What to do if the horse hesitates and is nervous about cantering under saddle?

A horse that hesitates, tenses, or shows anxiety about cantering under saddle is communicating something important, and the worst response is to simply apply more leg, more crop, or more pressure to force the canter through the resistance. That approach addresses the symptom by overpowering it rather than addressing the cause, and a horse pushed through canter anxiety without the underlying reason being resolved becomes progressively more anxious about the gait. Physical evaluation is the first obligation. A horse that was previously willing to canter and has become reluctant is almost certainly experiencing something physical — back soreness, hock pain, sacroiliac dysfunction, kissing spine, or a poorly fitted saddle that creates acute pressure when the horse rounds his back in the canter transition. Have your veterinarian evaluate the horse specifically with the canter reluctance in mind, and have a saddle fitter evaluate the fit during movement before concluding the issue is purely behavioral. Assuming the horse is physically sound, rebuild confidence by identifying the earliest point in the sequence where the anxiety appears and working systematically from there rather than pushing through to the canter itself. For many horses the anxiety begins to build before the canter is asked — during the trot that precedes the departure, when the rider's position changes in preparation. Keeping the horse relaxed and forward in the trot near that point without asking for the canter until the anxiety reduces builds the calm foundation from which the canter can be reintroduced. Longeing the horse into the canter before riding it is one of the most practical tools. A horse that canters willingly on the longe but hesitates under saddle has told you that the gait itself is not the problem — the rider's presence or aids during the canter is what produces the anxiety. Longe the horse into relaxed willing canter on both leads before each riding session during retraining. The rider's own anxiety is a factor that cannot be ignored. A rider who is bracing, holding breath, or gripping with the knees in anticipation of the horse's reluctance communicates that anticipatory tension to the horse before any visible resistance has occurred. Riding the transition with a deliberately relaxed seat and the same quiet confidence with which you would ask for a trot transition communicates that this is an unremarkable comfortable request.