Time comparisons between the static and dynamic erg

Maintenance, accessories, operation. Anything to do with making your erg work.
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Time comparisons between the static and dynamic erg

Post by PaulG » August 18th, 2019, 11:41 am

Most of my training is done on the dynamic C2 erg in an attempt to mimic OTW rowing and to potentially minimize injury to my back. It’s pretty clear that the dynamic erg is faster than the static erg but I have not really been able to determine the amount. I have seen one paper (of course I can’t find it now) that said that there was a 10% (?) advantage in the C2 erg on slides compared to the static erg at 2k.
I decided to quantitatively look at this using myself (63 YO LWT) as the test subject and 500 m as the distance. I chose 500 m because I could do repetitive time trials without killing myself and I thought the advantage of the dynamic might be more pronounced at 500 m because you can rate much higher. Another erger has commented that any potential advantage might be greater at longer distances because you won’t have to haul your carcass up and down the slide repeatedly like in a marathon and there would be an energy savings there. Note that C2 doesn’t keep any records for the dynamic under 2000 m.

So I did three paired time trials at 500 m over the course of the summer. Each pair was as identical as possible. Same daily activities, time of day, warm up, drag factor, same two machines, and same amount of rest between time trials. I used the static first in trials 1and 3 and the dynamic first in trial 2.

To me, performance in the 500 m is a matter of expectations. You pick a pace you hope you can hold and then try it. It’s too short to make up for a slow target pace and you certainly can do a fly and die at 500 m if you start too fast. So I picked a pace I thought I could hold for 500 m. Most of my 100 m splits were fairly even with slowing in the last 100 m. I feel each was a maximum effort for the time.

Here are the results with the static compared to the dynamic:

Code: Select all

Trial	         Time in secs (m:s)	                  Watts	            Difference	                   Percent Difference
	    Dynamic	     Static	        Dynamic	  Static	Time	     Watts	               Time	           Watts
1	  98.0 (1:38.0)	98.7 (1:38.7)	   371	   364	  +0.7	-7	               0.71	            -1.92
2	  96.7 (1:36.7)	97.9 (1:37.9)	   387	   373	  +1.2	-14	               1.23	            -3.75
3	  97.3 (1:37.3)	97.6 (1:37.6)	  380	           376.5       +0.3	-3.5	                0.31	            -0.93

Mean	  97.3 (1:37.3)	98.1 (1:38.1)	  379.3	  371.2	+0.73	-8.17	                0.75	            -2.20
It looks like my table got messed up in posting but the average differences were 0.73 Secs faster (0.75%) and 8.17 more Watts (2.2%) on the dynamic.

I think the important finding is that the dynamic was faster in each trial. For you statistical boffins you can see that this is set up to conduct paired t-tests. Due to the consistency in the results any I think any differences would eventually become statistically significant with increased sample size, so I focused on the absolute and percent differences. Average time was 0.73 secs faster and 8.17 W produced on the dynamic. These are not large differences and less than the 10% difference I remember between the static and slides. Due to the power law the absolute difference is greater in Watts. So, I conclude there is an advantage of about slightly less than 1% for this 63 YO LWT at 500 m. It is important to realize that technique is very important on the dynamic and if you get the sequence messed up you will be fighting the machine and the machine will win (well I guess it always does). A newcomer to the dynamic may not have the same results.

The only other anecdotal data I have is a comparison at 1k between the dynamic and static one week apart where I was faster on the static. However, the static test was at a competition and the difference was not that great. I would be interested in other people’s thoughts on if the difference would be greater at longer distances and if they have any data to contribute at any distances. If it turns out that the advantage for the dynamic is greater at long distances I am not going to do paired marathons.

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Re: Time comparisons between the static and dynamic erg

Post by jamesg » August 19th, 2019, 4:54 am

Possibly the simplest way to increase displayed power using kinetic energy savings on Dynamic, slides and water is to increase the rating slightly by speeding up the recovery. Otherwise it's not clear how any energy saved gets into the handle.

This way we could keep stroke length and force as on static or even lighter. Not much more rating is needed, say from 20 to 23 in training and 35 to 45 in sprints, which is easy on slides. I reached 60 and about 500W, but it didn't last long.

HWs might have a big advantage pulling 100m tests on slides or dynamic, so long as they don't come off the rails.
08-1940, 183cm, 87kg. Last seen MHR 162, in 2k (2020-05-16) 8.47.5@24

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Re: Time comparisons between the static and dynamic erg

Post by NavigationHazard » August 19th, 2019, 5:40 am

The late Cas Rekers (died 2010), who developed the RowPerfect dynamic ergometer, evidently tested power outputs on his late 1980s prototype(s) with/without fixed flywheels. He apparently concluded that the 'floating' flywheel on a dynamic erg allowed the generation of some 10-20% more power. Presumably this varied according to the bodyweight of the test subject and also his/her technique. The point is that on a dynamic, you don't have to expend anywhere near as much energy accelerating/decelerating your body weight at each end of the stroke. See http://eodg.atm.ox.ac.uk/user/dudhia/ro ... #section12

The effect of any such power differential on pace is going to depend largely on how fast we're talking. 8 watts (to take the figure quoted by the OP) is about 1.5 seconds of improvement given a starting pace of 2:00/500. It's roughly 0.8 seconds given a starting pace of 1:40/500. etc.

I have no idea whether or not Rekers ever made the power comparison(s) available to the public. Here's a link to a paper he presented on why he thought the RowPerfect approach was a better boat simulator than a static C2: https://www.rowperfect.co.uk/wp-content ... 201993.pdf

Results on a C2 Dynamic (or for that matter an Oartec Dynamic or any other dynamic that may be out there) are going to follow the same general pattern as above.
64 MH 6' 6"

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