what is a stretch of grass called which racehorses are exercised.

Question
 

Answer
Hi Mark,
      Race horses are usually trained on a race course or race track. There are many different surfaces to the training tracks, sand, woodchips, sawdust, grass, dirt and no doubt some others I dont know about.
In New Zealand and Australia many horses are trained and exercised on a beach. The sand is softer on the horses legs and joints and the sea water is really good for them.
I hope this helps,
Don