Which of the following is a consequence of working a horse on an arena surface that is too soft?

Working a horse on an arena surface that is too soft can lead to a significant risk to the tendons of the horse. When the footing is excessively soft, it can cause the horse to work harder to gain traction and maintain stability, which may result in the horse exerting unnatural strain on its tendons and ligaments. This increased stress can lead to injuries such as tendonitis or other soft tissue injuries, primarily because the horse’s body is not able to effectively support itself under such conditions.

In contrast, improved performance, increased cardiovascular endurance, and better joint flexibility are typically associated with optimal training conditions and appropriate surfaces that promote a horse's ability to move efficiently and safely. A soft surface does not provide the necessary support for the horse’s weight and movement, therefore it detracts from, rather than enhances, performance abilities and physical conditioning.

Focusing on maintaining a suitable surface is essential for the overall health and safety of the horse, making it crucial to avoid overly soft conditions when training.