Trev wrote:Sorry I don't mean to be pedantic or augmentative but watts don't work like that.
If you are doing 200 watts at 20 spm you are not doing 10 watts per stroke, you are doing 200 watts per stroke.
If you reduce or increase the stroke rate, but hold 200 watts, the force per stroke increases or decreases but you are still doing 200 watts per stroke.
It is a matter of carelessness. If you divide the average watts reading by the average stroke rate you get the average work done per stroke. Unfortunately a lot of people just call this "watts per stroke," ignoring the fact that the stroke rate is in strokes per minute. Somehow the minute part gets lost along the way.
The result of dividing watts by strokes/minute comes out in watt-minutes/stroke. A watt-minute is a unit of work equal to 60 joules. An odd ball unit perhaps, but there are precedents like kilowatt-hours for car batteries and milliwatt-hours for small power cells. jamesq uses the abbreviation, W'. I like that, but the little apostrophe used to denote minutes can easily get lost in translation and is often ignored on this forum.
An erger putting out 200 watts at 20 strokes per minute is averaging 10W'/stroke (or 600 joules per stroke, if you prefer the more conventional unit of work). If he/she can do the same stroke at 30spm, he/she would be putting out 300 watts. For a lot of people there is not much variation in the stroke, so they increase their speed by raising the rate.
Here is an example of training row that I did some time ago, 40' that included a gradually increasing rate and intensity warm up, a steady state middle core, and a decreasing rate and intensity cool down. the last column shows the average work done per stroke in watt-mimutes/stroke. 5 W'/stroke is obviously very weak, but I am many decades past the 10W'/stroke days, so don't expect much.
Date Ended @ Time Meters SPM HR /500m Cal/hr Watts W'/S
40' aio @ UT1
12/15/14 16:59 40:00.0 7678 18 116 02:36.2 615 92 5.11
Split or work interval results
12/15/14 16:59 02:00.0 338 12 84 02:57.5 515 63 5.25
12/15/14 16:59 04:00.0 346 13 91 02:53.4 530 67 5.15
12/15/14 16:59 06:00.0 372 16 100 02:41.2 587 83 5.19
12/15/14 16:59 08:00.0 397 20 107 02:31.1 648 101 5.05
12/15/14 16:59 10:00.0 397 20 119 02:31.1 648 101 5.05
12/15/14 16:59 12:00.0 394 20 114 02:32.2 641 99 4.95
12/15/14 16:59 14:00.0 393 20 120 02:32.6 638 98 4.90
12/15/14 16:59 16:00.0 395 20 123 02:31.8 643 100 5.00
12/15/14 16:59 18:00.0 392 20 127 02:33.0 635 98 4.90
12/15/14 16:59 20:00.0 394 20 127 02:32.2 641 99 4.95
12/15/14 16:59 22:00.0 395 20 123 02:31.8 643 100 5.00
12/15/14 16:59 24:00.0 398 20 123 02:30.7 651 102 5.10
12/15/14 16:59 26:00.0 399 20 124 02:30.3 654 103 5.15
12/15/14 16:59 28:00.0 398 20 124 02:30.7 651 102 5.10
12/15/14 16:59 30:00.0 401 20 128 02:29.6 659 104 5.20
12/15/14 16:59 32:00.0 404 20 129 02:28.5 667 107 5.35
12/15/14 16:59 34:00.0 405 21 130 02:28.1 670 108 5.14
12/15/14 16:59 36:00.0 374 17 120 02:40.4 591 85 5.00
12/15/14 16:59 38:00.0 350 13 114 02:51.4 539 69 5.31
12/15/14 16:59 40:00.0 334 12 107 02:59.6 507 60 5.00
B.