Thursday, November 16, 2006

More on Erg vs. Boat

As a result of my last post on ergs vs. boats, Aaron Benson posted a comment in which he noted that the difference between footstretcher and handle force comes about because "a stationary ergometer requires the rower to accelerate and decelerate the mass of the upper body at both ends of the stroke in order to reverse direction." He goes on to point out that this "disparity between footstretcher force and handle force can be minimized by rowing on Slides, or by using a RowPerfect ergometer."

This comment reminded me of several discussions I've had about how much of an advantage a rower gets from erging on a slide vs. without a slide. The consensus is that because of the effect Coach Benson describes above, less energy is required to go up and down the slide so a rower should go faster on an erg on slides. Apparently there is a study by Fritz Hagerman that I've seen referenced but haven't actually read, that shows more energy expended on slides as measured by heart rate. This is counterintuitive, however, and it's not clear why would be so. I also recall reading that the benefit mostly shows up in longer pieces (longer than 2k). I can't find either of these studies online or I'd link to them here (if anyone has them let me know).

Another factor that comes into play with slides (or the RowPerfect) is technique. The point of slides is to simulate an actual boat so it seems reasonable to think that a rower with better technique would benefit more from a slide while a rower with poor technique might actually suffer (banging into the ends, etc.). I've seen both. This all raises an interesting question - could you seat race on land by rigging together two sets of eight ergs on slides and looking at the average "boat" time (the monitors can be rigged to do that)? Better than single, static ergs, but still not a boat. Now if we could just put the ergs on slides on top of telephone poles laid on the floor... Oh heck, maybe we should just get in a boat.


Anonymous said...

one thing your idea for seat racing doesn't take into effect is weight. Although this may work for most lightweights if they are all around 130, you wouldn't be able to compare people of different weights.

Also, although slides may simulate the momentum of a boat, everyone knows there is a big difference when you try to hit ratings. A slide erg will let you row at a rating 2-4 beats higher than what you might hit in a boat.

JW Burk said...

Yes, I agree with you on both points. Part of the explanation on why higher rates are easier has to do with the fact that an elastic cord helps bring the handle back on the recovery on the erg while in a boat you actually have to move it yourself.

Aaron Benson said...

Actually, research has shown that it is not possible to sustain racing stroke rates on a stationary erg. One of the reasons a mobile platform was developed by researchers in the eighties was to enable rowers to practice at the rates they would use in a 2k race.

I have found that rowers doing 1000m pieces at their 2k pace will row 3-5 spm higher on Slides.

alpha said...

I think that without slides your rating is impaired by about 2-4 spm, through having to accelerate and decelerate the body?

However, I believe that heart rate is higher on slides because of the increased rating. In this sense the work measured in Watts on the erg isn't an accurate comparison between ergs with and without slides. Higher rating has been associated with higher rating for a while and has led to some crews favouring higher racing ratings. In this respect, using heart rate to measure work also seems to be a poor comparison of work.

Anonymous said...

I don't see many people pulling 2k's at 36+ on stationary ergs. It's pretty easy to tell that slide ratings are mroe in line with on water ratings than the stationary erg.

Alan Thomas said...

I love a good discussion and considering where different changes like this can take us. So it is interesting to read here everyone's opinion.

However, your "Oh heck, maybe we should just get in a boat" remains to me the best - the slides might be affected by technique but certainly not all the components of good rowing technique - bladework to name just one, not to mention one reader's comment here about weight.

Alan Thomas
Rowing Science Weblog