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PM5 average stroke rate - what's occurring?
Posted: August 20th, 2024, 9:24 am
by hikeplusrow
Did 10k on the RowErg this morning with an average SR of 19. However, only one of the 2k splits was at 19, the other four were 20/21. How could the average be 19? (Not the first time I've noticed this phenomenon.)
Re: PM5 average stroke rate - what's occurring?
Posted: August 20th, 2024, 9:31 am
by JaapvanE
One of the key things to remember here is that it is a rounded number. So those 19SPM's might actually be a 18.5, where those 4 20 SPM's might actually be a 19.5. Combined, the'll give a 19 SPM.
In all honesty, there is a lot of weird rounding going on. I frequently see a time on my PM5, and then get a 0.1sec difference with ErgData and the logbook.
Re: PM5 average stroke rate - what's occurring?
Posted: August 20th, 2024, 9:42 am
by Dangerscouse
I've seen really strange roundings, even when the total stroke rate will confirm a specific spm, so it can't be a rounding error.
I've given up trying to understand it as it's not that important, and it will only give me stress
Re: PM5 average stroke rate - what's occurring?
Posted: August 20th, 2024, 10:10 am
by Citroen
The problem is that Concept2 got some of their maths wrong with the first of the electronic performance monitors, they still round down for everything. Because they want to keep the numbers consistent (between a PM1 and a PM5 ‽) they have always stuck with rounding down (even when rounding up would make 1000 times more sense).
I've asked them in the past to re-consider how they round numbers, but no joy from that.
Re: PM5 average stroke rate - what's occurring?
Posted: August 20th, 2024, 10:16 am
by JaapvanE
Citroen wrote: ↑August 20th, 2024, 10:10 am
I've asked them in the past to re-consider how they round numbers, but no joy from that.
That explains a lot of weird deviations I see when comparing PM5 data to ORM for the same session (the joy of calibration...
).
Re: PM5 average stroke rate - what's occurring?
Posted: August 20th, 2024, 11:01 am
by iain
While some of the reports may suggest otherwise, I thought that the overall average was a rounded down average of the intervals. If the intervals are uneven this gives a wierd look. So a recent 5' done on "Just Row" showed rates of 28 and 0 in the intervals (stopped as crossed line), but this was averaged for the 5:05 at R14! Not sure whether "Just Row" is different and this is also effected in longer "Just Rows" as each 5' is recorded then combined. Haven't monitored those rounding to 20' intervals or longer, but say 4 10' intervals of 18 for first half and 17 for second then last at 17 for first half and 16 for second will round to 17,17,17,17,16 averaged to 16 despite (ignoring averaging in each 5') 865 strokes in 50' 17.3 actual.
Re: PM5 average stroke rate - what's occurring?
Posted: August 20th, 2024, 11:05 am
by iain
iain wrote: ↑August 20th, 2024, 11:01 am
While some of the reports may suggest otherwise, I thought that the overall average was a rounded down average of the intervals. If the intervals are uneven this gives a wierd look. So a recent 5' done on "Just Row" showed rates of 28 and 0 in the intervals (stopped as crossed line), but this was averaged for the 5:05 at R14! Not sure whether "Just Row" is different and this is also effected in longer "Just Rows" as each 5' is recorded then combined. Haven't monitored those rounding to 20' intervals or longer, but say 4 10' intervals of 18 for first half and 17 for second then last at 17 for first half and 16 for second will round to 17,17,17,17,16 averaged to 16 despite (ignoring averaging in each 5') 865 strokes in 50' 17.3 actual.
As it seems that generally people do restricted rate rows to count at whatever is recorded for the whole, many people do 21 5 times and 20 once for a 30R20 that is >R20.8. Don't know what the "rules" for setting the intervals are. If no rules then someone could set 29:59 intervals and could do R41 so long as they finished their last stroke before the beginning of the last second!
Re: PM5 average stroke rate - what's occurring?
Posted: August 20th, 2024, 2:41 pm
by hikeplusrow
Dangerscouse wrote: ↑August 20th, 2024, 9:42 am
I've seen really strange roundings, even when the total stroke rate will confirm a specific spm, so it can't be a rounding error.
I've given up trying to understand it as it's not that important, and it will only give me stress
I'm thinking that's probably the best approach
