Drive length in ErgData

[jerg]

Does anyone watch this when rowing? I noticed that if I think "legs, hips, arms", I get a longer drive length. Just having to run those words through my head makes me wait on the arm pull longer (feels like forever since my instinct is to tense the arms and start pulling right away).

Anyway, drive length seems like an interesting metric for realtime feedback on sequencing in addition to the force curve.

[jackarabit]

Indeed I do. We are the same hgt. but I can't think the numbers would be the same as I have very short legs. FWIW, I see 97cm warming up and soon after 103-105cm. Today at just under 25spm and 150watts for threshold intervals, I was seeing 109-112cm. I am capable of 115cm if I pull the handle into the sternum with authority but seldom see 2 consecutive. Laughable to those lucky enuf to be born with the tall gene!

It is worthwhile ime to think "out loud" about the contributors to stroke length which we can control and improve: reach at catch, speed of leg push, layback and arms finish.

[jerg]

Thanks for the feedback. When I'm not paying attention to delaying the arms, I'll drop into the low 90s on drive length. When I am paying attention, it's usually in the 110-120 range.

You were absolutely correct about my bringing in arms too early on the drive. Now that I'm looking at the drive length, I'm waiting . . . waiting . . . still waiting and then pulling with the arms. As a result, that jerking of the chain that you noticed in my earlier video is gone.

I'll have to get another video up in another week or two.

[derico]

Funnily enough I tried the ErgData app for the first time 2 days ago and noticed Drive Length as the main thing different from PM5 display - so it gave me something else to tinker with as I rowed along in the 1.48 - 1.54 range at < 15 SPM.

[KenS]

This is just the thread I've been hoping for. Yes, since I downloaded the ErgData app, I've been almost obsessed with drive length. I am 6' tall (182.88 cm) and my drive length varies between 1.24 when I'm getting tired to 1.39 when I think about letting the arms just "hang" when I start the drive and then pull to the sternum.

I'm not sure going for the longest pull gets me my most efficient stroke, though. I feel like I'm faster with less effort when my drive length is between 1.27 and 1.33.

Anyway, that's what I've been trying to suss out from drive length - efficiency.

Thanks for raising the topic!

[jackarabit]

What of the remaining four parameters not available from PM (ED and PM have drag factor in common.)? Drive time, peak force, average force, stroke count? Useful?

I find stroke count useful in determining average stroke rate accurate to one decimal place by dividing stroke count by duration of piece in decimal minutes. Note that ED does no calc operation here but simply repeats the typically misleading PM result. I wonder why this simple calculation was not added to the ED app?

[jackarabit]

Omitted drive speed. Mildly interesting? Useful?

[at1839]

What of the remaining four parameters not available from PM (ED and PM have drag factor in common.)? Drive time, peak force, average force, stroke count? Useful?

@drive time, useful YES, I'm always under .70 and ut2 and usually under .60 for UT1 & up. This tell you the truth about SPM on *vertically impaired* people because at 20 SPM the recovery phase is already 3/1 for .7 drive time. Figure out what would happen at 30r20 with a drive time of .55

@peak force, unsure.

@average force & stroke count no need for ErgData of course.

@drive speed, unsure, re lenght/time .. who care?

@drive length I look at and I like it very much. Surprisingly at 5'5" my drive length is usually over 1.10 overall and peak easily to 1.20. Btw I must confirm

I'm not sure going for the longest pull gets me my most efficient stroke, though. I feel like I'm faster with less effort when my drive length is between ...

while my sweet spot looks like mostly 1.10



Cu. Paolo

[jackarabit]

Paolo writes:

@ drive time, useful YES, I'm always under .70 and ut2 and usually under .60 for UT1 & up. This tell you the truth about SPM on *vertically impaired* people because at 20 SPM the recovery phase is already 3/1 for .7 drive time. Figure out what would happen at 30r20 with a drive time of .55

I tried to figure out what would happen at 30r20 with a drive time of .55" I think you are proposing that a reduction of absolute (vs. relative) recovery time occurs by comparison to the example 1:3 ratio for .7" drive time? Or perhaps whatever happens presents either an opportunity or a difficulty for undersize rowers? Too deep for me!

I have observed in my "vertically impaired" ergng that very low rates (16-18) make even 1:2 drive to recovery ratio difficult to produce because the recovery portion feels unnaturally slow--to the degree that a pause is required at finish. I always assumed that this difficulty of stroke execution was specific to folks typically producing relatively short drive length.

@average force & stroke count no need for ErgData of course.

The PM force curve graph fills the bill for average force, yes. As I stated earlier, I find stroke count indispensable for accurate determination of stroke rate average as the PM calculation is notoriously inaccurate. ED stroke count/elapsed time in decimal minutes will get you stroke rate accurate to one decimal place. I've been doing this calc on all my daily training rows.

[TimDoyle]

You might find this useful

http://analytics.rowsandall.com/2017/06 ... box-plots/

[jackarabit]

Re: box and whisker plots, there are tutorials on the net for those of us unfamiliar with this graphic representation of statistcal trends. I burnt several of my remaining brain cells over these this morning. Looks like a bell curve distribution by another name. Apparently the amplitude of the "whiskers" or extremes is of very little significance but the amplitude of the box as well as its degree of vertical extent is very important in signifying trending stroke length and "tightness" of distribution of stroke lengths around a central mean value or node. So the value on the y axis of the box as well its degree of vertical compaction of values falling between 1st and 3rd quartile is supposed to tell us the likelihood that higher or lower values are being produced with a frequency which indicates a greater or lesser degree of habituation to a more or less productive stroke length. In other words, are we improving on this performance parameter and if so, are we doing so consistently?