My horse keeps falling from a canter into a trot?

A horse that repeatedly breaks from the canter into the trot is communicating one or more of several specific things about his current physical capacity, his training level, his balance on the specific track being ridden, or the quality of the rider's support through the canter. Identifying which of those factors is most responsible for the breaking in any specific horse is what allows the appropriate corrective approach to be applied rather than the generic response of simply pushing the horse back into the canter after every break and hoping that repetition eventually solves the problem. Physical fitness is the most legitimate and most frequently underestimated cause of canter breaking, particularly in young horses or horses returning to work after a layoff. The canter is the most aerobically and muscularly demanding of the three basic gaits, and a horse that lacks the cardiovascular fitness, the hindquarter strength, or the topline development to sustain it will break to trot as a natural physical response to fatigue rather than as a training evasion. The horse that breaks consistently after approximately the same number of strides, that breaks more easily later in the session when fatigue has accumulated, and that canters progressively longer as fitness develops over weeks of conditioning is a horse whose breaking is primarily physical. The correct response is patient progressive conditioning — cantering for the duration the horse can currently sustain, returning to trot before the horse breaks rather than waiting for the break, and gradually extending the canter duration as fitness develops. Balance on curved tracks is the second major cause of canter breaking. The canter on a circle demands significantly more collection and more inside hind carrying capacity than the canter on a straight line, and a horse that can canter a straight line willingly may break consistently on a circle because the lateral balance demands of the curve exceed his current collection capacity. If the horse canters better on straight lines than on circles, the breaking is balance-related. The correction is working the canter on straight lines and large gentle curves initially, progressively decreasing the circle size only as the horse develops the collection the smaller circles require. Inadequate rider support is a cause that requires honest self-assessment. A rider whose seat becomes tense and restrictive in the canter, who grips with the knees and blocks the horse's back from swinging, or who does not maintain a following leg contact that supports the horse between the strides creates the conditions for canter breaking from the rider's side. If the horse canters better with a more experienced rider, the problem is at least partly the current rider's technique rather than the horse's capacity. The training response to canter breaking should be immediate and consistent — reestablish the canter promptly with the same clear cue used for the initial departure, and maintain the supportive leg through the first few strides of the reestablished canter. A horse that breaks and is immediately put back into the canter without the rider's leg maintaining a consistent supportive presence through the first strides has not been taught that maintaining the canter is the expected response.