stroke rate reporting
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stroke rate reporting
probably been discussed before
does anyone know how the Stroke Rate as reported for a session is arrived at ?
I have observed that Heart Rate is simply a snap-shot approach: what the HR was at the end of the time period/s called for in the work-out's splits; and so a more "accurate" or finer grained assessment of HR can be had by requesting shorter splits within the overall session.
I've long thought / believed <?> that the watts (or calories, or time per 500 meters) were calculated on an "average" basis - but this may be an incorrect assumption.
My wish is that somehow the machine counts all the strokes in a given time period, and divides them to give a rather more accurately determined value than would be the case with the snapshot approach.
My current approach to rowing focuses a lot on lower stroke rates and limiting my effort to pre-determined "moderate" HR maximums - I'm an old guy just working to keep my heart and overall body in vaguely good condition, while refining the execution of a perfect technique - that is - for me, at present - rythymic and lovely and non-injurious. I aim loosely at 10 meters per stroke, so how the stroke rate is recorded is of obvious relevance.
does anyone know how the Stroke Rate as reported for a session is arrived at ?
I have observed that Heart Rate is simply a snap-shot approach: what the HR was at the end of the time period/s called for in the work-out's splits; and so a more "accurate" or finer grained assessment of HR can be had by requesting shorter splits within the overall session.
I've long thought / believed <?> that the watts (or calories, or time per 500 meters) were calculated on an "average" basis - but this may be an incorrect assumption.
My wish is that somehow the machine counts all the strokes in a given time period, and divides them to give a rather more accurately determined value than would be the case with the snapshot approach.
My current approach to rowing focuses a lot on lower stroke rates and limiting my effort to pre-determined "moderate" HR maximums - I'm an old guy just working to keep my heart and overall body in vaguely good condition, while refining the execution of a perfect technique - that is - for me, at present - rythymic and lovely and non-injurious. I aim loosely at 10 meters per stroke, so how the stroke rate is recorded is of obvious relevance.
Train Don't Strain ~ Think or Sink
The PM2, PM3 & Pm4 calculate watts are calculated on the basis of average speed (which is not the same as average watts!). This way you will always get the same watts fro the same average pace. The first PM reported average watts, although I am not sure of the exact algorithm. SO for the PM1 you would see different average watt numbers if you rowed the same distance in the same time, depending on how steady you rowed the piece.
I am almost 100% certain that the stroke rating counts strokes and divide by time.
I am almost 100% certain that the stroke rating counts strokes and divide by time.
- PaulS
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Just a guess, but I think the reported SR (being recalled) will be rounded number within the split. I've noticed that during my usuall S10PS sessions where the genuine SR is very near a 0.5 point between the displayed values I will get alternating whole values when the workout is recalled.
Of course there is the "Dart Game" which will give an idea of how accurately a SR is maintained, and when I was doing some testing of that for C2 I would generally get between 97-98% accuracy over 8k, I figure that must be reasonably accurate for SR consistency.
What I would like to see, would be 0.5 resolution for the displayed SR, it really is signifigant for those desiring to hold at a particular rate, especially if not adhering to fixed DPS (which takes care of itself).
Of course there is the "Dart Game" which will give an idea of how accurately a SR is maintained, and when I was doing some testing of that for C2 I would generally get between 97-98% accuracy over 8k, I figure that must be reasonably accurate for SR consistency.
What I would like to see, would be 0.5 resolution for the displayed SR, it really is signifigant for those desiring to hold at a particular rate, especially if not adhering to fixed DPS (which takes care of itself).
Erg on,
Paul Smith
www.ps-sport.net Your source for Useful Rowing Accessories and Training Assistance.
"If you don't want to know the answer, don't ask me the question."
Paul Smith
www.ps-sport.net Your source for Useful Rowing Accessories and Training Assistance.
"If you don't want to know the answer, don't ask me the question."
Less Sure
I am less sure than Paul, but have massively less experience.
On a previous thread it was said (and not disputed) that the SPM in an interval was the average of the displayed SPM during it. So if you row at 28.6SPM for 40% and 29.6 for the other 60% it would show 30 (rounded weighted avg of 40% 29 and 60% 30). Not 29.2 rounded to 29.
