The canter is 3-beat gait followed by a suspension phase when all four feet are off the ground. The canter can be "true"; leading with the left leg when going to the left or "counter"; leading with the left leg (and staying flexed towards the left leg) when cantering to the right.
It can also be said to be ""disunited" when the correct sequence of leg movement is broken i.e. a horse changes legs in front but does not change behind.
For a left lead canter the sequence runs:
Right hind supports all weight, all other feet clear of the ground
Weight shared by right hind, left hind and right fore, left fore clear of the ground
Weight shared by left hind and right fore as left fore touches the ground and right hind lifts
Weight shared by both fore and left hind as right hind lifts
"The correct activity of the back produces a swinging movement and becomes evident to the rider by a swinging back and resilient chewing on the bit. A swinging back must therefore be one of the trainer's main goals during the entire course of training." (Paul Plinzner in a footnote to Gustav Steinbrecht's "Gymnasium of the Horse" )
