What made Secretariat so fast?

Was it having a long stride ange that crossed the ground faster than other horses? I know his stride angle was around 105 degrees while Man O’ War’s was 88 degrees. But Man O’ War had a longer bound so Secretariat didn’t “float” as much. Also, Secretariat had strange proportions; like he had an unusually long body for a horse.

Any scientific info dealing with this stuff?

Secretariat’s speed and stamina were most likely due to his heart. From Wikipedia:

“This huge engine” about sums it up. It was if Secretariat was powered by a big V-8, while his opponents had little four-cylinder engines that just couldn’t keep up.

But it wasn’t just speed; it was stamina too. Thanks to his huge heart, Secretariat had energy and power to spare when closing on the finish, while other horses were spent just trying to keep up. Recall that he won the Belmont by 31 lengths, and he was going away at the time; all after racing one-and-a-half miles.

In short, it wasn’t his stride or his conformation. It was his heart.

Well that makes sense, considering his winning margins always started towards the final stretch. At the finish line he looks like he’s still accelerating while the horses far behind all look tired. Thanks.

Interestingly, Secretariat was only able to pass the large-heart gene down through his daughters.

More than you’d ever want to know about this:

In the KY Derby, recall that Secretariat ran each quarter-mile segment faster than the one before it. The successive quarter-mile times were 25-1⁄5, 24, 23-4⁄5, 23-2⁄5, and 23. This means he was still accelerating as of the final quarter-mile of the race.

An interesting article, about the X-Factor. Lots of info there. I mostly skimmed it. Thanks.