Which trait is undesirable in horse movement?

Stiffness in horse movement is considered undesirable because it can indicate a lack of flexibility and smoothness in the horse's gait. When a horse moves stiffly, it often demonstrates restricted joint movement and poor overall balance, impacting its ability to perform effectively in various disciplines. Stiffness can lead to a higher risk of injuries, as the horse is unable to absorb impact and maintain fluid motion.

In contrast, traits like straightness, elegance, and rhythm are associated with desirable movement qualities. Straightness indicates proper alignment, which is crucial for balance and efficient movement. Elegance reflects a horse's graceful and attractive way of moving, enhancing its overall appearance and appeal in competitive settings. Rhythm pertains to the horse’s ability to maintain a consistent beat in its gaits, which is essential for performance and is often indicative of good training and conditioning. Thus, stiffness stands out as a negative trait that compromises the horse's movement quality.