It is all about having a good recovery. Meaning that you can't suddenly stop a horse after a training session. You need to provide leg and back care. For example, thalassotherapy or simply cold shower on the legs, because the body temperature can be really high after training. The goal is for the horse to get his normal temperature back quickly.
In our facilities we have the chance to be able to walk the horses in a river to cool down the legs.
And for my top horses, they regularly have massages in thalassotherapy.