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[RC] The Physics of Weight Divisions - k s swigartBruce Weary said: I have a hard time understanding why people think horses are somehow magically exempt from the laws of physics, when it comes to carrying weight. Probably because the people who are propounding about it have virtually no understanding of (or if they do they forget to take it into account intentionally to promote their personal agenda) the fact that the weight of the rider is but one (and a fairly irrelevant one by comparison) of the many variables that contribute to how much work a horse must do in order to propel its entire load (i.e. not just the weight of the rider and tack but the weight of the horse as well) forward down the trail. And that how much work a horse must do in order to propel its entire load down the trail is but one of the many variables that has an effect on the outcome of the event. Yes, physics says that, all other things being equal, there will be more work performed with a heavier rider. But since there is no way for all the other things to be equal, the differences in rider weight pales in significance. It is downright silly to handicap for just one of these multitude of variables, especially since, by comparison to the other variables, static rider weight is pretty insignificant. Why is a standard minimum weight often 165 lbs for some bigger rides? Tevis USED to have this minimum weight requirement (probably because a naive and short-sighted somebody thought "physics says that rider weight ought to have an effect on outcome") until somebody else (Susan Garlinghouse) did a controlled study attempting to correlate outcome with rider weight and found that there was no correlation (although she did find some correlation between the entire load and incidence of lameness, which suggests that heavyweights may be inadvertently reducing their chances of success by making the mistake of choosing a big horse). While it is true that correlation does not necessarily imply causation, it is also true that lack of correlation DOES imply lack of causation. And, incidentally (and scads of data exist to support this), there is no correlation in flat track TB horse racing between rider and tack weight carried and outcome. Race tracks around the country handicap races with rider weight carried, because most people in the betting public are foolish enough to think that weight carried has a big effect on the outcome of the race, and if you want lots of people to bet on the outcome of the race you need to get people to think that all the horses might have a chance. The other way that race tracks handicap races is by having horses run "in their class" (and there are some pretty strict rules about this), and since classifying horses (e.g. claimers, allowance, stakes horses, etc.) takes into account all the other variables besides rider weight, you would think that rider weight WOULD have a bigger effect on outcome, but there is still no measurable effect (of course the variation in weights is usually between 3 & 5 pounds, a fraction of the weight of even the horse's breakfast, so only a fool would think that this might have a measurable effect on the outcome). Could it be because anyone carrying less than that has an advantage? Nope, it is because some people are foolish enough to think that anyone carrying less than that has a measurable advantage because it seems like it ought to, or because they never actually took enough physics to realize that the mechanics of load bearing are far more complicated that standing on a scale (and when you add movement into load bearing it becomes even more complicated). Chances are that many of the people who think this never took any physics at all. Since I vividly remember the first assignment in my first quarter of high school physics was a bridge building exercise where everybody in the class was given the task of building a bridge that spanned 8" (I think) to be made out of 55 of a specified brand (don't ask me which one, it was over 20 years ago :)) of toothpicks and Duco Cement (I do remember the brand of glue). There were rules with respect to how you could use the glue, etc. but the assignment was to make a bridge that would hold up the most amount of weight (it was a bridge design exercise, but it was also designed to get us thinking about the effect of force vectors on load carrying). Judgement day was when we all brought our bridges into class, and each spanned them across the gap between two desks set at 8" apart, stuck a metal rod through the middle of it, hung a bucket off of it and kept adding weight until the bridge failed. The bridge that failed under the highest weight was able to support more than FIVE times the load of the bridge that failed under the lowest weight. The difference in load carrying capacity of these bridges was orders of magnitude, despite the fact that length and materials were very strictly controlled for. Far more controlled for than the assorted variables associated with the construction of the bridges (from a mechanical physics standpoint, that is what a horse's back is) that are our horses. What I learned in all the subsequent physics (and engineering) classes that I took is that, while the design and placement of force vectors alone can have a huge impact on the ability to support a static load, when you start introducing differences in materials and size, etc. the ability to support a static load is impacted even more, and that when the load becomes dynamic (i.e. moving) instead of static, the ability to move that load is impacted yet again more. People who think that the laws of physics say that the weight of the rider must have a measurable effect on the outcome of an endurance ride either never took physics or weren't paying attention during the first week of their first class. It isn't magic that the static weight of the rider and tack bears little effect on the outcome of an endurance ride. It is just that the differences in static weight are so minor in comparison to all the other variables that affect the outcome of an endurace ride that it gets lost in the noise. The reason we have weight divisions in endurance and that race tracks have weight handicaps on flat track racing is that few people understand the physics well enough to understand why rider weight has no measurable effect on outcome, so they think it ought to. If anybody who does understand it tried to really explain it (rather than giving anecdotal stories from high school physics classes), most people's eyes would glaze over with incomprehension because the physics associated with how multilevered mechanisms move variable loads over uneven terrain across time is EXTREMELY complicated and cannot, in any reasonable way, be reduced to "have the riders stand on a scale." kat Orange County, Calif. =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Ridecamp is a service of Endurance Net, http://www.endurance.net. Information, Policy, Disclaimer: http://www.endurance.net/Ridecamp Subscribe/Unsubscribe http://www.endurance.net/ridecamp/logon.asp Ride Long and Ride Safe!! =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
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