How weight affects performance.

[thoroughbred]

How the weight carried by a horse affects performance is a question that is raised from time to time.

Some time ago, in my paper, "Engineering Analysis of Thoroughbred Racing", I analyzed that question.

I won't inflict the mathematics on any of you here; I'll just show the results.

First some comments are needed though:

The math uses the track variant of a horse's previous race to adjust its finish time to what it would have been if the track were normal, i.e., at par.

It also assumes that today's race will be run on a par track.

The previous race and today's race are at the same distance.

The math doesn't include the horses weight only the weight carried, or more specifically, the change in weight carreid between a previous race and today's. This is not a serious limitation as explained in the paper.

A baseline weight has to be chosen. I chose 116 pounds. This choice does not affect the analysis. An equivalent baseline weight would also have sufficed.

The table below shows the results for typical race distances.

RESULTS

Time Change per 1 lb. Weight Change
(Normalized to 116 lbs.)
(Ticks are 0.2 seconds)

Race Distance (Furlongs)-------- Time Change (Ticks)

5.0 --------------------------------------- 0.187
5.5 ---------------------------------------- 0.231
6.0 --------------------------------------- 0.280
6.5 -------------------------------------- 0.336
7.0 ---------------------------------------- 0.398
7.5 ---------------------------------------- 0.467
8.0 --------------------------------------- 0.543
8.5 ---------------------------------------- 0.627
9.0 ---------------------------------------- 0.719
10. ---------------------------------------- 0.930
12. -----------------------------------------1.479
15. ---------------------------------------- 2.716
16. ----------------------------------------- 3.276

Of course, as you would expect, the weight effect is greater, when the distance of the race is longer.

Example: Suppose the previous race, and today's race were both 1 mile, (8 furlongs), and the weight carried increased from 116 lbs. to 120 lbs. Then, with the assumptions made, we would would expect that today's time difference will be:
Change in weight x 0.543
4 X 0.543 = 2.172 ticks
= 0.43 seconds
So 0.43 seconds should be added to the previous time to obtain the estimated, (predicted) finish time of the horse in today's race.

If both weights are not 116 lbs, and/or the race distances are not the same, further adjustments are needed. I leave that as an exercise for the student. <g>

[ceejay]

thoroughbred:

I'm interested in the math. Can you provide a reference?

Is your analysis empirical?

[stuball]

I disagree completely on the weight issue -- I feel it is a non issue except
for 1 situation. That being in Stakes races where there is a big shift in weight
between last race and todays race example ::: Last race : horse a = 123
horse b = 123 === horse a wins ..... todays race : horse a = 125
horse b = 115 otherwise I ignore weight as there are far more important factors
to concentrate on such as speed,pace,class,form, and trainer. If weight were an
important factor how about a muddy day when the horses can be covered with
mud by the end of the race. In my mind impossible to determine what difference
a couple of pounds makes to a 1200 lb horse. mathematics is fine but dont
fall in love with numbers as the horses are animals and the trainers are human.
Well now you have my opinion on this you can ignore it and do your thing as
there is no ONE WAY to win just as ther is no ONE WAY to lose at this game.

Stuball have a nice day !!!!!!!!!!!

[ceejay]

Stuball:

Did you see http://www.paceadvantage.com/forum/showthread.php?s=&threadid=319 back in June?

[thoroughbred]

Originally posted by stuball
I disagree completely on the weight issue -- I feel it is a non issue except
for 1 situation. That being in Stakes races where there is a big shift in weight
between last race and todays race example ::: Last race : horse a = 123
horse b = 123 === horse a wins ..... todays race : horse a = 125
horse b = 115 otherwise I ignore weight as there are far more important factors
to concentrate on such as speed,pace,class,form, and trainer. If weight were an
important factor how about a muddy day when the horses can be covered with
mud by the end of the race. In my mind impossible to determine what difference
a couple of pounds makes to a 1200 lb horse. mathematics is fine but dont
fall in love with numbers as the horses are animals and the trainers are human.
Well now you have my opinion on this you can ignore it and do your thing as
there is no ONE WAY to win just as ther is no ONE WAY to lose at this game.

Stuball have a nice day !!!!!!!!!!!


Stuball:

"Weight a minute", nice pun. I enjoyed that.

But seriously, did I ever, in my posting, say that speed, pace,class, form and trainer should be ignored, and only weight considered? Of course not. As we all know horse racing handicapping needs to consider many important factors.

You say you "FEEL" weight is a non-issue. Feelings are not the best way to refute anything, especially a mathematical analyis. I'm sure you can, AT LEAST CONSIDER the POSSIBILITY that the analysis is correct, and that weight change, should be taken into account along with all the other facors that are important.

In the report, "Engineering Analysis of Thoroughbred Racing" the question of a few pounds added, or subtracted from a, say, 1200 lb horse is discussed.

Aside from that, may I offer up the following to think about. If weight is unimportant, why do trainers look forward to using an apprentice jockey to get the lesser weight that is allowed for an apprentice?

Also, here is something, admittedly anecdotal, that I have noticed. I am in rreasonably good physical shape. We live up a hill from a shopping center. I like to walk, and many times I have walked up the hill to our house, empty handed, and I know how I feel when I do that.

