More E-Trakka Innovation: Stride Length Captured During Workouts

etrakkaGPS

Adding yet another dimension to understanding your horse’s performance, Etrakka has formally introduced the metric known as SL50 – stride length at 50kmh (31mph, or 14.8sec/furlong). The new GPS antenna also will allow you to view stride length at peak speed; something that is becoming ever more common at 2yo in training sales.

To date: several hundred measurements of SL50 have been taken ranging from 18-23ft, with the average score sitting right at 20 feet. As expected, elite horses average readings come in at just over 21.3 feet. How do your horses measure up?

This link takes you to some info from the manufacturer; including a neat comparison between 2 horses with identical HR/GPS responses to exercise – however a superior stride length made one a millionaire:

http://etrakka.com.au/wp-content/uploads/2013/07/E-Trakka-stride-length-summary.pdf

Some barns are looking for reasons to keep a handsome, well bred young colt – and yet others are looking to cull stock. Stride length can provide a valuable piece of information when making those difficult choices.

Bringing along some youngsters and hoping to avoid downtime due to shin soreness? Checking these figures during each workout is crucial – as you can catch the very first instance of a shortening of stride – as little as 1.5 feet, that can be one of the very first signs of problems. Perhaps you are then looking at 2 weeks of rest, as opposed to 2 months-

SecretariatSA

A while back someone had posted this link on my Facebook page about Stride Angle:

http://www.somaxsports.com/photo.php?analysis=SecretariatSA

The great Secretariat was thought to have a stride length at peak speed of just over 25 feet, which may be larger than all the greats save Man O War – however the link above shows him to have a very large stride angle (110 degrees). Conversely, Seattle Slew had a small stride angle of just 88 degrees.

While some of the measurements featured here could be open to debate, the main point is that when you increase stride angle by 1 degree you improve stride length by 2%. Think shoeing, think massage work, think uphill gallops – all ways to increase power and range of motion – leading to an improved stride length – the Etrakka can help you quantify and analyze this variable during your conditioning regimens. Find out what is, and isn’t, working.

Save time. Save money. Win races.

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About bpressey

Equine Exercise Physiologist

Posted on July 29, 2013, in Uncategorized. Bookmark the permalink. 5 Comments.

  1. Bill,

    The best study done on this area in racehorses is “Locomotion evaluation for racing in Thoroughbreds”. Barrey et al. 2001.

    In terms of velocity, yes Stride Length and Stride Frequency was positively correlated to velocity. That is horses, got faster by increasing their stride length and stride frequency.

    However, in terms of performance, Stride Length is actually negatively correlated. Stride Frequency is what is important. Horses can have long strides, but if they cant maintain a frequency then they are just slow horses. Equally, horses with smaller strides, but greater frequency can win good races.

    Thus, while the measure that E-Trakka has developed is a good one to track against velocity, it is not a good metric to use against for class.

    They are close however, I would think that Heart beats per stride @ 50kph would be a much more significant metric for metabolic cost of transport and more accurately discriminate for racing class.

    Byron

    • Thanks Byron-

      I, too, would caution against using stride length as the sole factor on keeping/culling a prospect. But watching that metric over time in an individual could be a valuable trendline. You echo my thinking exactly with regards to HR/stride. In the past I have broken it down to feet per beat, making sure to stay around 200bpm or lower.

      I would assume stride frequency is only evaluated via high speed video? One of my clients uses the Dartfish application in such a manner. He can take a race replay, overlay it into his software, and calculate stride frequency of horses before he claims them. Not surprisingly, he is a former Olympic caliber sprinter.

  2. They would already have stride frequency (distance/stride length) so it would be easy to do some average stride frequencies per 200m/furlong into the program alongside the velocity & HR which they already have.

    I am aware of the stride frequency program that you talk about. That, I believe is part of the fatigue curve analysis work that was done by Jeff Seder and Steve Roman. It relies on horses running slow last splits (which is dirt racing and how speed figures work) to work out the better horses based on those that are still maintaining consistent stride frequency.

  3. Bill,

    Interesting stuff, but there is also surely a question of economy of effort and sustainability that comes into it. The Green Monkey would have obtained an impressive peak velocity, but was doing it in a way that was completely unsustainable.

    I would think the same could apply to stride length. To go faster you either have to increase stride length or stride frequency, or some combination of both. Either, I would think, increase the cost of effort, so you would either have to become fitter to maintain the increased stride length (assuming frequency was constant), or you would tire quicker. I would guess the goal is really optimal stride efficiency at a given pace.

    • Hi Alan-

      I’m thinking more of using the SL50 data during the conditioning process, as opposed to a sales tool. I agree 100% that efficiency of movement (distance covered per unit of effort) is the biggest predictor of success. Take the 2 minute lick/15 sec/furlong as our given pace. Now we have SL50 to add to HR, adding yet another dimension. Together we get both stride and aerobic effort, or metabolic ‘cost’ of that stride.

      In the example cited here in the Etrakka link, you had 2 identical horses in terms of HR and GPS behavior, but one had the superior stride – all else ‘under the hood’ was equal. Without the stride knowledge obtained during the training mornings, such a horse may be placed incorrectly into races.

      Another angle: I think someone told me that in the 2yo sales, breezing on Polytrack increases stride length by 4 inches on average at peak speed. What if I have a horse I am thinking about racing at KEE, but his training shows only a 2″ improvement in SL over the KEE surface? Regardless of pedigree, don’t race him.

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