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RDPOD vs Hrmproplus

I compared the Vertical Oscillation, Ground Contact Time, Ground Contact Time Balance and Cadence data from the RDPod and the HRMproPlus Band. RDPOD data in red and band data in light blue. The balance is perfect with the RDpod averaging 50/50 while with the band it is 52.1/47.9. Ground contact time is 202ms with the headband and a bit higher with the RDpod. Note that from the meta the values are almost identical. Cadence is identical and vertical oscillation is also different with the lowest range and with the highest RDpod, values that both align as with the midstroke ground contact time. It should be noted that from the middle of the race, while the oscillation and ground contact time values align, the balance (around the 6th km) is misaligned, and by a lot. How do you explain such a difference between the ground contact time balance? Could it be that a change in the location of the Chest vs. Butt sensing makes such a difference?

0 Bitti over 1 year ago

I moved form Running Pod to HRM Pro+ a couple of months ago. When I compare my running reports in Garmin Connect, I see no change in ground contact time. The ground contact time changed a little for me (from sligth 0.5 %-point bias to the right to a similar bias to the left), and vertical oscillation dropped about 1 cm.

Of those changes, the vertical oscillation change is expected, since chest moves differently from waist. Even Garmin manuals list different values for RD Pod and chest strap for their color coding. For ground contact balance, I guess that's also explainable by the fact that our torso doesn't move 100 % symmetrically, causing a slight individual default bias. (And when you know it, you can ignore it and just concentrate on the value if it's different from before).

But I find it strange that your HRM Pro readings like ground contact time fluctuate so much more that RD Pod's. When I made the change, HRM Pro+ gives readings with less jumping up and down. Since those value are taken from accelerometer readings, was your HRM strap tight enough so that it wasn't bouncing up and down?

0 Piero over 1 year ago in reply to Bitti

yes my strap was on correctly. In my opinion, however, there is too much difference in the balance of the ground contact time