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Nov 2017
2:17pm, 6 Nov 2017
3,256 posts
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larkim
@J2R - just taken a second look at my HR graphs to see whether there is any correlation between cadence & HR when the data goes screwy. I must admit I'd never really made that connection for the chest straps but had seen that with the optical wrist measurements.
Despite what I said, there is *some* correlation with mine, though it drifts in and out (hence me not drawing that conclusion before) and doesn't match 100%. e.g. first 1.5 miles of a run on Saturday
0.1 52 8:40 81 (81) 702 90 (92) No cadence match
0.2 48 8:00 88 (97) 681 92 (93) No cadence match
0.3 47 7:50 100 (118) 774 92 (93) No cadence match
0.4 47 7:50 175 (185) 1401 93 (95) Not quite cadence match
0.5 48 8:00 186 (186) 1488 94 (95) Close match (94 x 2 = 188)
0.6 44 7:20 182 (186) 1336 94 (95) Close match (94 x 2 = 188)
0.7 49 8:10 182 (182) 1485 94 (95) Close match (94 x 2 = 188)
0.8 49 8:10 181 (182) 1476 94 (95) Close match (94 x 2 = 188)
0.9 44 7:20 180 (180) 1320 94 (95) Close match (94 x 2 = 188)
1 42 7:00 182 (187) 1267 95 (95) Close match (95 x 2 = 190)
1.1 52 8:40 187 (187) 1621 95 (96) Close match (95 x 2 = 190)
1.2 45 7:30 178 (187) 1337 95 (96) Close match (95 x 2 = 190)
1.3 40 6:40 156 (175) 1067 95 (96) No cadence match
1.4 48 8:00 145 (148) 1158 96 (97) HR settled down
1.5 46 7:40 146 (149) 1120 96 (97) HR settled down
So fundamentally I've changed my tune here - there is some relation I think between cadence and HR in that period when the data is a bit dodgy.
But also, it's not that consistent - see for example this log where it drifts in and out all over the place, and even in the first mile the multiples still don't work - perhaps it started measuring cadence just on one side??
0.1 54 9:00 133 (178) 1275 87 (89)
0.2 49 8:10 175 (177) 1426 90 (91)
0.3 48 8:00 173 (173) 1384 90 (91)
0.4 51 8:30 172 (173) 1459 90 (92)
0.5 44 7:20 169 (169) 1239 92 (93)
0.6 44 7:20 169 (169) 1239 92 (92)
0.7 45 7:30 164 (169) 1236 93 (93)
0.8 44 7:20 126 (160) 975 93 (96)
0.9 41 6:50 99 (99) 677 93 (94)
1 41 6:50 99 (99) 677 93 (94)
1.1 48 8:00 99 (99) 792 94 (94)
1.2 43 7:10 98 (99) 706 93 (94)
1.3 49 8:10 95 (95) 776 94 (94)
1.4 42 7:00 95 (95) 662 94 (95)
1.5 48 8:00 94 (95) 754 93 (94)
1.6 48 8:00 95 (95) 760 94 (95)
1.7 42 7:00 97 (97) 677 94 (94)
1.8 49 8:10 97 (97) 792 94 (94)
1.9 42 7:00 97 (97) 679 94 (94)
2 45 7:30 109 (124) 782 94 (95)
Anyway, enough utterly meaningless drivel data...
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Nov 2017
2:57pm, 6 Nov 2017
6,305 posts
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paul the builder
Larkim - glad you've managed to use your data to confirm what other people have been telling you already 
I wouldn't expect it to be perfectly correlated, since there's competing patchy signal going on simultaneously (HR, plus some kind of electrical signal generated by the movement of man-made fabric over the HRM).
When I'm seeing it - I can make the number change both up and down from the 165-170 it generally reads (slower legs than yours ;-)) by changing cadence, or 'block' it by holding my hand on my shirt front to stop any fabric movement. And I also find it a *much* worse problem if I wear 2 layers of (loose) tech tops - which also tells me the fabric 'rubbing' and generating a tiny electrical signal is the issue.
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Nov 2017
3:01pm, 6 Nov 2017
5,045 posts
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chunkywizard
What HRM have you guys got? I've got a HRM-Tri from Garmin and never see this. I'm just wondering if it's older models that have the issue?
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Nov 2017
3:06pm, 6 Nov 2017
1,900 posts
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StuHolmes
I see it with both the HRM1 and HRM3.
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Nov 2017
3:19pm, 6 Nov 2017
3,259 posts
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larkim
I’ve got a Wahoo Tickr RUN.
@PTB - lol! I knew it went screwy for mile 1, I don’t think I’d ever encountered anyone saying that cadence for chest straps was coming across as a proxy, though I sort of knew that t-shirt static was likely to blame!
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Nov 2017
3:29pm, 6 Nov 2017
823 posts
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J2R
@larkim, I've never used an optical sensor, so when I've seen this, it's always been from chest straps. As I said, though, it has completely disappeared for me as a problem since I started rinsing the strap under a tap before putting it on. Not always the most pleasant thing to do on cold winter days, but I remind myself that if I start getting soft about stuff like that, I can kiss PBs goodbye!
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Nov 2017
4:02pm, 6 Nov 2017
6,306 posts
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paul the builder
CW - I've seen it on all 3 of the HR chest straps I've used - first a Polar one, then the Garmin 'hard strap' (the plastic foot-long thing across your front, elastic on your back), and now a Garmin 'soft strap'. Wish I knew the product IDs, but I don't, sorry
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Nov 2017
4:22pm, 6 Nov 2017
825 posts
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J2R
FWIW, the strap I'm using is an Anself/Abody (branding seems to vary) one off Amazon. Very cheap - strap was £6.99.
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Nov 2017
4:50pm, 6 Nov 2017
17,292 posts
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flanker
I've got the HRM-Tri and a i know there a couple of tops that will always give dodgy readings. They are all technical race shirts, so I suggest that its down to the quality of the fabric as I expect the race shirts aren't the best fabrics money can buy!
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Nov 2017
4:56pm, 6 Nov 2017
3,260 posts
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larkim
I've done the rinse on my straps ever since I've had one - still get the glitch on about 50% of the runs.
I used to have a HRM which would glitch in the first mile and then still not settle down, so I'm just grateful for these issues only ever persisting for the first mile or so. Though I do wish there was some way of easily suppressing the data as it does make reviewing history of HR a little unscientific.
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