I really believe the run-up
does affect early % for sure. Look at my sample database (minimum 50 race sample for each distance) of comparing the winning horse's performance at six furlongs at these different racetracks:
Keeneland (synthetic)
Run-Up = 34 feet
1FR__2FR__3FR__EP__AP___SP___E%
57.38 56.68 54.41 57.01 56.16 55.71
51.17%
Golden Gate (synthetic)
Run-Up = 50 feet
1FR__2FR__3FR__EP__AP___SP___E%
57.28 56.74 53.39 57.00 55.80 55.19
51.65
Hollywood Park (synthetic)
Run-Up = 60 feet
1FR__2FR__3FR__EP__AP___SP___E%
57.33 56.74 53.18 57.03 55.75 55.11
51.75
Santa Anita (dirt)
Run-Up = 85 feet
1FR__2FR__3FR__EP__AP___SP___E%
60.21 57.98 53.19 59.06 57.13 56.13
52.62
It seems to me the longer the run-up, the higher the E% goes. I wish I had more tracks to do some analyzing (thanks for giving me a new project
), but this topic definitely does raise an intriguing point.