History of Racing

The Arabian racehorse originates directly from the Thoroughbred (TB) foundation sires of all light or hot-blooded horses. In the seventeenth century, these TB sires—the Darley Arabian, Godolphin Barb, and Byerly Turk—were imported to England and bred to the Queen’s mares. The Arabian was used originally as a war horse, and although the true beginnings of the Arabian horse are under a shroud of mystery and legend, the consensus is that the Middle Eastern desert Bedouin tribes played a large role in the breeding and early development of the breed.

Throughout the Middle East and Europe, Arabian racing and performance are more deeply rooted than in North America. The popularity of Arabian racing has grown enormously in the United Kingdom in the last 15 to 20 years, with a growing number of professional trainers and jockeys and a progressive increase in prize money, in part because of the high Middle Eastern sponsorship. Arabian racing in North America and around the globe is less popular, and the number of races is fewer and the amount of prize money is less compared with TB, Standardbred, and Quarter Horse racing.

The Arabian Horse Registry of America, founded in 1908, includes many types and uses. Known for stamina, speed, and elegance, Arabian horses often were bred and raised for showing in halter and performance classes. In the latter part of the twentieth century, Arabian horse popularity and breeding selection shifted to criteria based more on aesthetics than athleticism.

The Arabian racehorse lineage reflects more athleticism than is found in Arabian show horses. Consistent winners often are more heavily muscled and have stronger hindquarters with a more sloping croup and a lower head and neck carriage than a typical Arabian show horse. Recent influx of new breeding lines has given rise to concern and controversy over the purity of the lineage and the possible infusion of impure Arabian blood. Certain new stallions appear to be much taller and longer, with a body type similar to the modern day TB racehorse. Constant vigilance and careful documentation of lineage is required to preserve the pure Arabian racehorse breed.

Arabian racehorses race on the same surfaces as TB racehorses. In North America selected meets are held from California to Delaware, from Florida to Michigan, in Colorado, Texas, and Washington, and at a few other tracks. Arabian racehorses perform in fair meets, allowance races, claiming races, and futurity nominated stakes races. Racing Arabian horses also compete in the United Kingdom, Poland, France, Russia, and South America and in many Middle Eastern countries. In North America, racing begins on March 1 of the 3-year-old year. Race distances are similar to those for TB races, but the length and configuration of the racecourses vary. Shorter sprint distances, to 6 furlongs, often are run on the small tracks, whereas the longest race (2 miles [3.2 km]) is usually run on a large track. Typically, races are furlongs to miles (881 m to 2.8 km). In the United Arab Emirates (UAE) races are 5 to 12 furlongs (1 km to 2.4 km), and horses race on both dirt and turf. A sound Arabian racehorse may compete as often as every 7 to 10 days, but most are given 2 weeks between races. Because relatively few Arabians are raced, lack of entries may mandate racing whenever enough horses are entered to meet race conditions rather than when trainers and owners prefer. Racing in the United Kingdom starts in late April. Until 2001, horses did not race until 4 years of age, but in 2001 a restricted number of races for horses 3 years of age were introduced. These are high-value races and also attract horses trained in France and other European countries. Races range from 5 furlongs to 3 miles (1 km to 4.8 km). In the UAE, Arabian races average 9.5 runners.

In 1999 the International Federation of Arabian Horse Racing Authorities (IFAHR) was formed for the purpose of cooperation among all national and international Arabian horse racing associations throughout the world. The IFAHR is registered in France. Founding member countries were France, Germany, Belgium, the UAE, Qatar, Switzerland, the United Kingdom, Austria, Holland, Russia, Saudi Arabia, the United States, Turkey, Egypt, Spain, Sweden, Morocco, and Poland. In the UAE, Arabian horseracing has taken place for over two decades. Abu Dhabi, where Arabian horse racing takes place almost every week during the racing season from November to March, is the largest of the seven emirates and has also become the leader in international sponsorship of Arabian racing since 1996, supporting major races in countries such as England, the United States, France, Russia, Holland, and Belgium. The Gulf State of Qatar is also an important sponsor of international Arabian racing. Several UAE breeders maintain operations throughout Europe and the United States and are a constant force at international auctions, where stock is acquired to race in their domestic market and eventually to support breeding programs. The majority of Arabians racing in the UAE are from North American and French bloodlines. Breeding of purebred Arabian racehorses is now very popular; over 60% of the Arabian racehorses competing in the UAE today are bred in the UAE.

