What is a lead and why does it matter which lead a horse is on?

A lead refers to which front and hind leg pair is reaching furthest forward during the canter or lope — when a horse is on the left lead, the left front and left hind are the leading legs, and the footfall sequence begins on the right hind. On the right lead, the opposite is true. The lead matters for both balance and correctness. A horse traveling on the correct lead for the direction of travel is balanced through turns and circles. On the left lead traveling left, the horse's natural body lean and weight distribution support the turn. On the wrong lead — the left lead while traveling right, called a counter-canter when deliberate or a wrong lead when accidental — the horse's balance is working against the turn, which creates mechanical disadvantage and can stress the horse's joints. Clinton Anderson teaches that recognizing which lead a horse is on is a foundational rider skill, and that riders who cannot feel or see the lead cannot correct a wrong departure or communicate clearly about lead changes. The feel of the correct lead — the horse feeling like it is reaching forward on the side toward which you are traveling — is learnable with practice and is essential for any work at the canter or lope. At the competition level, lead correctness is judged in every western and English discipline that includes canter or lope work. Departing on the wrong lead, failing to change leads when direction changes, or cross-cantering are faults penalized across all disciplines from ranch riding to dressage to hunt seat equitation. Understanding leads and lead changes is therefore not optional knowledge for any serious rider.