While I was on one of my usual bike rides this weekend, I
started to think that there is a significant factor in horse racing that I have
never seen addressed. In a sport
where any slight competitive edge could me the outcome of a race, one key
variable is being severely overlooked.
Look at the world of professional cycling, where teams and bicycle
designers invest millions of dollars to make the bike and ride as aerodynamic
as possible, and where even a 1% gain of efficiency can mean the difference
between victory and defeat. It
puzzles me why horse racing has not yet adapted the techniques applied in so
many other competitive racing sports.
As I watch horse racing, one key thing stands out to me that
I have not been able to answer. A
good example is Gary Stevens on Silver Charm in the 1997 Belmont Stakes. Why is it that some jockeys stand so
much higher than others while their mount is running? Is it to get a better viewing angle, to keep
balance, or is it simply the most comfortable position? In reality it is probably all of these
things and more. But when I watch
a jockey stand tall on a horse vs one that is in a tight tuck, I wonder how
much of a difference this really makes in races that usually last less than two
minutes.
I decided to actually calculate the aerodynamic losses of a
horse and jockey for different “stand-over heights.” The force of aerodynamic drag
is made up of the following variables:
Frontal area
Coefficient of drag
Fluid density
Velocity
The frontal area represents the actual projected area that
is passing through the fluid, or in this case the horse and rider travelling
through air. Frontal area would be
increased for a jockey that stands taller because less of his body is “masked”
by the horses head and neck. Now,
the force of drag is just a number, and what really matters in racing is
power. Power represents the rate of
energy usage needed to overcome a force.
Therefore, the higher the aerodynamic force, the more energy that will
be need to be consumed to overcome it.
Horses are not machines and we need to remember that they have a finite
amount of energy. Only so much gas
in the tank, so to speak.
When converting force to power, the one variable that has
the largest influence is velocity.
This is because it does not scale linearly like the other
variables. This means that to
compensate for small increases in speed, the other variables must be reduced
significantly. Looking at the
other variables, we cannot change air density and unless we start changing the
shape of racehorses, the overall coefficient of drag will also remain constant. This only leaves frontal area. It is to the race team’s advantage to
keep the frontal area as small as possible.
But what does this mean in real numbers? If we assume a horse is running at a
constant speed of 35 mph (and neglecting any potential effect of drafting), the
horse will be outputting approximately 2050 watts (just under 3 horsepower) to
overcome the aerodynamic drag force.
Now if the jockey stands 10 inches taller at the same speed, the horse
will be outputting 2550 watts (about 3.5 horsepower). This is a 16% increase in power output just to overcome the
increase in frontal area!!
Alternatively, if the rider were to stay tucked down, the horse outputting
the same 2550 watts could theoretically travel about 37 mph.
This was very surprising to me. A horse can travel an average of 2 mph faster using the same
amount of energy only if the jockey stays tucked down rather than standing up
higher. These energy values are
small considering the largest amount of energy used by a horse is during acceleration. Sir Isaac Newton was a pretty smart guy
and according to his theories, to get a horse to accelerate for the last stretch
drive takes anywhere from 8,000 watts (11hp) to 12,000 watts (16hp) of power. This is because horses are heavy and
they are already traveling pretty fast.
Pending the responses to this article, I can run the numbers
on how much extra energy is required to carry that extra pound or 2 in a
hanidcap but I wanted to separate the scopes here.
The aerodynamic forces are only a fraction of the total
during a stretch drive, but in a game of inches, every little bit counts. So the next time you see a jockey
standing tall on a horse on the backstretch, take note and see how much kick
that horse has left at the finish.
My inner nerd would love to get a horse and jockey into a
wind tunnel, but until that day, I’ll just keep my eye on jockeys who like to
stay as crouched as they can during a race.