Let's say a horse gets loose on the lead and runs a final time of 1:47 at 1 1/8 mile. And let's say the pace was 1:09 4/5th. Now let's say the average or par pace time for this final time is 1:08 flat. The race comes up slow 9 at the pace call. How about a speed figure of 120. Okay.
Now let's pretend this horse comes back in 3 weeks and gets loose on the lead again and finishes at the same 1:47 but posted this final time with a par pace of 1:08 flat. This would lead you to believe that pace velocity does not matter. Final time is all that matters. In other words, pace does not influence final time. But wait. Let's try one more scenario. Three weeks after the last performance our good thing comes back and tries to get loose on the lead again as his running style requires but this time there are two challengers. At the pace call they battle it out in a 1:07 flat but our good thing wins in a photo finish at 1:47 again. That's a fast 5 at the pace call!
Now which race deserves the best speed figure?
Here's my answer. The race of 1:09 4/5th was run mostly from the aerobic system. There was plenty of oxygen and the anaerobic:aerobic ratio was low enough that the build up of lactic acid was removed efficiently. The horse never seriously approached the anaerobic threshold, sometimes called the lactate threshold; this is where at some point oxygen debt must be paid. Lollygagged to the pace call and then sprinted home. Easy 1:47. [Read more about it].
The 1:47 earned with a par pace of 1:08 called on extra reserves of energy but still not fast enough to cause serious problems. That's a nice 1:47
Okay. As I said the race came up a Fast 5! Horses faced with that kind of velocity at the pace call must call upon deep reserves of oxygen and energy in order to sustain the drive to the finish line in decent time. So the sprint to the 1:07 in our route used the anaerobic system that creates a build up of lactic acid that's greater than its removal and so the final fraction reflects the fatigue - pace fast, final fraction slow; more energy early, less energy late. Plus, since horses don't run one at a time the pace match-up and the pressure generated by the match-up can create, I believe, similar physiological effects due to stress and adrenalin. That's another post about this controversial subject for later.So, my hypothetical horse with the Fast 5 pace gets the best speed figure. That 1:47 was a tough one to earn and the resulting speed figure should reflect that reality. Give me a 120 speed figure against a par pace and I'm a believer. Adjusting for pace velocity adds the physiological effects of racing to the mix when final time figures are calculated. How was that figure earned? That's an important question to me.