A Newbie has some questions...

[lapresle]

Greg, Bob & Claus, thanks for the advice! I spent some time on the links (UK Interactive & Wolverine) and feel like I am starting to understand what people are talking about. I really appreciate the suggestions.

HJS, if I understand you correctly, what you're saying is that SPI is a measure of force applied during a stroke and not speed.

[jamesg]

"SPI", or Watts/Rating, is a measure of work - the actual work done during the stroke, = net length x average handle force. This is what an "ergometer" measures, by definition.

[Citroen]

"SPI", or Watts/Rating, is a measure of work - the actual work done during the stroke, = net length x average handle force. This is what an "ergometer" measures, by definition.

And what units do you measure SPI in? Does it have any units other than inverse square pico farads.

SPI is mostly meaningless. Ignore it or consign it to Room 101, it's not useful for improving your rowing.

[claus hansen]

...there are various ways of measuring ones progression.

I choose to measure my progression in terms of PB on various distances, Heart Rate over these distances - lower HR at same pace means better technique, endurance or more efficient combination of pace/strokes pr. minute. Also, I still believe SPI can be a valuable way of measuring progression too. For me it is valuable not only to better my PB on say 5000 meter but also do it with fewer strokes (higher SPI) maintaining the same technique, and preferably HR.

You do similar things in other sports, too. In svimtraining - freestyle - trainers advocate a 2:1 advantage of increasing strokelength (meters pr.stroke) over rate (strokes pr. minute). The addition of strokelenght (fx 40 strokes for 50 meters) and rate (fx 40 seconds for 50 meters) is called a 'golfscore'. This is widely used as a measure of progression. What is the unit of that?

Excuse my english in case I explain myself poorly...

[gooseflight]

"SPI", or Watts/Rating, is a measure of work - the actual work done during the stroke, = net length x average handle force. This is what an "ergometer" measures, by definition.

And what units do you measure SPI in? Does it have any units other than inverse square pico farads.

SPI is mostly meaningless. Ignore it or consign it to Room 101, it's not useful for improving your rowing.

Comparing SPI and the more meaningful and more widely used Distance Per Stroke (meters) is instructive The chart below shows values for a 1:45 split:

[NavigationHazard]

Umm, the standard unit for expressing WORK is the joule, which is defined as the work done by a force of one newton acting over a distance of one meter. The standard unit of POWER is the watt, defined as a work rate of one joule per second.

Dividing displayed watts by rating does NOT give you a measure of "actual work performed during the stroke." It gives you displayed watts (i.e. average output power) divided by rating. There's a reason that SPI as coined by Paul Smith stands for stroke power index.

One of the (many) reasons it's problematic as a stand-alone metric is that it's a fraction. Other things equal, high spi values are desirable. However you can raise SPI artificially: not by raising the watts but by lowering the rating. Suppose you produce 250w at 25 strokes/minute. That's an spi of 10. You can raise it to 11 either by rowing at 275 watts and 25 strokes/minute OR by rowing at 220 watts at 20 strokes/minute. The former is an accomplishment. The latter is simply gaming the numbers to make it look like you're doing something impressive. For SPI to have any useful significance in training it needs to be contextualized in terms of rating and also duration, such that you're comparing roughly similar pieces.

[claus hansen]

Very precisely expressed NavigationHazard. Exactly because of that I - being a newbie - find the 30r20 session very valuable, measuring progression in terms of both pace and HR and higher SPI (indirectly), without 'cheating'. I am now reaching a point, where I have difficulties improving my 30r20 pace whereas I can still better my 10 km. and 60 min. rows without going all out. This must be due to lack of ability to apply more force to the handle (HR going skyhigh in 30r20above SPI 8.8) whereas I can still higher the rate and/or force in longer rows. Hence I've found the concept of SPI helpful in order do analyse present situation and needs. I must - shamely - confess that I am far even from the 9.5 SPI considered a lightweight joke by Ranger, .

[hjs]

Greg, Bob & Claus, thanks for the advice! I spent some time on the links (UK Interactive & Wolverine) and feel like I am starting to understand what people are talking about. I really appreciate the suggestions.

HJS, if I understand you correctly, what you're saying is that SPI is a measure of force applied during a stroke and not speed.

Yes true, spi is simply watts divided by strokerate. Thas has only a meaning if you take time and rate together with it.
Every body can pull hard for a short while at low rates.

[lapresle]

I haven't taken the time to figure my SPI, I'm three weeks in and happy with time and meters. I like using the rankings to measure progress and in time, I would imagine I'll turn to other indicators to gauge my progress. For now, I'm enjoying the benefit of every day being a new PR.

[Carl Watts]

I haven't taken the time to figure my SPI, I'm three weeks in and happy with time and meters. I like using the rankings to measure progress and in time, I would imagine I'll turn to other indicators to gauge my progress. For now, I'm enjoying the benefit of every day being a new PR.

The Ranking system is great to see how your placed in your age/weight group.

Those that rave on about "how well they are now rowing" and "SPI...blah...blah" don't rank their results for some strange reason !

DPS is about the only thing of additional use that doesn't come up on the PM3 monitor and you know your making real progress when you get into double digits on your longer training rows.

[jamesg]

what units do you measure SPI in

The dimension of power (measured in Watts) is Work/Time. The dimension of rating is 1/Time.
So dividing Power in Watts by Rating (i.e. work/time) / (1/time), you get Work.

In our case the unit of work is Watt-minutes or W'. Somewhat smaller than the kWh, and larger than the Joule, but of the same type. This is what the erg actually measures, and I can't see any harm in knowing the value of what the erg actually measures. It tells us what work we've done in each single stroke. This indeed is the only true thing that the erg tells us, apart from the rating and how much time has gone by.

Using it for a training protocol of course is another question; as with screwdrivers, scalpels and electron microscopes, one has to know how. Mr Caviston in his L4 tables seems to know very well, as did the Interactive some years ago.

Why do you call a unit of work an inverse square pico farad?