Garmin kJ's vs Interval kJ's

1

I was wondering why the number ij Kj’s in Intervals is less than shown in Garmin. I would have thought they should be the same. Today’s Ride Garmin 1470 kJ’s Intervals 1437Kj’s
Anyone?

2

Is the activity duration the same?

3

Moving time Garmin 4hr 31m 47s Intervals 4hr 31m 27s so 20 seconds less in Intervals but that should make it only 2W less. Garmin FTP: 191W Intervals 192W but I can’t see how the number of Kj’s would be affected by a difference in FTP.

4

Yeah, you’re right; no effect.

5

Possibly because Intervals does “power spike detection” which in my experience is wrong. So I turn it off in Intervals by setting to 999:

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6

That doesn’t make sense, it seems you compare different activities - can you tell the kJ for those? Because 190w x 4.5h = about 3100kJ.

7

Thanks but I altered it and reprocessed the file but it stayed at 1437kj.

8

The 191W & 192W refer to the FTP settings in intervals and Garmin.
I can only wish to do 190W for 4.5 hours

9

Okay, I guess I misunderstood that. :smiley:

When I think about it more carefully, Garmin probably uses accumulated power to calculate the work, and intervals use the recorded values in seconds. Maybe these discrepancies are due to these different calculations and rounding.
Though, these errors are pretty minor (in my opinion).

10

I know but I’m a little OCD about these things. You may be correct In that the Garmin fit file the kJ’s seem to be accumulated in Joules to 3 decimal places. Intervals may do it slightly differently

11
12

Thanks. That would appear to be the reason, but I don’t and probably never will understand why even after reading through that thread.

13

Sorta like that elementary school game “telephone” where you sit in a circle and whisper a phrase to the person next to you, and then they turn and do the same, over and over, and by the time it gets to the end the phrase is not the same. Just sorta. But not really.

Attempting to simplify it for you…

Power meter “talks” to your Garmin. Talking is done with a radio, either bluetooth or ANT+ and sometimes there are dropouts and no data is sent.

There is a difference between how Garmin handles dropouts, and how Intervals handles dropouts. And that explains the difference in kJ.

14

Excellent. Thanks. I got confused at the first mention of radios as that made no sense to me tbh. :smiley:

15

Unless of course you have a bike with a power meter that has a cable to connect to your Garmin… but that doesn’t exist AFAIK