After shows always put something like a muscle calmer like sore no more or liniment on the legs
Put cooling gel on his joints after every couple classes, get ice boots, shower him down after and don't feed him too many treats during the show, that's what I do and my horse is a bit older !
Does she het lame. If so try ice boots thwy are quite pricey but they cool the horses joints down and stop them from swelling. http://www.horsehealth.co.uk/leg-hoof/leg-therapy/ice-boots This is a link to the website that has the boots ✨ hope this helped 😁👍🏼