Hi Rebecca, you can put standing wraps or stable boots, and of course cool as much as you can (clay, ice, Tendonyl gel, white water, arnica gel...). Walking him as much as you can is also important, you can give him as well some supplements that can help articulations, tendons and muscles to recover (Or joint is a good one for example) :)
I like to give liniment/ vetrolin bathes, and use green cool/blue lotion on their cannons before bandaging. Also massaging their backs/necks, and having them do stretches after work
I'd say stable boots, and as Tessy said, walk a lot! You also can try argyle, and maybe electrolytes, which is going to help your horse to get re-hydrated!
You should massage your horse's legs before and after the trainings with a gel to limit inflammation, and walk a lot before and after your trainings :)