Ten most Common Racing-Related Lameness Conditions in the Middle East Arabian Racehorse

Ten most Common Racing-Related Lameness Conditions in the North American Arabian Racehorse

Metacarpophalangeal Joint Lameness and Carpal Osteochondral Fragmentation

In North America, osteochondral fragmentation or chip fractures of the carpal and metacarpophalangeal joints occur in Arabian racehorses but less frequently than in TBs and Quarter Horses. Smaller body size, a more gradual training regimen, and older age of horses racing likely account for the difference in incidence. However, in Middle East Arabian racehorses, lameness associated with the metacarpophalangeal joint is the most common problem encountered; carpal pain associated with osteochondral fragmentation is unusual. Early signs of arthrosis without chip fracture resolve quickly, with minor interruption in race training. The diagnosis of fetlock or carpal osteochondral fragments is straightforward. Arthroscopic surgery to remove osteochondral fragments is well accepted and successful. The prognosis depends on location, size, duration, previous treatment, and amount of associated cartilage damage. Horses with acute osteochondral fragments with only mild cartilage damage have a good prognosis. The decision for surgery often is based on economic factors.

Proliferative synovitis (villonodular synovitis) and associated fragmentation of the dorsal proximal aspect of the proximal phalanx occurs in the young Arabian racehorse. Horses have characteristic signs of effusion and a noticeable dorsal swelling. Dorsal swelling can be insidious and go unrecognized early in the disease process. Plain radiographs often reveal soft tissue swelling on the dorsal distal aspect of the third metacarpal bone (McIII) and osteochondral fragments of the proximal phalanx. Radiolucent changes in the McIII are seen in horses with severe proliferation. Ultrasonographic examination usually reveals enlargement of the dorsal synovial pad. One of us (MCR) recommends arthroscopic evaluation, removal of osteochondral fragments, and debridement of the synovial pad with a 5.2- or 3.4-mm suction punch (Dyonics, Andover, Massachusetts, United States).

In older Arabian racehorses, chronic osteoarthritis (OA) of the metacarpophalangeal joint is recognized. The trainer complains of poor performance or racing below previous levels. The metacarpophalangeal joint is enlarged from effusion or fibrosis and is warm. Horses usually respond positively to lower limb or fetlock flexion tests. Comprehensive radiographic examination should be performed. Radiological evidence of OA, such as marginal osteophytes of the proximal sesamoid bones (PSBs) and joint space narrowing, enthesophytes at capsular attachments, and soft tissue thickening, often is seen. OA of the metacarpophalangeal joint is seen frequently without osteochondral fragments and appears to be related to chronic wear and tear. In some horses OA can be managed by judicious use of intraarticular medication, but the prognosis for return to previous racing levels is guarded. In Middle East Arabian racehorses OA of the metacarpophalangeal joint and associated lameness are a major problem. Clinical signs include fetlock effusion, a positive response to lower limb and fetlock flexion tests, and a positive response to intraarticular analgesia and medication. Horses have typical radiological changes. The prognosis for continued racing is generally good, but numerous intraarticular injections of hyaluronan and corticosteroids are often needed to maintain adequate clinical comfort. Subchondral bone pain is suspected to be a factor in horses with few radiological changes or in those with increased radiopacity of the distal aspect of the McIII.

