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Stride Angle in racehorses - fact or fiction

June 18, 2015

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In my last post I alluded to the angle of the stride of Frankel by talking about the 'extension' that he seems to have and the lack of curl of his foreleg. I received a couple of emails about the "stride angle" of Frankel and how it might compare to Secretariat.

To be honest, I didn't know too much about this so I googled (is that a word?) away to see what was being referred to. The basis of the concept seems to come from the work of Bob Prichard at a company called Somax Performance Institute. Mr Prichard's posit is that through motion analysis and what he calls "Microfiber Reduction" he can improve speed and efficiency of motion but also that there is a corrleation between stride length and stride angle.  You can read his work by clicking on the link here and there is a Youtube Video on this

 

 

I will say this before I go on, the camera angle differs widely in the examples that are given on the Somax Performance page and the part of the cycle of the stride that the measurement is taken also differs (take a look at Secretariat and Affirmed as examples) which will lead to vast differences in angles and what can be said or not said from the data.

 

Last year Mr Prichard put out a press release stating that California Chrome has a stride angle of 100 degrees. Mr Prichard went on to further say......"The reason that the stride angle is so important in racing," explains Prichard, "is that for every degree you increase your stride angle you increase your stride length by 2%. This means that Chrome is covering 14% more ground than Affirmed, but 20% less ground than Secretariat. The stride angle is basically determined by flexibility. For this reason, we expect its long term performance to be somewhere between Barbaro and Affirmed."

 

I'm calling bullshit on that one. If Chrome has a 20% less stride length than Secretariat and we know that Secretariat's stride length is 24.5m then Chrome would have a stride length of just 20m (20% less than 24.5m). Firstly, unless you are a quarter horse a 20m stride length isn't going to cut it at the highest level and secondly, we've measured the stride length of California Chrome at 7.51m/24.6ft which is almost exactly the same as Secretariat.

 

Still, setting this statement aside I was interested enough in the concept to at least see if there was any weight to it and thankfully I have the data to test it. I have a lot of high speed video of horses at two year old in training sales for the past few years so I gathered 10 elite racehorses and another 23 horses that had had at least 30 starts and had proven that they couldn't get out of their own way.

 

Firstly, to make sure that we have repeatable data, I measured the horses at the exact same point of the stride cycle, when their near fore leg was at vertical stance.

 

 

 

From there I used my trusty Kinovea video editing software to measure the stride angle, just as Mr Prichard had done on his web site. I made sure that the line measured came from the fetlock, through the line of the leg and that the point of the angle was right behind the saddle. Here is Bayern as an example.

 

 

Below are the results for all the horses measured sorted by Stride Angle.

 

 

 

Another takeaway from this small pilot study was that if you moved the points determining the angle just slightly the difference in overall angle was quite large. Horses could have a 5 degree swing if not completed correctly and in a repeatable manner. You'd have to also think that the original data of Somax where they stated Man O'War and Seattle Slew having stride angles in the 80's is completely ridiculous as there wasn't one below 100 on the list of horses I did.

 

I am going to have to put the concept of Stride Angle in the "fiction" basket. However, like a lot of things in this game (the X factor being a shining example), I suspect that this one isn't going to die despite the evidence to kill it.

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