When I do anaerobic efforts in my 2018 kickr I have a really hard time getting my power to hit the target effort. This is especially the case with short efforts like 15 seconds.
I am using my garmin vector 3 power pedals (finally fixed!) with power match on. I have my cadence at 100 rpm and when the interval hits, my power jumps up well over the interval but invariably begins to drop below the target. Even when I try to spin up to 150rpm the power continues to drop and I end up with an avg lower than the target for that interval.
Is there anyway I can counter that issue or is that just how it is on erg mode with power match on?
Remember that when you change cadence in erg mode, the trainer will react with a power change. When you spin up fast, it will drop power fast.
Erg mode tries to keep the power on target, so when you jump above it initially, it will drop it. When you then increase your cadence, it will drop it more.
The other thing is that I find it both difficult and unrealistic to do these short efforts in erg mode. I’d much rather have to shift and change cadence for them. And I don’t really follow the power targets, I just hit it for a bit of load on the muscles.
True sprint efforts I have to do outside anyway.
Be careful when you do this. The power difference between the kickr and your power meter can be quite large. If you find your workouts a lot easier without the quarq or vice versa you should check the difference.
Mine was about 30 watts different (garmin vectors). I used to do it as well, now I always use power match on for power consistency after the kickr workouts were too easy.
If it’s an all-out Sprint effort (5 - 30 seconds), I switch off erg mode and use resistance mode. If it’s a block of these efforts, I’ll keep it in resistance mode because switching back and forth can be a pain!
My experience here is this requires practice. It should get better over time. What you need to try to get a feel for is the target power so you do not overshoot it quite so much. The tendency is to watch the power numbers climb and pedal harder and harder until they hit the target, but the reality is it’s an average so your power may already be there before the average gets there and you need to get a feel for what the power “feels” like. Then it’s a matter of keeping the cadence consistent. what you should shoot for is a nice plateau shape rather than a shape that has a big spike at the beginning.
I did Eisen yesterday - 10 x 2mins @ 107% FTP, with 4x6s sprints from 150-200% in each interval. Doing it in erg mode on a Tacx Flux S. As long as you set your gear and cadence before the interval starts (5 seconds is enough), and hold that cadence through the sprint, it works - you are +/- 10% of the target within a second or 2. I’m not sure if powermatch slows things out, I’d assume it slows the final 10%. But the key to using erg for short intervals is to keep cadence constant. The more you chase power by changing cadence, the longer it will take to stabilize.
This will likely vary from trainer to trainer, and maybe between users too. Some trainers respond to wattage changes faster and can meet most of the power target on point. Even the ones that don’t are still close when you look at the actual power graph and not just the defined interval summary.
I’ve covered that issue a couple of times. The summary looks like you missed it, but the couple second delay at the start also happens at the end. So you often get the same “time in zone” for the power, but it’s slightly delayed on the graph.
One trick I sometimes to is slow my cadence about 10-15 rpm from my planned target. I roll right up to the start of the interval at say 80 rpm, then jump on the cadence quickly up to 100-120 rpm (depending on the effort and length). That can give a faster jump in power and less overall resistance change from the resistance unit since it was already a bit more “tight” from the initial slow cadence.
A zoom in on one set from Eisen. I’d say it works… I ramp cadence to 105-ish before the start of each 6-seconds sprint, and ramp up from there towards 115-120 in each sprint. TR changes power demand approx 1s early, both up and down, so you see the green line (demand) a but ahead of the blue block, but you also see actual power (yellow) pretty much right on the button all the way to 200% FTP. There is more of an undershoot at the end of each sprint because I let the cadence drop in a couple of seconds.
As a (former) control systems engineer, I’d say that’s a nice tight control loop. Keep in mind that this part of the loop (demanded power to actual power delivered) sits in the trainer, not in TR. Conversely, the power match loop (changing power demand to close the gap between requested level and powermeter-measured actual) sits in TR, on top of the trainer loop.
Recent suggestion on here was to have the Kickr paired via Bluetooth, your vectors obviously will use ANT. The trainer was quoted as responding quicker in BT. I use Vectors and Kickr combo myself (usually Win10) and this generally works for me during these short efforts. The pic above is reflective of what I see
One extra point on this topic: the interval summary, be it live on screen or in the analysis after the ride, will generally be off (low) on such short intervals. If you look at the zoomed-up segment above, the power demand drops 1s before the end of the interval - it also goes up one second early. As the summary only measures the “real” interval, it will measure the early drop, but not the early rise. The intervals in the workout detailed above shows me off low by 2-3% on all sprints.
I need to try your way too. Like I said, I think this may well vary from trainer to trainer too.
I have visions of making an “ERG Tips & Tricks” video to capture stuff like this for easy reference of new ERG users. I will probably crowd-source for ideas like this too.
One more point - the power number displayed on screen (top left corner) is filtered - “smoothed” in TR terms - by averaging over the time period you select (Settings - Power Smoothing). I believe the default is 3 seconds. That by itself will give the impression that your trainer is taking more than 3 seconds to reach the target, even if it’s doing it instantly. In the sprints shown above, the power display barely reaches the target before the end of the interval, even though the recording shows a perfect match. Drop that power smoothing down if you want to see what’s really going on.
I’ve tried increasing the cadence beforehand and I think that helps, but I suspect it contributes to the trainer being confused about what resistance it should apply which leads to a spike, and then a big dip before you settle in. On short intervals, the interval may be close to over before you stablize.
My technique is to try to time the beginning of the trainer applying resistance. I know it generally happens 2 seconds before the start of the interval, so when I see the 3 seconds, I look down, breathe, and try to hit near the exact moment resistance increases and try to ride that up and up like a plane taking off the ground. The goal is to keep cadence the same despite the increase in resistance, where normally your cadence may drop for a second while you try to react.
Turning off erg is an option, but either way, it’s up to you to figure out how to hit the power. If you do it manually, you’re still going to be searching for it. I think erg still simplifies it even on the short intervals. I might suspect the speed of your trainer may make a difference in choosing this option or sticking with erg. I have a Neo, so I don’t have any problem with the responsiveness of the trainer.
