 This practice often results in a horse that is working in a "headset" or "outline" that, to the inexperienced observer appears acceptable, but the horse has no self-carriage or suppleness and does not properly engage its hindquarters.These pieces of equipment can have very detrimental effects if they are adjusted tightly, used strongly, or if used for long periods of time.Horses may become hard-mouthed and heavy, and they will begin to travel on the forehand if the rider can not keep sufficient impulsion.