Collection is a prerequisite for all higher dressage movements. In these pictures, German olympic dressage pair Kristina Bröring Sprehe and Desperados.
The horse at liberty carries most of his weight on the forelegs, so untrained horses carry themeselves on the forehand in an apparent downhill way of going.
Collection implies an uphill way of going. It is characterized by a highly arched neck where the poll is the highest point and the topline physique of the horse is highly developed.
The collected horse has learned to lower his hindquarters using a combination of muscles, including the abdominal and sub-lumbar muscles, which increases the engagement of the hindquarters.
So collection is a result of the physical development of particular muscles, including the dorsal (topline) muscles. The development of collection redresses the previously mentioned downhill situation, where the hindquarters now step in advance of a line dropped from the stifle and lower.
This is said to put the horse in a stronger position to engage his hindlegs while carrying a rider.
As collection develops, a quality known as ‘cadence’ also develops. The concept of cadence is derived from music, where it identifies a rhythmical motion accentuated by a pause.
The period of suspension is at its greatest during the progressive development of collection leading ultimately to passage and piaffe.
This suspension makes for a clear pause of the horse’s legs in the swing phase, which is known as cadence.
As the correctly trained dressage horse develops, the limb muscles for collection increase in tone and this is likely to have an effect of bringing the hindhooves closer to the fronthooves, where the horse now shows the more collected posture described as ‘sitting’.