Karin C:

A speed of 58 MPH is not supported by the data.

The AQHA website lists the ten fastest times for the quarter mile (440 yards). http://racing.aqha.com/racing/dyn_content.aspx?FQD=http://www.aqha.com/aqharacing.com/events/allamerican/fastesttimes.html

The fastest time was set by No Secrets Here in 2006, :20.886. If you do the math, that works out to 43.091 MPH.

The longer the race, the slower the final pace. The current world record for 1 mile is held by Mr. Light, 1:31.41 set at Gulfstream Park in January of 2005. http://www.bloodhorse.com/horse-racing/articles/28890/mr-light-shows-way-in-poker-handicap This works out to 39.38 MPH.

Here in America, horses don’t run races at distances of 2 miles very often, but overseas, both in the UK/Europe and in the southern hemisphere (both South America and Australia/New Zealand), the two-mile distance is the "cup" distance and top-class horses still contest races at that distance. The world record for 2 miles is held by Polazel, 3:15, http://thoroughbredchampions.com/library/worldrec.htm, set in July of 1924 over a turf course that was so hard that the horse’s hooves rattled. That works out to 36.92 MPH.

What fascinates me is that in recent years, harness horses (trotters and pacers) have been lowering the world records for the trot and the pace to the point where a lot of horses couldn’t keep up at the gallop.

The world record time for a trotter is 1:49.3, set by Enough Talk in 2008. That’s 32.94 MPH. The world record for a pacer is 1:46.4, set by Holborn Hanover in 2006. That’s 33.83 MPH. http://www.ustrotting.com/misc/world_records/recordperformers.cfm That’s awful darn fast for a horse that is doing it in "second gear"!

If you want to talk about sustained speed over a very long distance, then I don’t think you can do better than look at the 100 mile Tevis Cup competitive endurance ride. This "race" is a ride over 100 miles that re-traces the final leg of the Pony Express route through the mountains and down into Auburn, CA. The fastest time was 11 hours and 18 minutes, set by a half-Arab named Pancho in 1968. That works out to 11.3 miles per hour. However, this is elapsed time, not absolute time: Tevis Cup rules require rest stops at certain points, and the clock stops while the horse is resting and re-starts when the horse leaves the checkpoint.

It’s gotta be pointed out that in every one of these cases, the horses involved were superbly conditioned and in the peak of health, were all ridden/handled by people who were dedicated and focused on helping the horse achieve the absolute maximum speed it can. Also, in the case of the race horses, the surface they were running over was a racetrack, which is not comparable to the kinds of surfaces that pleasure horses might be ridden over.

Another caveat: at the various two-year-old in training sales for Thoroughbreds around the country, you’ll get Thoroughbreds that will exceed the world records set by Quarter Horses for distances of 220 yards (1 furlong) and a quarter mile (2 furlongs), but those records are not official times. The horses are timed from a running start, not from a starting gate, and the timing is not as precise as in a race.

Hope that helps!
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Thank you, Vicki, for posting those links. The first one is clearly in error, and I have corrected it. Given the information on the AQHA website, there is no supporting data for a speed of 58 MPH by a Quarter Horse. You can check my references and calculations if you like.

The other website had more correct information, although they are out of date on the world record for the mile. Dr. Fager no longer owns that record, although both Elusive Quality and Mr. Light, who have both broken Dr. Fager’s record, did it on the turf.

Dr. George Pratt, an MIT professor who has done extensive work on stride analysis and biomechanics of the Thoroughbred, has postulated that the absolute limit of how fast a Thoroughbred can go is in the 47-48 MPH range for a quarter of a mile. Any improvements in speed beyond that will be the result of breakthroughs in equipment or track technology.