How do you measure the stride of a horse?

Question

How do you measure the stride of a horse?

Answer 1

A stride is a complete movement from the point of one foot striking the ground, leaving it, then striking the ground again. Stride length is the distance traveled in one stride.  

Measuring stride length mechanically is easy enough:  you mark where a specified foot hits the ground, and then measure the distance to where that foot next strikes the ground.  That distance is the length of stride.

Where it gets complicated is when someone tries to calculate stride length using film footage of a horse running.  I know that years and years ago, someone tried to calculate Man O' War's length of stride based on film footage of him in one of his races (I think his final race, the Kennilworth Gold Cup against Sir Barton), and came up with a figure that would have had "Big Red" having a longer stride than any other Thoroughbred.  But right away there were problems:  without knowing the exact placement of the camera and some other factors which I can't remember, it was argued that the calculations were off and couldn't be relied on.  In theory, you can use film footage to calculate stride length as follows:  by measuring the distance on the screen between successive imprints of the same hoof (or better yet, taking the average distance between successive imprints of all four hoofs) and comparing it to a marker of known length, you can calculate stride length.  But the problem is that camera angle can cause distortions in the measurement, and in old footage where the size of the "marker of known length" is only approximate, errors are introduced.

I believe that the average stride of a Thoroughbred going at a good solid gallop is going to be around 18-21 feet.  Dr. George Pratt of MIT has done some in-depth analysis of Thoroughbred gait, and has come up with some interesting data.  Dr. Pratt has done a lot of work on stride analysis, searching for the "Holy Grail" of horse evaluation:  a way of discerning which yearlings or two-year-olds in training have the right biomechanics to become superior earners on the racetrack.  A lot of his work is proprietary, because of course if he finds the "Grail" he wants to be the beneficiary of his research-- and IMO that's as it should be.

He's gone well beyond stride length in defining what makes a superior runner;  length of stride is a part of the equation, but there are other factors that are as important or more important.  Also true:  there are factors that can change the biomechanics of a horse's stride and many other factors that influence whether a horse can be successful as a racehorse-- most notably factors relating to breathing, cardiac capacity, and muscle composition.

There are an awful lot of people who are searching for the "gold standard" in selection of unraced Thoroughbreds, that one measurement or factor or combinations of measurements that can reveal the champion in the unraced horse.  People are still searching, and judging from the number of high-priced sales yearlings and two-year-olds that never make it to the races, most people are still getting it wrong.