Why a partial massage?
It is not a good idea to do a full body massage and work out all the soreness of the muscles if your just going to go straight back to riding/competing. That is where the partial massage comes in.
Targeting the main points for soreness in a horse will help alleviate some pain to better help them in a pinch right before competing. Targeting the head/poll, front and back tendons, cinch area, back, and some quick stretching. Consider this a great warm up for your horse before you jump right into the arena!