2k Power/Weight Ratio

Question
I have been rowing for 18 months and, with regards to a 2k test, my coach likes to talk about the 'power-to-weight' ratio. I'm a 5'11 female weighing 154lbs. Regarding these details, what would be a 'good/great!' 2k score? Thanks.

Answer
Hi Amy: Power-to-weight ratio suggests your power (in Watts) can be simply divided by your weight (in kg) to adjust erg scores.  However, The Physics of Rowing web site points out that it is more accurate to use the "cube root" of weight. The site doesn't explain why this is, but my guess is power:weight ratio does not change directly with increase in weight.  

Calculating a power:weight ratio would be done as follows.  Take 2 rowers, Ernie and Bert.  Ernie weighs 100 kg; Bert, 70 kg.  Both rowers do a 2K piece.  Using the Performance Monitor, we want Watts vice 500 split, we see the following results

Ernie = 442W
Bert = 408W

Divide each by the cube root of their masses to get:

Ernie = 95.2 W / kg^(1/3)
Bert = 99.0 W / kg^(1/3)

In this example, While Ernie pulled a better time, Bert has the better power:weight ratio.  

The Concept II website also has a weight adjustment calcualtor, which pretty much tells you the same thing.  You can find it here.

http://www.concept2.com/us/interactive/calculators/weight_adjustment.asp

Regards/AP