Then there are other times when I purchase something at the shopping center, say a carton of milk, and walk up the hill to our house. I truly notice the difference between walking empty handed compared with the burden of carrying the carton of milk. The milk is only a small amount of weight compared to my weight, yet the difference is palpable.

In any event, the way to refute my argument is to find a flaw in the analysis. Perhaps there is such a flaw. I'm the first to admit that it is possible. But so far, others, including some who are very mathematically inclined, have not found any.

Thanks for your comments; it showed me what more I needed to explain.

You too have a nice day.

[thoroughbred]

Originally posted by ceejay
thoroughbred:

I'm interested in the math. Can you provide a reference?

Is your analysis empirical?

Ceejay:

I answered you this morning, but I see that somehow my message has gotten lost. On the other hand, one of my answers to another member appears twice. Go figure.

Anyway, I'll try to answer you again. The reference for the analysis is in the report, "Engineering Analysis of Thoroughbred Racing."

The method was not empirical.

Normally, the report is included with the CompuTrak program, but if you e-mail your name and address to:

rpbprb@yahoo.com

I'll send you a copy of the report.

[JimH]

Thoroughbred,

I believe you are simplifying the weight issue too much. Remember that the weight that a horse carries consists of three components:
1. The jockey
2. The tack
3. The differential (lead packed into the saddle to bring the weight carried up to where it needs to be)

Every jockey learns how to shift the body position so as to minimize the effect of the body weight on the horse. (Notice that jockeys don't sit on the horse, they crouch in the saddle.) Moreover, some jockeys do this better than others. However, there is nothing that anybody can do about the differential. That lead just sits there, right on a horse's back, and can't be moved. If a jockey can ride at 106 pounds (combined weight of the rider and the tack) and another jockey rides at 114 pounds, if both are riding horses assigned to carry 122, the 114-pound rider is at a distinct advantage! The rider whose riding weight is 106 will have to add 16 pounds of lead into the saddle. That is the weight of a regulation bowling ball! (Try running a mile with a bowling ball strapped to your back yourself sometime and you'll see what I mean.) The other jockey only needs to add an amount of lead equal to that of a shot put. Quite a difference.

I know trainers who will choose jockeys (from among a pool of 3 or 4 riders they regularly hire) based upon what the differential is going to be in that race. That's why every condition book has the riding weight of every single jockey on the circuit.

I make it a point to know how much lead every horse in a race is carrying and it does play into my handicapping.

Of course, any quantification of the effect of weight is purely theoretical. There is no way to know how much faster a horse would have run on a given day if the weight were two pounds less. Sure, he may be three-fifths faster in his next race with a weight shift, but the reason could be almost anything. Horses are living creatures, they are not machines, and do not do the same things every time out.

[karlskorner]

JimH

I have always felt that the DRF should indicate "dead weight" in the PP's (+3, +5 etc.). Your example of the 106 lb jockey carrying 16 lbs. of "dead weight" is a pefect example. Anybody who doen't give "consideration" to that weight switch should rethink their handicapping. You and I have the advantage of picking up a condition book and checking the weight of jockeys, but most of the posters on this board do not have that luxury.

To quote your last sentance "Horses are living creatures, they are not machines and do not do the same things every time out" is something most handicappers fail to realize. To repeat what I have said in the past, the race you are looking at in the PP's for a particular horse, will never be run again, therefore, that "running line" is of little use as a statistic in a DB.

Karl

[so.cal.fan]

In regards to "dead weight", how about Bill Shoemaker?
He only weighed 109 at his heaviest.

[thoroughbred]

Both JimH and Karlskorner have presented some interesting perspectives on weight, especially dead weight.

I have forgotten the name of the jockey, who, many, many, years ago was the first to take advantage of his understanding of how the position of the weight affects the performance of the horse. Perhaps someone can refresh my memory of the jockey's name.

Before him, all jockeys sat in the saddle more or less like leisure horseback riders, that is they sat in the saddle positioned more to the rear than they do today.

The jockey, whose name I can't remember, realized that when a horse is racing, the the front and rear portions of the horse's body rotates about what could be considered a horizontal "axle" of the horse. The typical riding position was such that the jockey's body was located at a place that moved up and down. This meant that the horse was using up energy just in lifting the jockey's weight during the up portion of the up and down cycle.

He realized that if his weight were located at the "axle" position, his weight would not be lifted during the ride, thus conserving that part of the horse's energy to be used for the more important task of winning the race.

When he moved forward to this point and raced that way, I understand that he was mocked, and called the "monkey jockey" because ot the way this unusal position looked compared to the normal position.

However, when it became clear that he was winning more races that way, mockery ceased and now all jockeys try to position their weight like that.

Again, does anyone remember the name of the jockey who started it all?

[so.cal.fan]

I think it was Tod Sloan.

[karlskorner]

So. Cal. Fan.

Bill Shoemaker at 109 lbs. lost "approximately" 80 out of every 100 races he rode in. Maybe "dead weight" had something to do with it, since he rode mostly "high weighted" horses.

Karl