Superficial Digital Flexor Tendonitis

Superficial digital flexor (SDF) tendonitis (bowed tendon) is common and occurs from a combination of training overload and fatigue. Faulty forelimb conformation appears to be a factor, and the heavier Arabian racehorses from French bloodlines are more prone to injury of the superficial digital flexor tendon (SDFT) than those of North American origin. Lesions are found in the body and/or in the medial and lateral margins of the SDFT.

Occasionally horses run uphill at the end of a race, and SDF tendonitis occurs commonly under this condition. Sudden changes in track surfaces or training conditions are associated with an increased incidence of tendonitis. Injuries are often cumulative, and an initial injury that is overlooked or badly managed develops into a severe, career-threatening injury. Severe SDF tendonitis usually is recognized by the trainer because swelling, heat, and pain are present during palpation. More subtle swelling and pain are detected during careful palpation by a veterinarian. Thorough ultrasonographic examination is imperative to confirm the diagnosis. Careful assessment requires proper horse preparation, sedation, clipping and cleaning of the leg, and use of a high-quality ultrasound machine and a 7.5- to 10-MHz (or greater) linear transducer. Cross-sectional area (CSA) of the tendon and lesion, fiber alignment, and echogenicity of the lesion are evaluated, and any associated pathological conditions such as palmar annular ligament constriction, carpal tenosynovitis, or other soft tissue damage are assessed. Swelling is often mild if horses have been given local and systemic antiinflammatory therapy and rest. A slight increase in CSA measurement may be the only indication of SDF tendonitis, and comparison with the contralateral SDFT is mandatory. Initial management includes rest, local ice and bandage application, and administration of systemic nonsteroidal antiinflammatory drugs (NSAIDs). Horses with mild or moderate SDF tendonitis often are sent to a layup or rehabilitation farm for 3 to 6 months, where a monitoring and controlled exercise program should be initiated. Follow-up examinations are performed at 2-month intervals to determine quality of the healing and the appropriate time to return the horse to race training. A slow return to training includes progressive walking, jogging, cantering, speed work (breeze), and then racing. Time span and progression depend on maintaining an acceptable ultrasonographic appearance during each incremental increase in stress or exercise level. Tendon splitting and desmotomy of the accessory ligament of the SDFT used separately or concomitantly are successful in horses with moderate or severe tendonitis. Intralesional injections of β-aminopropionitrile fumarate (Bapten; no longer commercially available) have been used successfully. More recently, intralesional injection of autologous stem cells derived from either bone marrow or fat and platelet-rich plasma (PRP) have been used with success. One of us (AD) has successfully used intralesional injection of the porcine urinary bladder matrix product A-Cell (A Cell Vet, Columbia, MD, United States) for Arabian racehorses with SDF tendonitis and suspensory desmitis.

Prognosis varies with the severity of the injury and the stage of racing when the injury occurred. Because many Arabian horses race as older horses, even stallions and mares, providing up to a year or more of rest is not uncommon, assuming the lesion heals, before returning the horse to race training. Horses with substantial SDF tendonitis often reinjure the same area of the tendon, develop a new injury of the previously damaged tendon, or develop tendonitis of the contralateral SDFT. SDF tendonitis does occur in the hindlimb, but less often than forelimb injury, and Arabian racehorses with hindlimb SDF tendonitis have a better prognosis than those with forelimb injuries.