Further, the average SPM for the piece appears to be the average of the average for each interval (at least on the PM3's I use). On a "Just row" recovery, I averaged 21SPM for 5' and then stopped. The PM3 recorded a few seconds of a second interval as the flywheel slowed and showed 9 SPM for this short interval. The total showed 15SPM, even though this cannot have been below 20SPM on a true average. This is only important if different length intervals are used.
Paul has pointed out elsewhere that in rowing 10MPS, the best approach is to aim for the same units consistently at the catch. This makes the 10MPS accurate and so the stroke count is known accurately from the distance. The SPM can then be accurately calculated as time and no. of strokes are known.
I can confirm the PM3 does calculate Watts assuming a constant pace. I laboriously collected data for several weeks meaning to analyse how even I had rowed. The data all showed a constant pace!
Hope this helps
Iain
On a previous thread it was said (and not disputed) that the SPM in an interval was the average of the displayed SPM during it. So if you row at 28.6SPM for 40% and 29.6 for the other 60% it would show 30 (rounded weighted avg of 40% 29 and 60% 30). Not 29.2 rounded to 29.
Further, the average SPM for the piece appears to be the average of the average for each interval (at least on the PM3's I use). On a "Just row" recovery, I averaged 21SPM for 5' and then stopped. The PM3 recorded a few seconds of a second interval as the flywheel slowed and showed 9 SPM for this short interval. The total showed 15SPM, even though this cannot have been below 20SPM on a true average. This is only important if different length intervals are used.
Paul has pointed out elsewhere that in rowing 10MPS, the best approach is to aim for the same units consistently at the catch. This makes the 10MPS accurate and so the stroke count is known accurately from the distance. The SPM can then be accurately calculated as time and no. of strokes are known.
I can confirm the PM3 does calculate Watts assuming a constant pace. I laboriously collected data for several weeks meaning to analyse how even I had rowed. The data all showed a constant pace!
Hope this helps
Iain
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You can pretend that they are different arithmetical expressions of the same thing, because the performance monitor does. The PMs does not really reporting average watts as a physicist would define it. It is more like an "effective average watts". If you row with very uneven pacing it will be harder because it takes more energy and hence requires more watts.Sean Seamus wrote:goodness ! how can it be ? I completely thought they were different arithmetical expressions of the same thing.average speed (which is not the same as average watts
{{ PLEASE GOD, I hope this isn't one of those topics that only physicists comprehend . . . ! }}
This you should know from experience. However the performance monitor will always report the same "average watts" for the same pace.
But simply put, a Watt is a measure of Power which is proportional to the speed cubed.
Consider two numbers: 2 and 4. The average is 3. 3 cubed is 27.
Now take the average of 2 cubed and 4 cubed, that is 8 + 64, for an average of 31.
So the average of the a set of numbers cubed is not the same as the average of the cube of the same set.
They will be the same if the speed is constant, but if the speed varies it takes more power to go the same distance in the same time. This is the a major reason it is important to row a steady pace when racing.
Hope that is clear. If its not what can I say, I'm a physicist
If you can wade through it, the Physics of Ergometers is explained here:
http://www-atm.physics.ox.ac.uk/rowing/ ... meter.html
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Nosmo- Thank you - that is extremely clear - the focus largely on the meaning of "average", rather than on the equivalency of watts versus speed (all this in the context of the erg and the PM3)
that is to say - as I ( think I ! ) understand it - as reported by the PM3 : watts or time-per-500-meters are just arithmetic variants of the same somewhat flawed assessment of the effort applied to turning / accelerating the fan / wheel.
For a slob like me, the numbers express a consistent enough value to satisfy my simple requirements. Further, the "meters rowed" are derived from the same assessment model, and so to return to the original query -
allowing / accepting the number of imaginary meters rowed per block of time, how is the value for strokes per minute arrived at ?
What I'm trying to comprehend is, allowing for the . . . imperfections . . . in the measurements of imaginary distances, it is apparent to me that there is a real difference in . . . effort per stroke . . ., whether I pull 1,000 meters with 100 strokes or 200 strokes. If the reported strokes-per-minute are based on the model ( "snapshot" ) used for heartrate, then the value is, for my purposes at this time, virtually worthless.
The best, I think, would be a count, divided by time.
As an aside, I agree with Paul, that the addition of a decimal to the reported stroke rate is highly desirable, ( assuming - of course - that the reported value is accurate over the time being measured ).
