My pony looses shape really quickly, she looses muscle and gains weight!
But what I do when I give her a spell is walk and a little trot for 20mins 3 days in a row,
Then a break,
Then walk trot 30mins with a little canter for about 5-7 days with a break or two in between,
Then walk trot canter and maybe a little crossbar jump, just for the hell of it. For about 4 days
Then cause she's a barrel racer, I walk trot around barrels and a little canter, working on the correct line etc,
Then by then it's hard to stop her from doing a flat chap around the joint... so after all that I then do a full canter with a faster canter home around barrels... and yeah, then she is pretty fit...
Also with the walking trotting and cantering I go up hills and over rough terrain etc. heaps of trail riding, keeps there mind occupied.
Also of course warming up properly and cooling down etc.! (: and she's 13years old (: