When Can I Ride my New OTTB?

I just wanted to let you know what we have been doing lately. Votive has settled in extremely well here in Vermont. She goes outside in the round pen for a couple of hours every day, she doesn’t like bugs so we don’t push it on time outside. Yesterday, she had her new shoes put on and was very well behaved as the farrier even commented how well she did.  I have focused our energy on getting to know each other and for Votive to know she can trust my actions. So far a day hasn’t gone by that I haven’t done a little something with her, even if it is a walk outside to munch on the grass. We have been doing a lot of ground work and familiarizing her with the indoor ring. We walk and trot while others are in there with lessons and riding. I put her on the lunge line for the first time yesterday and she was great. She needed a little persuasion to keep moving. We only did a walk to start, but the other horses were trotting and cantering and Votive stayed calm and did as I asked. We will be doing the same tonight with all her tack on again. I can’t wait to actually ride her as I feel the transition will go well.
A few questions: How long should I wait until I do get on? Is there any trick I need to know for the first time riding? One person had told me I can’t sit completely in the saddle at first since they are not use to the weight on their backs, is that true?

Elizabeth’s Training Note:
You can ride your horse as soon as it has recovered from the trip to its new home unless the horse has an injury. Horses at the track are used to being ridden everyday and they are more stressed by turnout alone than they would be by your riding the horse. It is a always a good idea to have a chiropractor look at your horse to see if anything is out of alignment. The quicker you get your horse adjusted the quicker he will settle into his new routine. If your horse is sore and you turn him out for six months, he may compensate for the injury and cause more alignment problems and muscles may develop incorrectly. Better to get everything aligned and start lunging and riding to hold the alignment and start building sport horse muscle.