That was a nice time, wasn’t it? 2:26.65. Secretariat ran each quarter faster than the preceding quarter, accelerating at the finish, winning with a long lead; by the math, couldn’t have had a 1:15 first half. That jockey put on the gas during the back stretch, and just went by everyone after just keeping pace. That horse had an abnormally large heart, if memory serves.
Should watch the video of Secretariot’s acceleration from last to first in the 1st turn in the Preakness in 1973.
It did...and so did Sham who most likely would have won the '73 triple crown had it not been for Secretariat. IIRC, the original use of the term, "X factor" was for the oversize heart of a racehorse, and is believed to be a recessive trait in thoroughbreds that can lead to a healthy heart being 2X (or even more) larger than a "normal" horse heart.