Suspensory Desmitis

Forelimb suspensory desmitis is an intermittent problem of many Arabian racehorses early in training. Suspensory desmitis is not considered to be as debilitating or career limiting as it is for TB racehorses. A trainer often complains that the horse is sore, but overt lameness is not present. The differential diagnosis includes bucked shins, SDF tendonitis, and metacarpophalangeal joint and carpal joint lameness. Careful palpation reveals pain and enlargement of the suspensory ligament. Although ultrasonographic examination should be performed to confirm and grade desmitis, a pattern of subtle inflammation and soreness often precedes lesions detectable by ultrasonography. Scintigraphy may be useful but is seldom recommended. Suspensory desmitis is not severe, and most often the finding of body soreness in response to increased training intensity is the only apparent clinical sign. Traumatic disruption of the suspensory apparatus is rare. Horses with suspensory desmitis usually are kept at the track because they do not require or benefit from extensive time off. We recommend 1 to 2 weeks of rest or simply a decrease in training intensity to allow for tissue adaptation. The prognosis for horses with suspensory desmitis is good if the condition is recognized early and horses are given a period of much-reduced work intensity and slow rehabilitation.

Proximal suspensory desmitis (PSD) is a clinically significant and often underdiagnosed cause of lameness in Arabian racehorses in the Middle East. One of us (AD) feels strongly that PSD and related injuries, such as avulsion fracture at the origin of the suspensory ligament on the McIII, are some of the most underrecognized sources of pain causing lameness in the Arabian racehorse. Pain associated with forelimb PSD and associated injuries can be abolished by performing lateral palmar analgesia at the level of the distal aspect of the accessory carpal bone after first performing low palmar (low four-point) analgesia. Infiltration of local anesthetic solution at the proximal aspect of the suspensory ligament can be used, but the combined carpometacarpal and middle carpal joints may be inadvertently desensitized; however, in Middle East Arabian racehorses these articular structures are rarely a source of pain. Once one forelimb is blocked, the horse often demonstrates contralateral forelimb lameness because PSD is often bilateral. Although changes associated with PSD can be identified ultrasonographically, often in Arabian racehorses ultrasonographic evidence of PSD is mild, but scintigraphically, focal areas of increased radiopharmaceutical uptake (IRU) of the proximal palmar aspect of the McIII are found, a finding that corroborates that bone injury is present. Although a diagnosis of PSD is often made in these horses, early stress fracture of the McIII may more appropriately describe this clinical syndrome, because in most horses PSD exists without concomitant McIII injury (Editors).

Treatment of Arabian racehorses with PSD and associated injuries includes an immediate removal from training, rest, and a controlled exercise program. Intralesional therapy with PRP and A-Cell and extracorporeal shock wave therapy have been used with some success. Generally, a good prognosis for return to athletic function is given. Avulsion fracture of the McIII at the suspensory ligament origin occurs less commonly and may cause sudden, severe lameness during exercise.

Proximal suspensory ligament injuries of the hindlimbs are less common than those involving the forelimbs and are more difficult to diagnose, but they are an important cause of pain causing lameness; they should be considered when investigating hindlimb lameness and carefully differentiated from distal hock joint pain.

Tarsocrural Osteochondrosis and Distal Hock Joint Pain

Tarsocrural osteochondrosis is an occasional cause of hindlimb lameness. If bog spavin is recognized when the horse is a weanling or yearling, arthroscopic surgical removal of osteochondritis dissecans (OCD) fragments usually is performed then. However, horses may arrive at the racetrack or training stable with mild tarsocrural effusion. Moderate tarsocrural effusion is commonly observed in many Middle East Arabian racehorses without evidence of osteochondrosis. Although horses are usually not lame, trainers request that the joints be drained and injected with hyaluronan and corticosteroids. If lameness is observed, if a horse has a positive response to upper limb flexion, or if moderate effusion is persistent, then radiographs should be obtained. If OCD fragments are found, we recommend arthroscopic surgery and a short (2- to 3-month) period of rest before training resumes.

Distal hock joint pain occurs in the Arabian racehorse and is seen most commonly after changes in track surfaces. These horses often do not push off or propel themselves well behind, may refuse to grab the bit or bow the neck, and use the front end to pull ahead, a gait that may lead to secondary forelimb lameness. Clinical signs often are lacking, and an upper limb flexion test may be only mildly positive. Radiological findings are often negative, but scintigraphic examination reveals IRU in the distal hock bones. OA of the centrodistal and tarsometatarsal joints is common in Middle East Arabian racehorses, and distal hock joint pain is the most common cause of hindlimb lameness. Intraarticular injection of corticosteroids produces a good response, and repeated injection is not deleterious to the future function of the hock (AD). Recently, adjunctive use of tiludronate has proved beneficial. Distal hock joint pain should be differentiated from pain originating from PSD.

