—Jessica, via e-mail
It’s great to see these semi-retired horses finding second or third careers in their later years, and it’s wonderful you’re being so proactive in this horse’s management. I’ll break my answer into two parts—managing the front foot lameness and building condition while minimizing injury risk.
As I am sure you know, the horse’s foot is an extremely complex structure and there are a multitude of things that can cause hoof lameness. The first, and most important, step in managing the lameness will be to accurately characterize the cause. Is the gelding’s front-foot lameness due to laminitis, navicular syndrome, coffin joint osteoarthritis, a soft-tissue injury, or something else? Knowing the underlying cause will help guide an appropriate and effective management program with considerations for ideal footing, housing, shoeing and appropriate length and intensity of exercise.
Take, for example, a horse with a deep digital flexor tendon (DDFT) injury at the level of the navicular bone; this horse might benefit from a shoe and/or pad that elevates the heel region as this decreases tension on the DDFT. Alternatively, corrective shoeing for a horse with thin soles might consist of shoes with pads, particularly if the horse lives or works in an area with hard or rocky footing. Even the ideal housing condition could depend on the underlying cause of lameness. While a horse with osteoarthritis might benefit from living in pasture so he can continually move around, a horse with a history of laminitis should not be allowed access to a grassy pasture.
The second part of your question correctly identifies the fact that conditioning is always walking a fine line between building strength and fitness while not inducing injury. As discussed, the underlying cause of lameness will dictate some of the conditioning parameters.
But, more generally speaking, consider that injury is often the result of repetitive motion, so the more variety you add to the training program, the better. Just as in humans, cross-training in horses has been shown to decrease the rate of injury, so incorporating work in and out of the arena, adding hill work, and minimizing repetitive figures and exercises is advisable.
Additionally, it is fairly uncommon to injure a horse by walking, so adding long slow miles is a good foundation for almost any conditioning program.
And, finally, remember to build up work gradually by increasing the speed and duration and/or decreasing the rest periods between intervals (but not all at the same time).
I hope you enjoy many years with your new family member!