We talk a lot about collection in riding, but what is collection, exactly? And how do our horses achieve it?

This almost mystical concept conjures different ideas from different riders and trainers across the globe, but new biomechanical research in Sweden is shedding light on this mystery. By studying the precise, detailed movements (the kinematics) of both horse and rider in three trotting gaits on a treadmill, researchers have gained a better understanding of exactly what’s going on during collection, and how horses and riders physically interact with each other.

Such a study could show whether riders are actually doing what they (and their instructors) think they’re doing, and could also help trainers be more precise in their explanations, said Anna Byström, a PhD candidate at the Swedish University of Agricultural Sciences’ Institute for Anatomy, Physiology, and Biochemistry, in Uppsala. It can also help define what collection actually is, she added.

Byström and colleagues analyzed the three-dimensional movements of seven high-level dressage horse/rider teams in three gaits: collected trot (in three speeds), free trot (performed on a loose-rein), and passage. The horses and riders, equipped with reflective markers, performed on a high-speed treadmill in a laboratory.

In passage, the rider’s pelvis tilted forward (“tucked in” towards the front of the saddle) and the rider’s back was more rounded than in collected trot, Byström said. In passage the researchers also noted decreased phase-shifts between horse and rider movements—in other words the rider was more “in sync&