How much does weight really matter?

February 25, 2013 10:56am

Today spawned some very interesting comments on both social media and HRN blogs with regards to the amount of weight carried by a horse in a race. The first group of comments was from a facebook post by Brian Zipse about Bob Baffert’s pending decision to race Game on Dude in the Santa Anita Handicap. The second set of comments was in result to a blog written by Laura Pugh about Violence and Orb’s finish in the Fountain of Youth.


The commonality between both of the resulting discussions can be made around the relevance and impact of the assigned weight a horse must carry during a race. The most frequent discussion point can be paraphrased as, “a horse weights 1100 pounds, and I refuse to believe the difference of a few pounds of assigned weight will make the difference in the outcome of a race.”


Why do organizers control the weight carried by a horse during a race? It could be because they think it will give an advantage to one horse over another, or because they want to feel like they have some level of control on the outcome. I have read that for every extra pound a horse carries it will run a mile race 1 length slower. I have no idea who came up with that, but I guess its just one of those things that has been assumed from decades of handicapping horse races.


Unfortunately, I don’t buy it that easily, so I wanted to find out for myself. How much of an impact of the weight carried by a horse during a race impact the outcome? As it turns out this is not so easy to answer. However, it can be simplified to try and make an estimate.


After lots of thought of how to take the complex motion of equine gait and convert it to something that can be used to model energy consumption, I decided to make some engineering assumptions. The first of which is that equine locomotion can be simplified into an inverted pendulum. It is a mass that is rotating about a fixed point at approximately a consistent distance from said point. I have attached a picture to help describe my key assumption.


Translated out of engineering language, this means that a running horse is just a weight on the end of a stick that is being repeatedly rotated about a point on the ground.




My second assumption is that all horses are the same size and weight (without rider and ballast) and have identical stride lengths. We know this is actually not true, but for the interest of comparing the impact of assigned weight on the race, this vastly simplifies the arithmetic involved. This means that all horses are required to overcome identical aerodynamic forces (more info on that here), ground friction, and body functions (breathing, sweating, anything else the body uses energy for).


Now, back to the physics. I will use the Fountain of Youth with both Orb and Violence as an example. We know the distance traveled (length of the race), the time it took to do so, and the weights assigned to each horse. But as it turns out, the only things that matter here are the distance travelled and the weight assigned. Looking strictly at equations of motion, the speed of the horse is not directly effected by the weight carried.


The problem can be expressed as the number of times the pendulum is rotated during a race (ie. the number of strides the horse takes during the race). The weight comes into play when we consider the force (technically the torque) it takes each time the pendulum is rotated. In terms of horse locomotion, the force I am referencing is the amount required to pull its heavy body over the point of contact on the ground and propel itself to the next point.


So when we know how much force it takes for each stride, and the number of strides taken in the race, we can calculate the amount of energy it took to move the horse a given distance. Based on all the assumptions and complex dynamics analysis above, Violence would have burned approximately 0.5% more calories than Orb during the race due to the added 6 pounds.


Does the weight carried impact the outcome of a horse race? Yes and No. Yes because a horse carrying more weight will have to work harder compared to a horse with lower weight. No because there are so many things that happen from when the gates open to the first horse crosses the wire.


Do I believe Violence would have won the Fountain of Youth over Orb under equal weights? Reality tells me there is no way to ever know. But I am of the opinion that 0.5% difference in energy expenditure is insignificant to the other events that occur during a race. Now if my assumptions above were in fact true, and all other factors of the race are equal, then under equal weights, yes I believe Violence wins. But guess what… no matter how much we try to control the outcome, or think we can control it [by adding weight], we are powerless. In the end, we are all just spectators. Handicap, weight-for-age, or equal weight, the horse that crosses the wire first can simply be called the best horse on that given day.



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Older Comments about How much does weight really matter?...

