly in territory cadence wise that I was not familiar with and have little control over.

In retrospect, I think it was the bigger gear that got me into this, thinking about inertia of the flywheel and how long it took to slow down. I completely agree (and alluded to it in my thread opener) that these were failed form sprints because of my failure to keep (perfect) form during them… Need more perfect practice.


#8

Kickr 2017 and I stay seated and wind it up from low 90s to 130s to 140s while staying in control and good form. I’ve taken it 150+ but not in control.


#9

Yes, you can improve resistance recovery a bit by using a lower gear. It will keep flywheel speed lower and allow the break to grab a bit sooner-easier.

If you are on PC, I sometimes setup the Resistance mode with about 30% resistance.

In the easy part between the warmup and the first set,

  1. Press the ‘M’ key to quickly toggle control to Resistance mode.
  2. Use the right arrow or mouse to a Resistance to about 30%
  3. Press the ‘M’ key 2x to get back to ERG mode.

Now the trick,

  1. About 2-3 seconds before your Form Sprint, press ‘M’ and it will start to switch to Resistance.
  2. It takes a bit and won’t kick in hard until near the end of the 10 sec sprint. At that time, it hauls the flywheel speed down in a hurry.
  3. I switch back to ERG and back to the regular workout from there.

This can still work on mobile, but there is no fast shortcut to toggle modes. You have to go into devices, which kills the flow of the workout.


I need to make a Feature Request that reads a super high power and cadence (as in the FS) and then responds by applying direct braking for a few seconds before returning to the regular ERG mode.


#10

@tpodowd I’m guessing that if you can get up to those rpm that it would only be a matter of time before you could control it at that speed. With practice.

The issue with the KICKR is the flywheel carries a lot of inertia and the braking is set to get back to the Watts the erg is programmed for in that part of the workout so it is a bit of catch up since revs x resistance equals power and with such high revs the resistance becomes minimal.

I regularly am able to do 10-20 sec sprints at low watts and achieve over 200rpm (I have a sprint background). See below for a 206rpm session from within The workout Whorl. This is controlled, but then to slow down I either have to stay in contact with the rpms or just let the brake do it’s thing and slow down to a reasonable cadence again. This is just the nature of using a flywheel that is that heavy.

The other option is to do it as @mcneese.chad describes above.

If you can control them, these low power high cadence sprints can be a great tool

image


#11

@Lawrence is the Kickr your only source of power? I’m using PowerMatch with Stages PM and regularly see Stages report 300-500w at start and then settle down, but still about 60-80 watts higher than target as my cadence steadily climbs from 90s to 130s/140s. After shutting it down, I keep free pedaling at 60-90rpm and about 15 seconds later the Kickr catches up. Gearing is something like 50x18.


#12

@bbarrera the KICKR is my source for erg using an iPad with trainerroad (occasionally my laptop if I want to be able to quickly change modes as @mcneese.chad describes or for some workouts where I switch between modes) and I usually have my powertap p1 pedals also recording on my Elemnt bolt.

I have tried with it with power match and didn’t like how it adjusted as many have mentioned. My PTP1’s will invariably show a brief higher power reading but the average ends up being typically within 5watts or so with the pedals recording slightly higher but that is expected as they record almost instantaneous power fluctuations.


#13

@Lawrence this is from Saturday:

my best form sprint and unlike yours my peak power (at pedals) spiked for 1 second around 530W and then settled 60-80 watts above target. White line shows cadence slowly rising in a controlled way, ending at 150rpm. Surprised to see such low max watts on Whorl given you did a 10-20 sec sprint, at this point it doesn’t feel possible for me to do same without a large jump in power.

FWIW, I didn’t notice much of a difference when switching to power match on the Kickr 2017. Since its been 6 months or so, maybe its time to try disabling again and then knock out a form sprint or two.


#14

Cheers @Lawrence. Will certainly be trying to work my way up. I use an iPhone for TR these days though so can’t exactly follow @mcneese.chad awesome tips. Will be trying a lower gear though and report back.


#15

@bbarrera Do you have the latest firmware installed? It really shouldn’t jump that much if it’s in erg mode other than the initial part, which my power tap p1 pedals also show happens but then automatically settles in.


#16

yes, latest firmware for everything involved. I went back to Dec 2017 when starting SSB1 HV, as those were without power smoothing. However the Kickr defaults to power smoothing, so those workouts show nothing. I’ll do a couple of experiments and report back.


#17

Did a ramp test today, so had time to do a quick test after that to try some things. Good news is a 34x28 worked pretty well in terms of the flywheel not taking ages to catch up with slowing cadence after the sprint. I can still spin out so easily though but that’s ok. I think I have to stay seated for now and just work up the cadence. I started bobbing around 135 but was able to smooth that out so should be able to higher with some concentration and more practice. It’s a very different feeling to working up the cadence on the Lemond but I’ll get used to it. Lower gear is definitely a good thing for these to get the flywheel back fast.


#18

@tpodowd I’ve got the Kickr 2017 and long ago settled on something like 50x19 or 50x17 gearing. Today I had a long “Petit” like workout (Gibbs to be exact), and tried running 34x19 or 34x17 (not sure which) on the first 15 minute interval at 60% ftp. It was like riding on a slight decline, far too easy and nothing like a normal outdoor ride. Its hard to believe the 2017 Kickr is that much different than earlier or later models, so my question is did 34x28 feel natural?

BTW, the “catching up” part was basically the same for me on 50 ring vs 34 ring.

My conclusion today is the same as when I first bought the Kickr - the small ring is too easy and I doesn’t feel anything like riding outside.


#19

Hi @bbarrera - for the record, I did the ramp in 50x19 which is gonna be my default gear for any rides that I do. When I loaded the additional workout to test what I would do for form sprints, I basically just did a few sprints in 34x28 but didn’t do anything else worthwhile in that gear to know if it felt natural or not. I do think I read somewhere (in the manual?) that Wahoo recommend riding in a lower gear. I presume that is because it causes less wear on the system when applying whatever braking mechanism they use to require more power. I could be talking rubbish though :open_mouth:

Personally, I’m riding the bigger ring to log more speed and km (silly reason) as well as hoping that the inertia will help me from getting bogged down in harder workouts. I haven’t noticed that it feels better or worse in either ring itself, although it definitely doesn’t feel as good as the Lemond which I really enjoyed owning. To put it into something concrete, riding the Kickr always feels like you are on some kind of incline rather than trying to ride faster into the wind. Noisy though :headphones:!


#20

I use 34 and mid on fhe stock 11-26 cassette (not sure the exact size, but around 20t?) For all of my training. It sure doesn’t feel easy to me. The watts are there and lower inertia takes a serious toll on higher resistance or long & low resistance.

I used it that way all early season and nailed all of my events this season. So I am more than happy an will continue to use this range.

Maybe try something in the middle cassette and the 34t front, @bbarrera and see it that changes anything for you.