Glossary
Spinal kinematics.
Direct answer
Spinal kinematics describes how the horse's back moves in space and time: flexion and extension, lateral bending and axial rotation. Movement is captured with skin markers, optical motion capture or sensors. Forces are not part of it: forces belong to kinetics, which is a separate description.
The main source of error is skin sliding over the spinous processes. Markers sit on mobile tissue, so part of the measured movement does not come from bone at all. A second point concerns expectation: the true range of the thoracic and lumbar vertebrae is much smaller than the visible movement of the back suggests.
The difference from people is structural. The human spine is a vertical axis loaded in compression, whereas the horse's back works as a horizontal structure spanning fore and hind limbs, additionally loaded from above when ridden. Terms and values therefore do not transfer directly from one species to the other.
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