Thank you very much for helping me with this.
that is to say - as I ( think I ! ) understand it - as reported by the PM3 : watts or time-per-500-meters are just arithmetic variants of the same somewhat flawed assessment of the effort applied to turning / accelerating the fan / wheel.
For a slob like me, the numbers express a consistent enough value to satisfy my simple requirements. Further, the "meters rowed" are derived from the same assessment model, and so to return to the original query -
allowing / accepting the number of imaginary meters rowed per block of time, how is the value for strokes per minute arrived at ?
What I'm trying to comprehend is, allowing for the . . . imperfections . . . in the measurements of imaginary distances, it is apparent to me that there is a real difference in . . . effort per stroke . . ., whether I pull 1,000 meters with 100 strokes or 200 strokes. If the reported strokes-per-minute are based on the model ( "snapshot" ) used for heartrate, then the value is, for my purposes at this time, virtually worthless.
The best, I think, would be a count, divided by time.
As an aside, I agree with Paul, that the addition of a decimal to the reported stroke rate is highly desirable, ( assuming - of course - that the reported value is accurate over the time being measured ).
Thank you very much for helping me with this.
Train Don't Strain ~ Think or Sink
I'm about to hop on the erg, and will do some stroke rating tests to confirm its behavior.Sean Seamus wrote:Nosmo- Thank you - that is extremely clear - the focus largely on the meaning of "average", rather than on the equivalency of watts versus speed (all this in the context of the erg and the PM3)
that is to say - as I ( think I ! ) understand it - as reported by the PM3 : watts or time-per-500-meters are just arithmetic variants of the same somewhat flawed assessment of the effort applied to turning / accelerating the fan / wheel.
For a slob like me, the numbers express a consistent enough value to satisfy my simple requirements. Further, the "meters rowed" are derived from the same assessment model, and so to return to the original query -
allowing / accepting the number of imaginary meters rowed per block of time, how is the value for strokes per minute arrived at ?
What I'm trying to comprehend is, allowing for the . . . imperfections . . . in the measurements of imaginary distances, it is apparent to me that there is a real difference in . . . effort per stroke . . ., whether I pull 1,000 meters with 100 strokes or 200 strokes. If the reported strokes-per-minute are based on the model ( "snapshot" ) used for heartrate, then the value is, for my purposes at this time, virtually worthless.
The best, I think, would be a count, divided by time.
As an aside, I agree with Paul, that the addition of a decimal to the reported stroke rate is highly desirable, ( assuming - of course - that the reported value is accurate over the time being measured ).
Thank you very much for helping me with this.
The equivalence of watts and pace makes sense from a practical point of view. It is an "effective average power" which is what counts in a race. Recording splits in detail gives you more useful information then a true average watts.
Similarly for heart rate--it makes sense to report it at the end of an interval.
C2 did really think about these things and did it intelligently.
How many strokes you take does make a diffference in how hard it is, but that is true of other sports too. If you spin at 75 RPM on a bicycle, it will feel very different from spinning at 150 RPM. Similarly if you run at a different step size it will make a difference. But within a limited range it will not matter too much.
SPM for an interval is the average strokes taken during that interval and not the terminal value (subject to averaging errors etc.). The terminal value is that shown on the screen when you stop rowing. You will need to go in to the memory to find the average.Sean Seamus wrote:...how is the value for strokes per minute arrived at ?
What I'm trying to comprehend is, allowing for the . . . imperfections . . . in the measurements of imaginary distances, it is apparent to me that there is a real difference in . . . effort per stroke . . ., whether I pull 1,000 meters with 100 strokes or 200 strokes. If the reported strokes-per-minute are based on the model ( "snapshot" ) used for heartrate, then the value is, for my purposes at this time, virtually worthless....
Regards
Iain
My experiments this morning confirm this. However for the average for the entire piece is the average of all the splits.iain wrote: SPM for an interval is the average strokes taken during that interval and not the terminal value (subject to averaging errors etc.). The terminal value is that shown on the screen when you stop rowing. You will need to go in to the memory to find the average.
Regards
Iain
This is a true average if all the splits are even, otherwise it is not. So if you set you monitor for say 11 minutes, and put the split at 2 min, you will get 6 splits--five at 2 minutes and 1 at 1 minute. Then if you row the first 5 at 20 spm, and the last one at 32, the average would be 22--(5*20+32)/6--rather then 21--(10*20+32)/11=21.09