DPS decrease with higher rating?

[bobkwan2007]

Lower ratings I average around 8.5 to nine strokes per 100m (rough estimate. At higher ratings, let's say >25, the number of strokes goes up, i.e., the distance per stroke decreases. Is this a common thing? Is it ideal, or even possible, to keep this power curve linear? Or is it more like the power curve for a car engine--rpm vs HP?

What are your thought?

[hjs]

Lower ratings I average around 8.5 to nine strokes per 100m (rough estimate. At higher ratings, let's say >25, the number of strokes goes up, i.e., the distance per stroke decreases. Is this a common thing? Is it ideal, or even possible, to keep this power curve linear? Or is it more like the power curve for a car engine--rpm vs HP?

What are your thought?

Simple answer: no (keeping everything else the same)

It's just you like you say yourself. It's a simple low of nature. The lower you rate, the more power per stroke you can give because the rest after each stroke is longer.

[gregsmith01748]

I see exactly the same thing. Here's my data.

SPM, Split, MPS
33, 1:39.6, 9.2 (500m interval)
28, 1:49.6, 9.8 (2K interval)
24, 1:56.1, 10.8 (60' PB, not rate capped)
20, 1:59.7, 12.5 (60' rate limited at 20 SPM)

Doing L4 workouts is even more pronounced
16, 2:05ish, 15
18, 2:02ish, 13.5
20, 1:58ish, 12.7
22, 1:54ish, 12
24, 1:50ish, 11.3

Some folks advocate using a metric called SPI (Stroke Power Index) to try to normalize for the effect, but most of the folks on this forum find it pretty bogus, since it is basically impossible to maintain the same SPI at high rates as low rates.

Now I am focused mainly on hitting what I think should be the right stroke rates and then working against time on distance pieces or distance on time pieces. All the other stats are fun to look at but don't seem to provide much in the way of guidance for me.

[bobkwan2007]

Some folks advocate using a metric called SPI (Stroke Power Index) to try to normalize for the effect, but most of the folks on this forum find it pretty bogus, since it is basically impossible to maintain the same SPI at high rates as low rates.

I've seen SPI on this forum, in one particular thread, but I never really fully grasped the concept. But hjs is probably on the money with the longer rests resulting in more powerful stroke for lower rating.

So to get faster, what should one work on? Increasing rating or increase DPS? Which is more efficient/easier?

[Bob S.]

So to get faster, what should one work on? Increasing rating or increase DPS? Which is more efficient/easier?

Yes.

[gregsmith01748]

I think most training plans are working to increase your distance per stroke. Essentially, the more power per stroke you put in, the fewer strokes you take and the less energy you waste dragging yourself back up the slide.

Over time, I think most people end up going faster at the same stroke rates, which is an increase in DPS, rather than rating higher as they train. It certainly was the case for me.

[Carl Watts]

I think most training plans are working to increase your distance per stroke. Essentially, the more power per stroke you put in, the fewer strokes you take and the less energy you waste dragging yourself back up the slide.

Over time, I think most people end up going faster at the same stroke rates, which is an increase in DPS, rather than rating higher as they train. It certainly was the case for me.

Correct. When your new on the Erg your DPS is in the single digits, typically 8-9metres. As you improve, no only does your pace increase for a given spm but if fact if you work on a lower spm for a given pace your DPS goes out to like 12-13 metres. In short if someone is rowing beside you at a lower rating while still maintaining the same pace and they can keep it going, they are a better rower. It is harder to keep rowing at say 1:58 pace 15spm than it is 1:58 pace 18spm.

[gregsmith01748]

Hell, I'd be happy to row 1:58 at 18 spm. I can only do that for a few minutes before I keel over.

[jamesg]

So to get faster, what should one work on

Technique, because speed comes from technique, and maintaining that speed from fitness. Technique means full length firm strokes, taken from a strong catch position well forward with your weight on your feet. Such strokes are hard work, which is what makes us and boats go fast and also trains us, so don't do too many per minute, but do large numbers of them at all power levels.

Low drag is essential, so that the pull can be quick and the recovery slow.


SPI is the right idea, but something of a misnomer: it is Work. The ergometer measures work done per stroke using speed and time data from the flywheel. Work done evidently = net stroke length x average handle force. We can estimate our work per stroke from the on-screen numbers, dividing Power in Watts by Rating. There are no fixed numbers, as it depends on age, sex and height. An Olympic LW can pull up to 12W' at 40; anything below 5 and we're hardly rowing at all. FWIW I use 7.5 to 9 according to the length of the pieces. As I row at mostly 20-22, this gives me 11-12 m/stroke and 150-200W. In general if you pull at >2W/kg body weight and you travel more than 10m/Stroke, you're ok. However not even Olympic oarsmen can go 10m at rating 40 in a 2k.

From an engineering point of view, Power = Work done per unit time, so has dimensions Work/Time; Rating has dimensions 1/Time; dividing Work/Time by 1/Time, we get Work.

The erg calculates speed from Watts where W=kV^3, using a cube law to mimic boat speeds. So to double the speed, we need to deliver 8 times as much Power to the handle. The decreasing metres per stroke with rating increase comes from this.

[LincolnB]

To me, as a lightweight, it is simple. The heavyweights row faster than the lightweights. Even the middling heavyweights row faster than the best lightweights; it's not really close. Their extra mass doesn't make their technique any better or their fitness any better. They really don't row at a higher rate either. They can row faster because they can put more power into every stroke. So if you want to row faster, then row like people who are faster. Put more power into every stroke.

[ThatMoos3Guy]

Well, as others have said, when there's less time between strokes there's less time for the boat to run out. The other issue comes from the fact that the relationship between boat speed and power isn't linear; as speed increases there's a much greater increase in power needed.

For example, 2:00split at 20spm is about 10spi, and 12mps. 1:45 at 30spm is also around 10spi, however it's only 9.5mps.

The Wolverine Plan spends a lot of time on working at developing strength at low stroke ratings and then carrying that power as the ratings increase. You can only rate up so high, if you're rating in the mid to low 30s for a 2k it's going to be hard to drop time by increasing the rate. There are of course outliers (lightweight world record was set at 40spm), but for most normal people increasing the power of each stroke is the best way to improve. Of course, if you're like me and rate 28spm for a 2k then you also need to work on increasing that.

[luckylindy]

It is possible for you to keep this power curve.In my view many of the training plans are working to increase your distance per stroke.It is because of the fact that the more power you put on each stroke,the fewer strokes you take and as a result you waste less energy.

It's only possible to maintain the DPS as you increase your rate if you also greatly increase your power output. Doing both simultaneously would be tremendously difficult. For example, I can row for a few K at 20SPM and 1:50/500. This correlates with a 13.6 DPS and 263 Watts. If I were to maintain 13.6 DPS at 30SPM, I'd be cruising along at ~1:15/500, which is over ~800 Watts. I might be able to pull that for one or two strokes, but it doesn't seem reasonable (in general) to expect DPS to remain constant as SPM increases.