3 Rules to Maximize Time Off - Periods of downtime come as realistic parts of horse ownership, although how a rider uses these stretches of poor weather or busy schedules contributes profoundly to a horse’s long-term soundness and performance. Recent data from biomechanics researchers and veterinary schools shows that large vacillations in fitness can be detrimental to overall health, particularly for horses past their mid-teen years. Most notably, periods of lesser activity lasting over a month can weaken deep postural muscles and supporting soft tissue.