Where do the numbers on the Activity page come from?

I have a iPad that I use to direct a training activity. During the activity there are 6 numbers on the screen, top to bottom, left to right, power, target power, remaining time in interval, total time in activity, heart rate and cadence.

My smart trainer (with a power meter), my pedals (power meter and cadence) and my cadence sensor are all paired with the iPad. So, my question is, where power and cadence numbers coming from? Which device supplies what?
A corollary: does anyone have details on how ERG mode works? What power number is, actually, being sent to the trainer, so that it can adjust its resistance? Is it, perhaps, the average of the last 3 seconds of readings from the pedals?
Cheers,
-blake

Click on devices when in a workout, it will show you which ones are being used.

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When I click on “devices” it shows me the devices that are connected, not the ones being used.

I see that there is a partial answer to this quesion here: Smart trainer power meter Cadence question. Apparently the app has a hierarchy of devices and chooses the “best” device based on that hierarchy. That is very cool.

I still wonder how ERG mode works.

I have Garmin Power meter pedals and Kickr Core. I have configured the Kickr Core to broadcast the Power meter wattage which Zwift or TR uses to control the trainer (as I understood). Can’t you do that? Then you always know.

Pretty much :+1: Explaination in the blog


Hey! Let’s break this down to make sure everything is clear regarding where the numbers on the activity screen come from and how ERG mode works. The information below assumes that you have a stable and reliable connection to your devices.

Cadence:

When you have multiple devices, TrainerRoad prioritises the cadence reading from devices in the following order; cadence sensor, speed/cadence sensor, power meters, trainers.

Power:

If you have a power meter paired and it has a consistently strong connection, TrainerRoad will prioritise power from your power meter.

If you also have a smart trainer, you can enable PowerMatch in TrainerRoad’s device settings. PowerMatch allows you to get reliable and consistent power readings from your power meter (both indoors and outdoors) while still using erg mode on your smart trainer.

In ERG mode, your smart trainer adjusts resistance to match the target power set by your workout.

Here’s how erg mode works:

TrainerRoad sends the target power from the workout to your smart trainer.
The trainer compares this target power with the real-time power data from your power meter (if you have one) or your trainer’s internal power meter, and continuously adjusts resistance to keep you at the target power.

The trainer dynamically adjusts resistance to keep your power as close to the target as possible.
If your cadence decreases, the trainer will increase resistance to maintain the target power. If your cadence increases, resistance decreases accordingly.

Power Smoothing:

Instantaneous power can appear very ‘jumpy’, which makes it difficult to gauge how much you actually need to increase or decrease your power to hit the target power.

We’ve enabled Power Smoothing to make sure you don’t get distracted by seemingly “jumpy” power readings. This helps the trainer avoid overreacting to momentary spikes or dips in power.
You can control your Power Smoothing settings from the Settings section of the app. You can learn more here!

Cadence in Erg Mode:

Cadence is critical in ERG mode, as sudden changes in cadence can momentarily affect the trainer’s ability to stabilise resistance. Aim for smooth cadence to optimise the ERG experience.

I hope this clears things up! Let us know if you have any other questions! :blush:

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Brilliant, @SarahLaverty! Thank you!

One more thing


Your description suggests the my Trainer (a Wahoo Kickr Snap, in my case) somehow has to know about my power meter pedals? Is that so?

If it is just using it’s internal power meter, that would explain some of the discrepancy I’m seeing


Thanks a million
-blake

You’re so welcome! :smiling_face:

TrainerRoad knows what devices are connected. So TrainerRoad knows you are pairing power meter pedals and your trainer. Assuming they both have a stable connection to TrainerRoad, we’ll display the readings from one device if multiple devices measure the same metric. We typically prioritise the device that is generally considered more accurate for that particualr metric. For example, power meter > smart trainer (for measuring power).

Does that answer your first question?

Where are you seeing the discrepancy?

Let me know–I’d love to help clear things up for you! It can be a lot to navigate when you’re getting started!

Hey @SarahLaverty , I think I am almost there. You said:

The trainer compares this target power with the real-time power data from your power meter

How does the trainer get data from my power meter (pedals)? Is the trainer road app forwarding it, somehow?

My hypothesis, at this point is that my trainer has no idea what my power meter is saying and is adjusting its resistance based on its own, internal power readings.

This would explain why, I seem to have to accelerate/push harder to read a steady power output

Suppose the target is 100W. My pedals report, e g. 100W so I see 100 in the app. The trainer, on the other hand, reads 110W. It decreases resistance, slightly to accommodate. Now my pedals ready 90W, so I accelerate to get back to 100. Lather, rinse, repeat.

-blake

As I understand it, when using the trainer power, ERG is closed loop within the trainer. TR sends a power to the trainer and the trainer does the rest, sensing power and adjusting resistance as needed to maintain it. If a separate PM is used, then TR reads the power and sends commands to the trainer to adjust resistance up/down until the separate power meter reads the correct power. This is more roundabout, and in my experience doesn’t control power as quickly or tightly as using the trainer for power.

I believe Systm does something called “power match”. There, it sends a power to the trainer and the trainer maintains it. Systm then compares what it’s getting from the the separate PM and applies a correction to the power it’s sending to the trainer. This is done slowly such that it’s the trainer that controls for rapid changes in commanded power and fluctuations in cadence.

