I have a 10 year-old mare who has been running barrels now for about four years. After taking your clinic in Alberta, Canada, we have improved! However, I have to do one or two small loping circles to get her to relax and collect before I can let her go, or she runs with her head in the air and past the first barrel by a stride. I am guessing that we just need a little more time for her to relax and settle before we run during competition. Suggestions?
Sounds like you have been doing your homework! Congratulations on your nice results. Often times, the horse's lack of focus when entering the arena reflects on the effectiveness of the warm-up. I would certainly give her an hour, maybe more before you race. It will take at least 25 minutes to get her muscles, tendons, and ligaments loose and warmed up, and additional time to get your minds in sync and relaxed. The time of this warm-up period depends on the horse. Some need more time and some need less. The weather, competitive conditions, stage of maturity, experience and level of training all play a factor. Just remember it "takes what it takes" and is certainly no reflection on the ability of the horse. My last horse, Seven, took up to four hours of warm-up, depending on the conditions.
Remember, a good rule of thumb in the warm-up is to invest 90% of your time just walking; approximately 5% at a jog and extended trot; 2% at the lope. Add a sprint or two into the loping portion of your warm-up to prepare your horse for the sprint to the first barrel. Depending on the horse’s attitude, you then may have to ride the horse down and help her refocus mentally. I would much rather do this in the pre-game warm-up that between the first and second barrel!
Try putting her on-task the last 5-10 minutes before you go into the arena. Lateral exercises, stretches, circles, reverse arcs, all rights, stops roll backs, 360's, transitions from walk to trot to lope and back to walk, are all excellent resources to gain mental control and confidence in your pre-game warm-up. Remember to variegate the speed of your warm-up exercises. Additionally, you may want to think about warming up in your training bridle and switching to your competition bit before your run.
I find nothing wrong with circling once to help balance a young horse, but the circle is not planned to prepare a horse for the competition. This needs to be done before your name is called. Be ready to run when you enter the arena.
Gook luck and remember that warm-up is one of the most important areas of consideration in successful, consistent competition.