Could I have been mistaken about how to make a rowing shell fast (Part 2)
December 5, 2009 by
Filed under Speed
24 hours after my post on how I have probably been thinking about boat speed wrong the questions that I’ve gotten at the Convention, the questions on email, and the comments have been interesting, and intense.
One question was, “Is this info correct?”
I think maybe, possibly, could be. Certainly needs further investigation. I do know that some of the smartest coaches I know sat down at the table for a demo convinced of one mindset, and a few minutes later were looking at things a little differently. (Some, not all. And that was more due to human nature than to the data.)
Another question was, “What does it mean?”
To me it means that I should take this information and act reasonably upon it. That means to do some testing. Something along the lines of training 1/2 my team with the thought that the finish is the fastest part of the stroke. And at the same time train the other half with the thought that the catch is the fastest part.
Do a pre-test (speed recordings), do some training and rigging, and then do a post-test. Do this in a short window of time (maybe two weeks), see what the effects are, and then go from there.
And I’ll also stay in close contact with Jim and his brains!
And another question was, “What if the info is correct?”
I love this question because of the way it starts, “What if . . .” To me this is a question coaches (and rowers) should be asking themselves all the time, about a wealth of items.
I think the answer to this question, “What if the info is correct?” could be, “Then there may well be a very significant impact in the way we coach, train, rig our athletes.”
Hmm . . . all good questions (not very good answers, yet).
Stay tuned and watch the web for more info. This could be a very interesting topic.
(And thanks for all the great comments!)
Hi Mike, Find the posts interesting. I would still think the finish is the fastest point but of course this could be wrong and no harm questioning it. looking forward to how your experiment goes and hearing more.
Mike, I am curious how the possible delay in gps transmission of speed data in the calculation was handled in the analysis. I’ve noted that impeller diven data from old speed coach is quicker to react than the speed I see from the new gps driven speed coach mobile as well as the garmin forerunner 301 I have used.
@cici: it will be interesting to see what comes out of test.
@ Joe: I have had troubles in the past with GPS delays, however, with newer equipment that may not be as great of an issue (I do know that bridges are an issue)!
Dear Mike,
Please describe what the “new” speed curve looks like throughout the stroke cycle from the powerview data compared to the “old” speed curve from FISA data etc.
Thanks, Marlene Royle
Hi Mike,
I can’t find on either your or his website legible graphs of what is happening so I’m so without the evidence and exactly how it was obtained I am sceptical. I think most other boat speed data are collected using impellers or timed distances to give average speed and accelerometers to calculate the variation (GPS is usually deemed insufficiently accurate for average speed). These data show maximum boat speed during recovery when the rower’s mass is moving backwards and shooting the boat forwards. At low stroke rates (20) the boat speed is highest just before the finish and throughout recovery – the boat drag decelerating the boat is closely matched by the acceleration of the rower pulling on the stretcher in recovery. At high stroke rates (40) the highest velocity is in the recovery just before the catch as the rower switches from pulling on the stretcher to pushing on the stretcher in preparation for the catch see http://biorow.com/RBN_en_2004_files/2004RowBiomNews07.pdf
@Stephen: I understand your skepticism. I would reach out to Jim directly. He was very open with his data and interps. Give him a blast on his site.
I want to thank Mike and all the other coaches for sitting down with us at USRowing and reviewing the data. As a general comment, we put the storm symbol in the PowerView logo as we knew the information would cause a storm. From my 30 years in the sport, I know rowers and coaches have firm and unchangeable beliefs. Nonetheless, the concept behind PowerView was to give the coaches a tool – to do post practice analysis – and to allow them to monitor their programs over a season. Once we started to collect data, from Masters to Elites we started to see patterns develop that were not consistent with some of the literature. I can assure you that once I saw these patterns, I had the same response as some of you. So we tested the equipment to be sure that the data was correct. There is a video posted on YouTube (look for PowerView) of an elite eight. If you listen to the coxswain as he calls out the splits and rates; we are consistent. We tested boats at the Head of the Hooch and the timing was consistent with their posted time. Further we have performed session, recording the speed coach at the same time we collected data, and used other mechanical devices to check system components. Further non-rowing tests were performed to make sure the system was accurate. It is accurate. We checked our math and our code.
It is the combination of video and data that is important. What does a typical video show? From the catch the boat speed and the accel data both spike to the negative. We see speed for example dropping from 6.3 m/s to 4.8 m/s. The negative spike ends at or past the mid-drive, where the boat begins to accelerate until the Finish. When the bodies are over and the wheels begin to move, the boat re-accelerates to the catch (at higher rates). Throughout this stroke the accel data (no possible lag here) and the speed curve are totally consistent. We also look at other component such as vertical lift and set and see the impact that it has on boat speed. All of this is consistent. In fact if the Speed Curves were different it would suggest that you are putting a negative force on the boat and the boat is increasing in speed. Now that would be interesting. You could see the same data but without the synced video come up with a different conclusion.