IDK if TR has implemented something like this.

TrainerRoad has PowerMatch enabled by default when you have both a power meter and trainer connected to TrainerRoad. I’ll link that information about PowerMatch again here.

Just to confirm, are you pairing both of the devices to the TrainerRoad app? If you are pairing either of the devices to another app, please disconnect them from other apps or devices. Bluetooth devices can only pair to one receiver at a time, so if they’re already paired somewhere else, it’ll interfere with the connection to TrainerRoad. That includes your phone, tablet or laptops’ internal Bluetooth. You’ll want to make sure your trainer and power meter are paired to the TrainerRoad app only.

Here are some other suggestions that should get to the bottom of this. We’ll want to make sure the connection between the TrainerRoad app and your devices is as strong as possible for the best experience in erg mode.

  1. Smooth pedaling: ERG mode works best with a consistent pedal stroke. If your cadence varies significantly, the trainer may struggle to adjust resistance smoothly.
  2. Stable connection: PowerMatch relies on a strong and stable connection to both your power meter and trainer. Here’s what I’d like you to do to strengthen the connection to your devices:
  • Make sure battery saving settings are turned off on your device.
  • Closeout of all other apps/programs that may be running in the background - This will make sure there are no apps that could be interfering with TrainerRoad. Additionally, we’ll want to make sure our devices are completely unpaired from any other fitness app.
  • Turn off all other wireless devices in the room including speakers, headphones, keyboards, computer mice, etc.
  • Let’s have you try uninstalling any other fitness app - We’ve found that certain fitness apps, such as Wahoo Fitness, can poach wireless connections and prevent devices from being able to stay connected in TrainerRoad. For that reason, let’s have you try uninstalling these apps for your next ride, even if it’s just temporary.

Give those steps a shot and let me know how you get on :slight_smile: .

Thanks, @SarahLaverty : You confirm, then, that TrainerRoad is sending both the target power and the power reading from the pedals (not just the target power), to the trainer. If that is the case, I will have to look elsewhere to find out what is going on.

As if i can turn off all other wireless devices in the room!! As if!!! LOL!

Reading the link you referenced (quote below), it says TR Power Match sends resistance to the trainer, not power, which would mean that TR remains in the loop controlling resistance vs rpm rather than leaving that to the trainer and simply adjusting the commanded power. IDK if the TRstatement is technically correct or not, but if it is, then that would slow response to commanded changes and rpm such that regulation wouldn’t be as good.

“
PowerMatch will use the power readings from your power meter to control your smart trainer. TrainerRoad will measure the power offset between your power meter and smart trainer; it will then adjust the resistance of your smart trainer
”

Hey!

I want to make sure I understand the issue you are facing. We’ll circle back to the thread once we have figured this out so that other people can learn :slight_smile: .

Just a couple of questions:

  • on which device/app are your reading the power from your power meter?
  • on which device/app are you reading the power from your trainer?

TrainerRoad is sending an offset value to the trainer. TrainerRoad will measure the power offset between your power meter and smart trainer; it will then adjust the resistance of your smart trainer based on that offset in power and the current interval target.

Cheers, Sarah

Hiya Sarah,

Thank you SO much for reaching out.

I think I mentioned in my OP that I running TrainerRoad on an iPad. When I do a workout, paired with the iPad are:

  • the trainer, a Wahoo Kicker
  • Garmin heart, cadence and speed sensors
  • Look power-meter pedals.

I’ve set the the trainer in ERG mode.

The only place that I am reading power is on the iPad, using the TR app. Actually I think that on the devices page, I could see what the pedals were reporting and what the trainer was reporting, separately. I’ve nearly never bothered to do that. I just see the power reading that the TR app shows during an activity. My original question, in fact. was about where that number came from. Did it come from my pedals or from the trainer? Was it an average over time?

But now you’ve already answered nearly all of my questions. The responsiveness of the TR team has just about spoiled me for any other athletic service. You folks are just amazing.

Let’s just move past my original question, given your answers: it might just be confusing at this point. Let me say what I think is happening.

First, TR is showing, in the number in the upper left of the activity page, the most recent power reading from the pedals. It shows the target power as a number below that. It also shows both, again, graphically, with the average power calculated over a number of seconds settable elsewhere in the app, on a thermometer in between the two numbers.

It sounds like TR calculates the difference between the target power and the most recent reading for power that it receives from the pedals It calculates this difference using the most recent reading from the pedals and not, for instance, the average power over the last few seconds. It reports the calculated difference to the trainer and the trainer, in turn, adjusts its resistance.

I am mostly just curious about how it all works. 
 and, for the most part it does just work. I do have some issue with the way my setup, in particular, handles, especially sprints and some high power intervals. In 30 sec sprints, even if I keep my cadence within ± 1 rpm, the resistance often does not stabilize within the sprint interval. Similarly, during relatively long, high output intervals I find that I have to progressively increase my cadence to keep my power output on target.

Neither of these things are a significant problem. I just do increase my cadence. It works fine.

My current hypothesis is that my Look pedals are very slow to report power. I suspect, from using them with their own app, that the power they report is the power that was applied to them as much as 3 or 5 seconds ago. I suspect this lag causes oscillation that only stabilizes in long, lower effort intervals.

Again, thanks just a million for indulging my curiosity.

-blake