Lameness of the Foot

Although Arabian horses are alleged to have solid foot structure, they do get sore feet. Long-toe, low-heel conformation is not common. Arabian horses are protected from some of the lameness conditions of the feet simply because of small body size and weight. Sore feet develop after a fast workout or race on a hard, packed racetrack. Trainers often recognize signs, and the condition is managed using ice baths, NSAIDs, and 3 to 4 days of rest.

In the Middle East, lameness attributable to the distal interphalangeal (DIP) joint is characterized by effusion, a positive response to intraarticular analgesia, and a positive response to medication with hyaluronan and corticosteroids. The DIP joint is a relatively common source of pain causing lameness in the Middle East Arabian racehorse. Although marked radiological changes may not be apparent, a response to intraarticular therapy can be dramatic, but injections may have to be repeated to maintain comfort. Less commonly, in older Arabian racehorses, “navicular syndrome” is diagnosed as the cause of foot lameness. Horses may improve for a short time with intraarticular injections into the DIP joint. In horses with pain originating from the navicular bone without concomitant deep digital flexor tendonitis tiludronate is given adjunctively. Other common causes of foot-related lameness are abscesses, bruised heels and quarters, and poor foot balance.

Myopathy

In the Middle East one of us (AD) has managed many Arabian racehorses, especially those from certain bloodlines, with recurrent exertional rhabdomyolysis (RER). This condition can manifest as acute “tying-up”(usually following a change in management such as a return to training after a period of rest) or as a cause of poor performance in horses with subclinical, chronic elevations in the serum muscle enzyme concentrations of creatine kinase (CK) and aspartate transaminase (AST). RER appears to be caused by an inherited, intermittent, stress-induced defect in regulation of muscle contraction (see Chapter 83). RER can be successfully managed with exercise and dietary changes. Starch in the diet is replaced by rice bran (which can be fed in specialized feeds). Ensuring that the horse has regular exercise including short periods of fast exercise is an essential component of the management of horses with RER. Acute RER invariably occurs during periods of submaximal exercise. The condition is monitored by regularly following blood CK and AST levels. CK is quickly excreted through the kidney, and therefore a chronic elevation in serum levels of CK is indicative of ongoing muscle damage. Because AST is metabolized in the liver, serum levels are slower to rise and fall during acute, initial muscle damage.

Stifle and Carpal Lameness

In North America the most common source of hindlimb soreness is the stifle region. In the Middle East Arabian racehorse, stifle region pain is uncommon, as is lameness associated with the carpus, and these conditions are grouped together. Early in training a horse may become sore and stiff, usually bilaterally. Intermittent upward fixation of the patella is common as in other young sports horses. Stifle soreness is common in young horses shod with flat shoes and training on a soft track. Soft tissues around the stifle become inflamed. Clinical signs include a shortened stride and an unwillingness to extend the stride behind, or actual upward fixation of the patella, with characteristic stifle and hock extension and toe drag. With early detection, horses with stifle region lameness are assumed to have a soft tissue problem and are managed by decreasing training intensity and the administration of NSAIDs. Occasionally an internal blister is injected around the patellar ligaments, especially if evidence of upward fixation of the patella exists. If effusion of the femoropatellar joint accompanies the upward fixation of the patella, radiographs should be obtained. Results are usually negative, but some horses have underlying OCD of the lateral trochlear ridge of the femur. Surgical debridement is recommended, especially if a flaplike lesion exists. OCD lesions usually are detected early in race training if they are clinically important. In Middle East Arabian racehorses the most common source of stifle region pain is lameness related to osteochondrosis lesions, OCD, and subchondral bone cysts. In North America, subchondral bone cysts of the medial femoral condyle are rarely seen. Horses with subchondral bone cysts are treated by rest, injection with corticosteroids, or surgery. If radiographs reveal evidence of OA, such as enlargement of the medial tibial plateau, or if ultrasonographic examination reveals flattening, wrinkling, or other change of the medial meniscus, then the prognosis for racing is diminished. If subchondral bone cysts are discovered early in training, horses are best managed with arthroscopic surgery. The prognosis for a horse with a sore stifle, ligament laxity, and intermittent upward fixation of the patella is good, assuming a favorable response to alterations in training regimen. Lameness in Arabian racehorses with sore stifles appears similar to that seen in young TBs with tibial stress fractures, but the origin of pain is different. The prognosis for horses with osteochondrosis varies but is poorer if evidence of OA exists.

