Horses Back

["guest@endurance.net" <guest@endurance.net>]

Ann Branch Bubblegumlady@aol.com
I have a 6year old that has never done anything. I have been working him slow on hills and teaching him to put his head down.when he gets excited up goes the head, back hollows and he gets a sore back.I have been working on him the last 6 months.We are making slow progress. How long do most horses with week backs take to get stong enough for endurance riding? and what exercise help the most? 
                           Getting Frustrated