Sunday, April 10, 2011

Pressure Testing at Dr. Hilary Clayton's Lab at Michigan State University

MSU - AT LAST!

Visiting MSU was an amazing experience start to finish. It began as we drove toward the MacPhail Equine Research Facility early on the morning of April 5. The building’s fa├žade and distinctive green roof were instantly familiar from  the group’s online presence and annual reports. I was traveling with RP’s Lisa Jordan, and before we’d even entered the building, we caught each other’s eye and grinned with delight. Some years ago the two of us took Dr. Hilary Clayton’s Equine Biomechanics class (offered through Equinology at the time) and our respect for Dr. Clayton’s intellect, commitment to the principles of research and stunning body of work was embedded in both of us during that course.

THE GOAL FOR THE DAY
We had arranged this trip in order to evaluate the Novel-Pliance sensor mat. This pad has the best reputation as a research tool – and the highest price tag – of any sensor pad on the market and we were eager to see if the result matched the build-up. We arranged to have one upper level  horse and rider, and two school horses present for the testing. All horses had their own saddles. During the course of the day we tested each horse’s saddle and then fit one or two ReactorPanel saddles to these same horses (and under the same riders). We hoped to learn as much as possible about the performance of RP relative to conventional saddles, and at the same time, to learn the capabilities of the pressure testing system so that we could see if the high cost is justified in our application. To help us in our testing, we had shipped a large box of saddles, panels, our special sorbothane rubber discs and a variety of fitting tools in advance.

THE NOW-USUAL DISCLAIMER
The following report is being made to the best of my memory, and with the understanding that I am not a scientist nor an engineer and have only a rudimentary knowledge of how the pressure sensing systems actually work. In addition, we were not permitted to video tape (my preferred method of accurately recording a testing session) and – I admit – the sequence of events were often so fascinating that I neglected to take notes.  I apologize in advance for any factual errors that I am about to commit (I’m sure there will be some). Because we were not allowed to record these sessions, I don’t have pressure sensing maps to show you; I will do my best to obtain these images and permission to put them up here in the near future.

THE NOVEL-PLIANCE PRESSURE TESTING SYSTEM
We began the morning with an overview of the system’s software capability. This session had been set up for us by the Novel-Pliance US staff who showed the utmost professionalism in response to our requests for information, and were the only one (of the four pad companies I contacted) to take our request for a demo seriously. Our experience was greatly enhanced by their presence, especially since Maria Pasquale, an engineer with a biomechanics degree and 8 years of experience at Novel, was on hand to operate the software. Unlike our last experience in which we were left wondering about some of the features of the system, in this case we were given an extremely thorough overview.
The system allows certain data fields to be entered to identify or name each record. These fields are predetermined and are not changeable. However, the next level down in the software permits quite a bit of data entry to thoroughly describe an individual testing session.

When it comes to recording data for evaluation, there are different methodologies. One is to record a certain time frame – say 15 seconds. MSU generally records a certain number of strides. In this fashion, they hope to capture the entire range of the stride in a way that permits comparison. For instance, if one was to do a time trial without counting strides, it is possible that the trial would begin just after – and end just before – the peak force moment of the stride. The longer the test, the less this would have a meaningful effect on results but since pressure tests seem to typically be conducted in short bursts, this could be a factor which impacts the end result.

The Novell-Pliance software appears to be much more sophisticated (to be fair, it might be that Maria is so well versed in operating the software that it simply seemed so).  And the superior data-crunching skills of Dr. Clayton and her assistant, LeeAnn Kaiser, added layers of meaning to the results.

DIRECT COMPARISON: THINGS OF NOTE THAT HAVE STUCK IN MY HEAD

  • The Novel pad scans at the rate of 60-80 times per second as compared to the Team-Satteltest pad at 8-15 times per second.  We don’t know how meaningful this is.
  • The Satteltest pad measures pressure; the Novel pad measures pressure and also measures force. For instance, we learned that a horse with more suspension may generate higher peak forces; this does not necessarily correlate to worse fit. In face, a saddle that permits the horse to move more freely may in fact “cause” (or enable) higher forces.
  • Both pads have 256 sensors, but the Team Satteltest pad has a significantly larger surface area. While this means the T-S pad will work under saddles with a greater weight-bearing surface, it also probably means that the distance between the sensors is greater. The Novel pad does come in a Western version which is longer in both dimensions; we did not see this pad.
  • The Novel pad is smooth; the embedded electronics are almost invisible to sight and feel. The Team-Satteltest pad has sensors which give a texture to the pad. Not sure if this is positive or not but it is a difference.
  • The Novel Pad is “sliced” front and rear so that the pad parts at the wither and again at the loin. The Satteltest pad is a single unit (though contoured for the wither). The immediate benefit to the sliced version is that shear forces of the saddle downward on the pad do not create an artificial registration of pressure on the spine (we saw this in our tests in Oregon two weeks ago). However, the ability to measure pressure on the spinal processes or spine might be very useful. Difference noted. Benefit unknown.
  • The Novel Pad can be calibrated to different scales. The generally accepted scale seems to be 60 kPA (kilo pascals - an accepted measure of force per unit area, one pascal is one newton per square meter). How the Satteltest pad is calibrated – and its scale of measurement – is so far unknown.
  • Calibrating the pad is essential for accurate results. The Novel pad has a calibration frame (at an additional cost and additional procedure). The Satteltest pad’s calibration protocol is so far unknown.
  • Unlike the Team Satteltest system that we saw last week, the Novel-Pliance system does not have a streaming mode (meaning you cannot watch the computer screen to see the pressure testing results as the rider goes around). It is possible to approximate this by recording a session without saving the result which is less convenient but perfectly functional.
  • The Team-Satteltest system includes built-in video: this is a great tool for correlating pressure to results and learning if a high pressure point occurred while the horse stumbled or the rider lost balance. The video for the Novel system is an option that adds thousands of dollars to the cost.
  • Both systems have a graphical representation of the rider’s center of pressure (this is not the center of balance, and is certainly not the center of gravity – we were mistaken earlier).


In (preliminary) conclusion - we believe that the Novel-Pliance system is fantastic in a scientific/research environment. We're not sure yet that it is the best choice for our application, which is to give clear information about saddle fit to people who do not, perhaps, understand physiology, anatomy, biomechanics or saddle construction but who are responsible for making decisions about their horses' welfare. But it is certainly an item of desire for our own use.

NEXT STEPS:
A direct comparison of sensor pads is a logical next step, so that we can learn what, if any, impact there is on accuracy when evaluating the different scan rates, sensor density, video on board, and software in a side-by-side comparison. Daring to dream, I’m imagining another testing day – perhaps back at MSU – where we gather together as many different testing systems as possible.

NEXT POST:
The horses and saddles we tested at MSU, and the results. Hopefully with pressure scans.

2 comments:

  1. Interesting note about the difference between pressure and force! I hadn't thought about that before and am intrigued. I can't wait to read the next post and hear the results!

    Hannah

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  2. just linked this article on my facebook account. it’s a very interesting article for all...


    calibration lab

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