What is tempo in dressage and how does it differ from rhythm?

Tempo and rhythm are related but distinct concepts in dressage, and confusing them produces training errors that appear to address one quality while actually working on the other. Rhythm describes the pattern of footfalls in each gait — the four-beat walk, the two-beat trot with suspension, the three-beat canter with suspension — and whether this pattern is regular and correct. Tempo describes the rate at which the rhythmic pattern repeats — how many footfalls per minute, or equivalently how fast or slow the horse is moving within its gait. A horse can have correct rhythm at any tempo: a collected trot with short, active steps that repeat quickly has a higher tempo than an extended trot with long, ground-covering strides that repeat more slowly, but both should show the same correct two-beat diagonal pattern if the rhythm is maintained. Problems arise when rhythm and tempo are confused — when a horse is asked to go slower and slows its rhythm to a lethargic, irregular pattern rather than maintaining the same regular two-beat trot at a lower tempo; or when a horse is pushed faster and begins to run rather than maintaining the same regular rhythm at a higher tempo with longer strides. The ability to adjust tempo — making the horse's pace within any gait faster or slower — without losing the regularity of the rhythm is a significant training skill that tests the horse's response to the half-halt and its ability to maintain energy without rushing. Competition dressage judges evaluate both rhythm and tempo: they assess the regularity of the footfall pattern as part of their basic gait assessment, and they evaluate whether tempo is appropriate for the level and size of the arena, with a tempo that is too quick or too slow for the movement being performed affecting the score even when the rhythm itself is regular.