Collection occurs when a
horse carries more weight on the
hind legs than the
front legs. The horse draws its body together so that it becomes like a giant
spring whose stored
energy can be reclaimed for fighting or running from a predator. The largest organic spring in the horse's body, and therefore the easiest one to observe in action, is the
back, including the
spine and the associated
musculature that draws it together in much the same way that a
bow is drawn by an
archer.