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EQUINE LAMENESS

Training & Bone Quality

A basic knowledge of normal and abnormal bone responses to exercise can help trainers ensure that their horses make the necessary improvements in bone quality during training. This knowledge helps the trainer reduce the potential for bone problems, such as bucked shins and fractures.

Recent research on bone responses to exercise in young Thoroughbreds may be especially important for racehorse trainers. This information can also be used when training young or untrained mature horses for other sports which place large demands on the bones. Scientists have found that to significantly increase the thickness and density of the cortex, the bones must be loaded with fast work—that is, galloping.

Moderate intensity exercise (trotting and cantering) does not result in a significant response in most horses, particularly if the young horse was active in the pasture during its growth period. Except for weanlings and yearlings that are raised in a barn and allowed little exercise, the bones of most young adult horses can cope with the load during moderate intensity exercise—provided the other musculoskeletal structures have also adapted sufficiently. Note: It is assumed that bone quality is normal to begin with and not decreased by metabolic bone disease (discussed later), enforced inactivity, a fracture, etc.

Photo Courtesy of Quarter Week

Improving bone thickness and density takes as little as 5 or 6 strides at speed, although up to 30 strides appears to be safe in untrained young horses. Thirty strides is about 1 furlong (220 yards) at the gallop. Allowing more than about 30 strides can overload the bone and eventually

cause damage, such as bucked shins or an incomplete ("stress") fracture. It takes about 10 days for bone quality to be significantly increased in response to an exercise session. Therefore, very short bouts of fast work every 7 - 10 days is the best way to increase bone quality without causing damage.

The distance of each bout of fast work can be gradually increased by 1 - 2 furlongs (or 30 - 60 strides) every 2 - 3 weeks. In between these "fast" days, the horse's fitness must be improved with the traditional slow, distance work. This is important to ensure that the other musculoskeletal structures and the cardiovascular system also adapt well. If a racehorse must go around turns, it is important to include corners or turns in the "fast work" sessions. This ensures that the bones increase their strength and resilience in the direction of greatest load during a race.

The recommendations from this research include:

• begin galloping the horse earlier in the training program (within the first few weeks)

• limit the first few gallops to 15 - 30 strides (1/2 - 1 furlong)

• separate the "fast work" sessions by 7 - 10 days

• gradually increase the distance galloped over a period of several weeks

With this approach, the young horse can still be ready to race within the traditional 12 weeks of training, with far less risk of bone problems.

If the horse is large and growing rapidly during training, the trainer should take the horse along more slowly. These horses have relatively inferior bone quality because lengthwise bone growth is given a higher priority than increasing the bone's thickness and density. It takes longer to sufficiently increase bone quality with exercise in these horses.

There is only a small difference between the workload that improves bone quality and that which overloads the bones. Longer or more frequent sessions of fast work in the first few weeks of training do not result in more or faster bone production. There is a limit to how quickly bone can increase its strength in response to exercise. Pushing the horse too far, too soon is likely to cause injury.

Also explained in this chapter:
Bone Structure and Function, Bone Fractures,
Bone Infection (Osteomyelitis), "Big Head" Disease (Nutritional Secondary Hypoparathyroidism), Rickets, and More!

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Equine Lameness!

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