I really saw a difference when I had time to workout my horses recently with the revamp of the exercise code. It was really awesome to be able to see a payoff. 
But I have also noticed that when regularly raced a horse does not get the same benefit. Are the horses still getting increased fitness when raced or only in workouts? I would notice a trot/canter workout would benefit them a lot more than say an 8 furlong race…
I haven’t updated the racing fitness code, so it may need some tweaking.
However, a horse can work really really hard in a race (and still come in last) and gain a lot of fitness. Likewise, a horse can totally slack off and not gain as much. It also depends on how fit the horse is coming in to the race…a 99% fit horse isn’t necessarily going to get to 100% with a race, just maintain the 99%.
If a horse goes in to a short distance race (say five furlongs) and only gets knocked down from an “A” to a “D” in his natural energy, does that mean he might have the stamina to do a longer race?