What the data shows more then anything is that the absolutes are not really absolutes but are more highly variable. The issue of “does the boat continue to accelerate after the release” is a good example? From the sessions – where we have collected data – it would suggest this is the case in higher rate pieces but not in lower rated steady state pieces. This is consistent with StephenA cited article. However, the breakpoint is dependent upon the individual crews. The combination of synced high quality video, GPS and accel data shows, that boat speed is highly variable, based up weights of the crew v weight of the boat, hull design, stroke rate and technique. Would that happen with your lightweight junior girls eights? Don’t know, we have not tested one.
These speed curves are very unique. There is a radical difference in the curves between sculling and sweep, with the decel from catch to mid-drive much higher in sculling (1X and 2x – we have not looked at 4X). There are significant differences between for example a 4- and an 8. The curves are so different that it calls into questions how you rig and train your rowers. WE ARE NOT MAKING ABSOLUTE STATEMENTS HERE. PowerView is a tool that allows you as a coach to collect data and as you adapt your rowing style, monitor the impact on boat speed. I would suggest that before you buy a new boat that you test your crew with the hull to see how it will impact your speed. Yes we are going to work with a variety of rowing programs to further determine the true nature of the stroke and to make some general statement. The Generalized Statements are where you can get yourself in trouble. It is up to the individual coach to determine what works best for them and that requires that you purchase a PowerView System and use it (OK that my Sales Pitch). As coaches we have not had this capability before but now you do. How you use the system to increase your boat speed is up to you. What nuggets you find, might be the difference from the C Finals to the Medal Podiums.
If you want to try a system out, I am setting up a variety of tours, I will be happy to record your rowers and then go through a quick analysis. If you are planning a winter training session, I will be in FLA, South Carolina and San Diego in January.
My direct email is jmitchell@integrature.com and you can call me at 703.973.9209.
Thanks
Jim
I love this kind of inquiry and discussion because it makes us all think!
I have spent many hours contemplating (without any data)the difference in the way a loaded trip canoe moves compared to an unloaded one. To maximize speed you have to change the way you paddle; the momentum of the loaded canoe requires less of a quick catch to keep it going (once it is “up to speed”).
This is all about displacement,load, etc.You can actually feel the canoe losing speed through the recovery.Keeping a 6 man Outrigger canoe going at top speed requires a different catch and stroke than a OC1 or OC2
I would love to see more thoughts following, “if this were proven to be true” what then?? Everyone knows that if you “zip” up your slide in a stopped boat, the boat will move forward.. Hmm maybe we should go back to rowing the “American” style- fast out of bow, creep up the slide to the catch
What was your final conclusion after escaping the Convention?
What did Kevin say in the level III session??
Wish I had been there..
Cheers
I don’t have it in front of me right now, but the Karl Adam lectures at South Alabama compiled by Dennis Kamrad in ’72 also had technical data and graphs showing the boat speed variations on drive and recovery, with Adam saying he had his oarsmen accelerate all the way up the slide into the catch in order to maintain a constant (and maximum) boat speed. I’ll re-read tonight.
From Ratzeburg Rowing Clinic, Princeton, Oct 9-13, 1970 as compiled bu University of Alabama, Huntsville, on p. 56 Karl Adam states:
” There is a diagram which represents the speed curve of a boat during a single stroke.” (Adam has a diagram with a sine wave shaped like two equal hills separated by a valley of equal size, with the Catch E about 9/10 of the distance down the slope of the left “hill” and the finish A–where the slide begins to move–about 1/10 of the distance starting up the right hill. in between is the “valley” where the boat is moving the slowest with average boat speed represented by a straight horizontal line equidistant from the tops and bottoms of the two hills. Sorry–have to send a picture to describe better and haven’t got a gravatar handy…Andy).
Adam continues: “Strangely enough, the boat reaches its maximum speed not during the stroke, but when the slides roll forward. It is good to keep the speed curve of the boat as flat as possible because the resistance of the water to the hull of the boat quadruples as the speed of the boat doubles. One comes to the following solution: At the point where the line “A” is drawn through the curve, the slides begin to roll forward in the boat. One should try to reduce the peak of the speed in the boat. If one rolls forward as fast as possible from the finish, one gets in the speed of the boat a peak which is high but short. I will now direct oarsmen to begin rolling forward slowly and to speed up rolling in proportion to the amount of energy which is used by the resistance of the water to the hull of the boat. The slide is rolled forward in proportion to the amount of the boat’s speed which is wasted in overcoming the resistance to the water. In other words, as the boat begins to slow down due to the water resistance, the slides roll forward faster. This increase in the speed with which the slides roll forward in the boat makes up for the amount of energy consumed by water resistance. In this way a speed curve without great variation can be obtained by the boat.”
@ Andy: That’s good stuff. Thanks. I’ll make sure that I send it along to Jim Mitchell. Appreciated.