How do collection and extension differ in horse training?

In horsemanship, collection and extension represent opposite approaches to a horse's movement and posture.

Collection is characterized by controlled, precise, and elevated movement. In this state, the horse’s balance is shifted rearward, which lightens the forehand and increases agility in confined spaces. The horse carries its head and neck higher, and its gaits are shortened and raised. This training aims to improve the horse's bearing and ensure it can support the rider's weight without placing undue strain on its joints or muscles.123

Extension is the opposite of collection, defined by smooth, swift, and reaching movement. During an extended gait, the horse is permitted to stretch its neck forward, shifting more of its weight onto its forequarters. While collection focuses on compactness and upward carriage, extension emphasizes forward reach and ground-covering strides.13

Both elements are fundamental to dressage, where horses are trained to transition between these states with balance, suppleness, and obedience.2