S/Min or intensity

[Islesrower]

I've recently started working out on a C2 and am reading the Rowing Workouts. I am confused about intensity versus strokes per minute. There are many workouts where they say keep the s/min the same but increase intensity. I can change s/min by either rowing faster (moving my legs faster) or by pulling harder. What is the measure of intensity if not strokes per minute?

[Hansink]

...they say keep the s/min the same but increase intensity.

I think this means to row a faster pace (legs faster during the drive AND pull harder) while holding your rating constant.

[Bob S.]

Intensity is best measured by the number of watts, but most forum members use pace instead. The pace (time in minutes and seconds required to do 500m at what ever intensity you are providing) is inversely proportional to the cube root of the number of watts. So a low pace means a high intensity. Almost no one can hold a 1:00 pace (1620 watts) and just about anyone can hold a pace of 3:00 (60 watts).

Bob S.

[bepah]

It has been my experience the the most effiient way to increase intensity and keep it there longer is to push harder with the legs, using the big quad muscles as the power source. the rest of the body then just goes along with the increase at no expanse to energy expenditure from the back or shoulders (or arms, the lease efficient). The SPM can remain the same but the pace increase can be significant.

[jamesg]

What is the measure of intensity if not strokes per minute?

There are two: Watts is the objective engineering measure; the other, subjective, is Heart Rate.

Rating (strokes/minute) is also measured by the ergometer of course, but we can take 60 strokes arms-only a minute and do less work than taking 20 full length.

The erg measures work done per stroke, where Work= net stroke Length x average handle Force.

[mikvan52]

The erg measures work done per stroke, where Work= net stroke Length x average handle Force.

James: I learned something new today. I had no idea that there is a mechanism that measures the length of chain used on each stroke... Is this really true?
I guess it makes sense... except it must be the cog revolutions, & fractions thereof... per unit time.... as measured against the resistance on the flywheel....

[Citroen]

The erg measures work done per stroke, where Work= net stroke Length x average handle Force.

James: I learned something new today. I had no idea that there is a mechanism that measures the length of chain used on each stroke... Is this really true?
I guess it makes sense... except it must be the cog revolutions, & fractions thereof... per unit time.... as measured against the resistance on the flywheel....

it's the angular velocity of the flywheel read using a sequence of tacho pulses from the sensor and from acurately knowing the mass of the flywheel. From that you can get WATTS. From watts you can get pace and calories.

The strokes/min is derived from the shape of the signal from the tacho.

[Bob S.]

it's the angular velocity of the flywheel read using a sequence of tacho pulses from the sensor and from acurately knowing the mass of the flywheel. From that you can get WATTS. From watts you can get pace and calories.

The watts are "real" in that they are derived directly from real physical measurements, but the pace and Calories are fictional, based on arbitrary definitions. Pace is meaningless, since the erg doesn't even go one meter (unless you are jumping around a lot) let alone 500m and the Calories/hour, which by normal definition are directly proportional to watts, have a built in bugger factor of +300Cal/hr.

I don't mean to imply that the pace and Cal/hr are useless. They are arbitrary but, nevertheless, can give us a measure of how hard we are exercising on the machine and how we compare with others. They are just not real values.

Bob S.

[jamesg]

Is this really true?

No; Work = Length x Force is the engineering definition of work done, not how it's measured on the erg. This definition applies universally, for example in the expansion of gases which causes rain, cooling and ensures our ACs and fridges work. Measuring the work we do on the erg and that the flywheel does against the atmosphere is done by measuring flywheel speeds and times and with knowledge of its inertia.

As a curiosity, if we want to know what our average handle force is, we can calculate it from Watts, stroke length (net of the slack) and rating, using 1W = 1 Nm/s.

The Work we do IS in fact the integral of handle travel x force, by definition, but to measure it by measuring forces etc would be expensive (load cells, strain gauges and suchlike) and probably not very accurate. I believe that's how it's done on bikes.