When should you accelerate to get in front of the cow at the fence?

The timing of the acceleration in fence work — the moment the horse drives from its rate position at the cow's hip to the position ahead of the cow's shoulder that allows the correct fence turn — is one of the most consequential decisions in the fence work run, and getting it right requires reading both the cow's pace and the geometry of the remaining fence ahead. The correct acceleration moment is early enough that the horse has time to get fully ahead of the cow before the corner of the arena, where the cow will turn on its own if the horse has not turned it first, but not so early that the horse has been ahead of the cow for so long that the cow has slowed or changed its movement before the turn happens. A practical way to think about the timing is that the horse should begin its acceleration when the remaining fence is approximately twice the distance the horse needs to cover to get ahead of the cow — enough runway to complete the pass and establish position ahead before the corner forces the turn. Accelerating too late produces a turn in the corner rather than a turn in front of the cow, which scores as the cow turning itself rather than the horse turning it. Accelerating too early gives the horse position ahead of the cow but requires the horse to then rate at the reduced speed of the cow while waiting for the cow to arrive at the turn location, which loses the momentum and energy of the turn. The best fence turns happen when the acceleration and the turn happen as a nearly continuous sequence — the horse passes the cow's shoulder, plants, and rolls back — without a significant pause between getting ahead and making the turn.