A lot of time I see people decide that a 3-year-old horse is talented for dressage and that how they work this horse from the very beginning. I don't agree with that. Even an advanced dressage horse benefits from occasional hacking and gymnastic jumping. For a young horse it should be mandatory. Realize how much more fun it is for your young horse not to have two same days. Riding a green horse 4 times a week is quite enough. You can either take one of those 4 days and work your horse on the lunge or have an extra 5th day for it. And other 4 days can be: 1.flat work in arena, 2.hacking or trail riding, 3.going over small obstacles or cavalletty and the 4th day can be a flat work in the arena again. This is only an example. You can lunge your horse prior riding and do not set a whole session for it. You can work a little bit in arena and then go on a trail ride. You can havve a session of free jumping. There is no hard rules.

Hacking is excellent to build muscles and endurance without worrying about the frame and going on the bit. Just riding up and down hills will work wonders to your horse's haunches and back muscles. Teaching your youngster to listen to you on a trail ride has a benefit of logic in it. There is usually a reason why you want something from your horse on a trail ride in comparison to riding in arena. Young horses are not mentally ready to focus and obey without questions as schooled horses do. They ask a lot of them in arena, because they do not understand why they have to do something. Trail ride can prepare them mentally as much as physically for their future discipline. Same benefits derived from going over obstacles. They do not have to be high enough to induce jumping, but they can be a variety of things to navigate through, trot over, etc. They give your youngster a job to do the same way trail riding does. Both these types of work will create a feeling of trust and team work between you and your horse and physical development too.

Of course you must take time and work progressively. Go trail riding only after you developed some basic obedience from your horse and go with an experienced rider and a horse. Do not try anything that brings fear and uncertainty out. You will only make things worse. At first walk your horse in hand over obstacles to give her confidence. Introduce new obstacles gradually, one at a time. Always stay calm, with clear head and be very sympathetic to your horse's reactions and emotions.

There is a wonderful book on this subject - Reiner Klimke's The Basic Training of a Young Horse.

Happy riding...