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beginner question - using 820 with a smart trainer

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  • beginner question - using 820 with a smart trainer

    I'm fairly new to cycling and have been spending far too much money indulging my interest of data and gadgets, but am uncertain as to the optimal way to record my indoor rides for future analysis. I am hoping some of you more experienced folks can give me some pointers.....

    Current Setup
    In the past couple months I've started using a Tacx Bushido trainer connected to Zwift. I think it's probably relevant to point out that I am doing this via Apple TV, which restricts bluetooth inputs to 2. The Taxc sends Zwift cadence and speed via one input channel (though I admit don't really understand how it measures cadence. Speed and power I can understand but cadence I can't fathom.

    I haven't been able to measure HR on this setup as the Tacx doesn't use ANT+, only bluetooth.

    Zwift uploads the ride to Garmin Connect which I use to log all my activities.

    I also have a FR645M that I've been using for outdoor rides up until now

    New Additions
    I now have an Edge 820 which I am setting up, but haven't yet used in anger.

    In addition I have fitted a Wahoo cadence sensor to the crank arm and a Wahoo speed sensor on the wheel hub. I've connected these to the 820.

    I've just now engaged a coach to help me get ready for my first Triathlon and she uses Training Peaks for the proscribed workouts and to evaluate performance afterwards.

    My Confusion
    So I now have multiple methods of recording an activity...... but I don't know if I should use one or the other, both, or if there is a way to have them work together. I'd like as much data as possible to be available to my coach

    If anyone can point a newbie in the right direction, I would be very grateful.

    Thank you

  • #2
    The trainer estimates cadence by detecting torque pulses as you pedal. This can be OK, but a dedicated cadence sensor is better.

    For structured training purposes, speed and distance are pretty much irrelevant. What matters is power (or RPE in the absence of power), heart rate, and cadence as functions of time. You want to use the best sources for these parameters. For power, a power meter on the bike is best, but using the trainer reported power is fine too. There are many heart rate sensors that work well...but optical watch type are usually the most problematic so a chest strap or optical arm band type are probably the best and most reliable. Crank or pedal based power meters can accurately determine cadence. Without one of those, a dedicated cadence sensor is best.

    You should ask your trainer what she thinks is best, but IMO for your situation, use the trainer for power, and your dedicated cadence and speed sensors for those. While riding your trainer, your training app will control the trainer and record your data, so in that app, you will need choose and link the appropriate sensors. For training rides outside, you'll be using RPE to gauge effort level and those same sensors to record the activity on your Garmin. Ultimately, whatever data is collected in your training sessions will be uploaded to your trainer's preferred app, likely Training Peaks in this case. Any activity your record on your Garmin and upload to GC, can also be uploaded to Training Peaks.

    Generally speaking, activity data files can be imported between apps, so you can record your activities in multiple places.
    Last edited by looigi; 01-14-2019, 11:08 AM.


    • #3
      Thank you looigi, that makes sense and is very helpful. Much appreciated


      • #4
        Hi, If you are conducting the trainings using zwift with the appleTV you use one of the twoBLTE channels available. The other one would be free for your HR monitor, and I don't understand what you mean by "I haven't been able to measure HR on this setup as the Tacx doesn't use ANT+, only bluetooth.". If you have a bluetooth HR monitor, everything will be recorded by zwift and then uploaded to Strava, Garmin connect, etc, for your coach to follow it. In addition, you can (if you want to) use your edge and FR devices to record power and speed/cadence through ANT+, simultaneously in both if you like. Although it is not clear fro your description, it seems that you do not have a HR monitor except the optic sensor of the FR645?. If this is the case, the only data stream containing all of the information for your coach is the FR one. IN those circunstantes you could certainly benefit from a "real" HR monitor, preferably a dual-band one such as the Wahoo tickr (chest) or the scosche rhythm (optical but accurate) which would allow you to record two parallell data streams (actually three) containing all of your sensor data (at the apple TV and at the EDGE/FR). The optical HR monitor of the FR is not good enough for accurate monitoring of the intervals so it is worth upgrading it anyway.


        • #5
          Originally posted by Baldo-Mero View Post
          I don't understand what you mean by "I haven't been able to measure HR on this setup as the Tacx doesn't use ANT+, only bluetooth."
          Thank you for the helpful reply, sorry I didn't spot it sooner.

          I made an error in the above. what I meant to say is that the only HR strap I have presently uses an ANT+ protocol only, therefore I have no way of sending HR to the Tacx.

          Anyway.....I've done a couple of trainer rides using the Garmin, which is working out well. I think I'm going to cancel my Zwift subscription. Zwift is good, but I'm not feeling like it's great value and I'm spending enough money each month right now on a gym membership and tri-coach......I'll likely re0instate it once I am done with the coach, and will certainly get a HR strap that uses BT also, per your suggestion.

          Thanks again


          • #6
            In my experience with trainers, they do not receive sensor data, like heart rate. You need the computer/app you're using to be able to receive the sensor data. It is usually possible to get an ANT+ dongle to enable a computer to receive ANT+ data. I haven't used Apple TV and don't know if this is possible. If you're successfully doing structured trainer workouts using your Garmin, there's really no need for Zwift, other than perhaps to make the workouts less tedious/boring.


            • #7
              I search information about smarttrainers. So, I read this post. Sorry to add my question here.
              If I make workout in GC with personalized power zone and I send it in my watch (920XT), watch can control trainer ?


              • #8
                No, the 920XT cannot control a trainer. For that you'd need a device with FE-C. Some more advanced biking computers can do that.
                Current: nuvi 255, eTrex 30, Forerunner 310XT, Forerunner 735XT, HRM-Tri, HRM-Swim, SDM4, Virb Elite, tempe
                Retired: eTrex Legend, Swim


                • #9
                  Thanks.Very usefull for next Garmin device.
                  I've got Elite Direto.