The handicapping system will help them too. Horses that have had an extended absence tend to be allowed 7-10lbs for it.
(If I were a trainer with a long-term plan for a horse that's the route I would take rather than keep running it down the park. I think horses that get into the habit of running publicly well below their best find it hard to get out of the habit, whereas a horse that's been kept active and interested in life away from the track might be literally champing at the bit for some action. Which would appeal to your sex-drive more, constantly banging away at an old bike or waiting for Victoria Coren to give you the come-on?)