Really interesting article, Matt. I don't think weight is that important in the outcome of a race compared to other factors (pace, ground loss, traffic, etc.), but a great read.
I know this....Native Diver couldn't carry over 124...Period
Japanese racing forms list the horse's weight race to race in the past performances.
In South America, we pay close attention to weights. Not only to the weight impost, but also to how much the horse itself weighs. When I first came to North America, I felt kind of blind not knowing if the horse's weight had fluctuated and by how much. After many years of being here, I still don't understand why this is not disclosed. Anyway, about the weight a horse carries, I feel that the higher the class and/or the shorter the distance, the less of an impact it has. Also, some horses are more impacted than others by the weight they carry. A couple of pounds may not make much of a difference, but all things being equal, if one horse finished a couple of lengths ahead of another, and now one goes up 4 pounds, and the other goes down 4 pounds, there's an 8 pound difference from their previous encounter, and that may make all the difference in the world. Other factors, such as pace, may - of course - negate that. Handicapping isn't simple math. The weight impost does make some difference, however. If it didn't, apprentice jockeys would get no mounts at all. How many times have you seen a riderless horse "win" a race? And they do it without breaking a sweat because they are carrying no dead weight. Many attribute the popularity of Lasix due to the fact that a horse may lose upwards of 2% of water weight. So, if 20 pounds can make a difference, why not 5, or 10? If I gain 10 pounds of body weight, I'm sure I'd run better than if I had 5 pounds of change in my pockets.
Using your assumption of .5%, that equalis 13 ft at 8.5 furlongs, so that seems just as significant as a bad start, a bump, post, etc
that was a review of 309,700 races
From another source after review of over 200,000 by D. Shwartz....."here we look at the horses ranked by weight carried from highest-to-lowest. There is not much to recommend here beyond horses carrying more weight win a few more races but return less money."
I quoted you the source, go find it and see what it found...And with the featherweights given out today, I am guessing it is far more accurate today.
Ok, i will look at your recomended reading list, seems a computer ought to be able to look at the last 10, 000 races and come up with something.
whatever THEORETICAL aspect you want to use, the stats don't echo them
I would agree it means "next to nothing." I have never hadicapped a race and said " Im not taking the 5 horse cuz he is carryin 6 more lbs." But dont deny the physics of it TV, 6 pou over 9 furlongs must make a few feet difference, its math!
weight mean zip and the imposts horses carry today. Look at how the horses in the Fall Highweight have done over the years. This is a long dead topic as was shown by Dr. William Quirin in Winning at the Races: Computer Discoveries in Thoroughbred Handicapping.
Funny, I've seen footage of Chechnyan rebels sawing a Russian soldier's head-off with a serrated-blade pocket knife and be like, "What's for lunch?" But see Shackleford in the Clark and weep like a baby.
AmbitiousD...I really liked your assesment on "Miracle of Life." She IS trying as hard as any Quarter Horse down the stretch. She honestly brings me to tears with her effort.
Thanks for the kind words and interest in the topic everyone. One of the more interesting parts of racing and engineering I am currently working on is horse shoe materials. If anyone knows a good resource for information of the history or design of race horse shoes, I would be very grateful if you could let me know. And I'm also still researching and building my model to understand biomechanical loads/forces of horse limbs during locomotion. Stay tuned for that one.
To the best of my knowledge only two comprehensive studies on weight added to a horse were ever done. One by Steven Christ who stated, added weight up to 20lbs over 126lbs had no effect. To clarify that would be 146lbs total. The other by Andrew Beyer who reached the same conclusion, but Andy being Andy declared it an anomaly and tossed it out. My own thoughts are, use common sense. If you're a successful handicapper either using weight or disregarding it, why fix what ain't broke. If you're talking about weight then the most important part of the subject never get's attention. What is the actual weight of a horse from race to race, not to be confused with added weight. I personally would pay an extra $20 per form that provided this information as I feel it's so critical, especially at this time of the year when handicapping 3yos. That is a reason I don't make horizontal wagers. If I can't see the horse just before the race I won't wager. If you take the race Matt used with Violence and Orb, pre race they both looked fantastic compared to the rest. Of course there are exceptions, horses that look dull, lathered (Seattle Slew) but that's the random factor in everything. Nice article Matt, as it was more than just a stated opinion coming from a layman.
I did not know my blog sparked such a debate on the weight issue, since i merely mentioned that could be one of several things that contributed to the loss. Those who believe in weight most certainly do. I believe weight can affect a horse, but i think that depends even on the circumstances of the race. 2lbs I don't believe makes a difference, not to a horse as big and strapping as HDG. However, could the two less helped the smaller slighter Blind Luck? Unlikely, but possible. I think the weight could have played a part in last years cotillion, but only because of how the race unfolded. I think that because Questing was made to run slower than her normal pace, allowing MMA to keep closer, allowed the weight to come into play. Had Questing been able to run her opposition into the ground like she did in the CCAO and Alabama, I think the weight would have mattered little. The weight could have mattered in the FOY, because of the circumstances. Violence was close to a rapid pace and moved into it too soon, sooner than he typically is moved. Had he waited and been allowed to run his typical race, could he have won and the weight not even be used as an exuse. Yes. Matt is very correct in saying that weight is one of many, many factors. 2lbs most likely makes no difference. Pace, position, training matter much more. HDG loss because of positioning. She ran away from Blind Luck in the Azeri, in the Del Cap she was wasn't allowed to bound away, allowing BL to see her, meaning she would give it her all to pass HDG. She did, and like she normally would do, she won. Weight can matter, but so do all of the other factors, and it's more likely that they are the cause for a loss or a win, not weight.
Icy knows this quote better, but Cordero thought weights mattered only at a certain level and above. Below they meant next to nothing
Appreciate the attempt to apply some scientific methodology to the subject. However, if you are a trainer or handicapper, you know you consider whether a horse has lasix in your betting decisions. You know that giving a horse lasix prior to a race so that he drops 20-50 lbs gives the lasix horse an edge over a non-lasix horse. I don't bet, but I do know there are not many 3+ horses running w/o lasix, but you know you would never bet the non-lasix horse everything else being equal! This is why overseas trainers give a horse lasix, because if he didn't, he would be at a competitive disadvantage! Also, ask Larry Jones and Porter what they think about the 2 lbs difference between Blind Luck and Havre de Grace 2 yrs ago! Yep, if it walks like a duck, talks like a duck, it's a duck!
How about the fact that maximum weights are literally killing jockeys. Time to raise the weight...

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Meet Matt Scott 

My horseracing journey began when I was 16 years old and my mom took me to Hollywood Park. Although I did not fully appreciate it at the time, the experience stuck with me forever. 10 years later, during one of my many international business trips to Hong Kong, I visited Sha Tin racetrack to watch the races. This is where my true passion began. 


Holding a masters degree in mechanical engineering, the puzzle of handicapping intrigued me. I have made a career of making decisions based on trends, patterns, and formulas, which is why I think I was initially drawn to the sport. However, I have truly learned to appreciate the horses and how magnificent they are as athletes. 


I currently live in San Jose, CA, and when not following racing, I like to spend time with my wife, mountain bike, and design high-speed bicycles that I build and race For reference, 55,000 furlongs is the distance from Hong Kong to my home in San Jose. Also, I have 1-year-old dachshund (aka wiener dog) that I am training to race in the annual Wiener Nationals held at Golden Gate Fields.   


The purpose of this blog is to help give people the viewpoint of a fan that is newer to the sport and eager to learn. I like to respectfully speak my mind, and often the ideas come out of left field, which could give a fresh perspective on a sport rich with tradition and history. hope to represent the many future fans that I wish to follow my footsteps into the Sport of Kings. 

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