On lengthening a horse’s natural stride – what’s realistic? An equine expert weighs in.

A rider with a smaller horse asks “Can you really lengthen a horse’s natural stride?”
 According to Dr. Hilary Clayton, the leading equine expert in equine gait biomechanics and Sport Horse science … to an extent, yes.

Some excerpts from the author’s article:
 I rejected one horse trainer’s recommendation to inject everything from my horse’s coffin joints to her hocks and stifles (to which my vet laughed and rolled her eyes) in order to get a couple more inches out of her canter. …

Dr Clayton explained to me that at the trot and canter, the suspension phase of the stride contributes largely to stride length. “As the propulsive muscles get stronger, the horse is able to push off into a higher suspension and will then cover more ground while in the air,” she said. “An important point is that increasing the suspension requires more upward propulsion; just driving the horse forward is not effective. So ride the horse round and with an upward feel–not long and flat–to increase stride length.”

https://thehorse.com/136036/for-want-of-a-12-foot-stride/