ErgData Stroke Counter

[jurgwhitehouse]

I did a 30min rate-20 yesterday and wanted to nail 600 strokes exactly. Rather than count the strokes myself I outsourced the task to ErgData, and with a little fine-tuning during the piece, hitting 120 strokes every 6min split, I pulled the 600th stroke just before the 30 minutes were up. Pleased as Punch, or as pleased as I could be while still at max heart rate, I took a screenshot of ErgData:



Image my horror when I checked my entry on the Logbook to find this:



The downloaded CSV data confirms it was 599 strokes.



But it said 600 on ErgData! What's going on?

[Allan Olesen]

I guess this has to do with: When is a stroke counted as a stroke?
Is it at the end of the drive phase?
Or is it at the end of the recovery phase?

In the first case, your stroke no. 1 would only consist of the drive. Each subsequent stroke would consist of a recovery, followed by a drive.

In the second case, each stroke, including the first stroke, would consist of a drive, followed by a recovery. But then your recovery would be missing from the very last stroke, because the recovery ends when the next stroke's drive phase starts.

So no matter how the PM and ErgData counts your strokes, there will be some kind of problem at the end or beginning of your session, and some

I can see that your very first stroke took 2.9 seconds. My guess is that this was counted at the end of the recovery phase.

I wonder if Ergdata counts differently and counts each stroke at the end of the drive phase.

[Citroen]

The PM5 clock starts at the end of the first drive.

If you want the clock to start first

Main menu
More Options (button 5)
Racing (button 2)
Wait ...
Create Race (button 5)
Custom (button 5)
Time Race (button 2)
Dial in the time (usual way)
Button 5 (to save the race program)
Start Race (button 5)
Wait ... (configuring race)
Sit Ready (pick up the handle)
Attention (brace at front stops)
GO (and the clock starts before your first stroke)
When you're done [MENU] to save everything.

[jurgwhitehouse]

The PM5 clock starts at the end of the first drive.

A-ha, so it's all about how the first stroke is registered and nothing at all to do with the last stroke. And it depends on how the PM5 clock is started. I had to prove this with my own experiment...

I set up a workout of timed intervals and looked at how ErgData deals with the first stroke taken at the beginning of each interval. Interval number 1 is started by taking the first stroke; All subsequent intervals are started by the clock at the end of the rest period. I took a screenshot of ErgData at the end of each interval to get a tally of total strokes taken.

On the first stroke of the first interval, the timer starts at the end of the drive of the first stroke.

When is a stroke counted as a stroke? Is it at the end of the drive phase? Or is it at the end of the recovery phase?

By observing the counter on ErgData it appears to tick up at the end of the drive. I suppose it does it this way because the PM5 can only see frequency of 1s and 0s. It can't see the recovery phase of the stroke, so my guess is that it registers a stroke as done once it starts to detect a deceleration of the flywheel.

That first stroke, starting the clock, displayed on ErgData as 1, but it's not shown on the Logbook data. It's stroke zero. Stroke number 1 was actually the second stroke taken, 3.2 seconds later:




Stroke count for interval 1 was 451, but 450 were recorded for the Logbook.






I then started rowing again before the start of the 2nd interval. It's still in the rest period so ErgData ignored that first stroke and only started counting once the clock had started again. That makes sense because this work interval was started by the clock and not by the first stroke. This stroke number 1 on ErgData is recorded as 451 for the Logbook data:




442 strokes were taken during this interval. This time it matches with the Logbook:


(450+442=892)




Onto the 3rd interval. This time I waited for the clock to start before taking the first stroke. Again, ErgData recorded this a stroke number 1. The Logbook as stroke number 893.




445 strokes were taken, same as the Logbook.


(892+445=1337)




So, the only way to get ErgData stroke count equal to the count registered on the Logbook is to set up the workout as a race...

Main menu
More Options (button 5)
Racing (button 2)
Wait ...
Create Race (button 5)
Custom (button 5)
Time Race (button 2)
Dial in the time (usual way)
Button 5 (to save the race program)
Start Race (button 5)
Wait ... (configuring race)
Sit Ready (pick up the handle)
Attention (brace at front stops)
GO (and the clock starts before your first stroke)
When you're done [MENU] to save everything.

...so that clock starts before the first drive is completed. Otherwise, if it's a workout started as a normal workout, the actual number of strokes taken in total will be shown accurately on ErgData but will be one stroke fewer on the Logbook data.

Not that any of this really matters (unless you're pedantic)

[Citroen]

If you ever get to a public race (WIRC, BRIC) the clock starting first is how the venue racing works. Folks always complain after their first race that they lost some time because of that. My small program for the PM5 (works on PM4 as well) gives you a chance to practice your venue starts.

If you have more than one ergo (up to eight) you can run a full-on wireless race.

[jurgwhitehouse]

I did try this function on the PM4 when preparing for BRIC last year. A nice feature to get familiarized with a race start. It's certainly a different way of starting than we're used to. When you see ROW the clock has started ticking!

With an initial reaction delay, it becomes quite noticeable how much it affects your average pace in the first minute of a 2K race, and quite demoralizing if you didn't pay enough attention at the start.

[Allan Olesen]

It can't see the recovery phase of the stroke,

Yes, that was my point. It can only see the start of the next drive phase, coming after the recovery.