Back Pain

Primary hindlimb lameness causes secondary back pain in most Arabian horses, particularly those with primary lameness of the stifle and hock joints. Often back pain resolves after management of the primary hindlimb lameness. However, treatment of back pain concomitantly allows earlier resolution of both problems. Exercise riders or jockeys may suspect back pain and often report a sensitivity or soreness over the top line. Horses usually show pain on palpation or when pressure is applied along the back. The back is palpated carefully, and pressure should be applied uniformly and gently. Thermography has been of some value in horses with back pain resulting from a poorly fitting saddle. The saddle can be evaluated thermographically and compared with any warm spots on the horse’s back. Nuclear scintigraphy may reveal IRU in the summits of the dorsal spinous processes. Radiological examination may confirm overriding of the dorsal spinous processes. However, radiological and scintigraphic findings are often negative, and back pain is assumed to originate from soft tissues. Nonetheless, if back pain is severe, we suspect a bony source of pain. The back can be evaluated by ultrasonography, dorsally or rectally, for myositis, nerve root impingement or enlargement, and osteophytes associated with the vertebral articulations. Lumbosacral and sacroiliac pain is often detected in Middle East Arabian racehorses, and a positive response to pressure over the tubera sacrale may indicate that sacroiliac region pain is contributing to an abnormal gait, if present. IRU in the sacroiliac region can help establish a diagnosis, and one of us (AD) often injects corticosteroids in horses with this finding, not only to manage pain in these horses, but also to help establish a diagnosis.

Dorsal Third Metacarpal Bone Disease

Many racehorses trained intensely at speed at a young age experience the sore-shin or bucked-shin complex. Although intense training may not begin until the 3-year-old year and the Arabian racehorse is smaller in stature and weight than its TB counterpart, bucked shins remain a major cause of lameness requiring reduction in training intensity. Trainers are well aware of this problem and often can diagnose it accurately based on clinical findings and the observation of a sore horse, traveling short. A veterinarian usually confirms the diagnosis clinically, but in some horses radiography and occasionally scintigraphy are necessary. With advanced dorsal McIII cortical pain, typical dorsal cortical periostitis or a dorsal cortical fracture is seen radiologically (see Chapter 102). With periostitis comes intense, diffuse IRU, whereas focal IRU is seen in horses with a dorsal cortical fracture (see Chapter 19). However, scintigraphy is used more commonly to diagnose stress-related bone injury and stress fracture of other long bones in Arabian racehorses. Conservative management is preferred with rest, reduction in strenuous training, or return to the layup farm. Pin firing and blistering are not used routinely. Dorsal cortical fractures are rare, but if present, one of us (MCR) prefers surgical management using osteostixis (dorsal cortical drilling) or insertion of a bone screw placed in lag fashion in the dorsal cortex of the McIII. The prognosis is good.

Although this condition is recognized in Middle East Arabian racing, it does not appear to be as common as in North America, and horses are usually successfully managed conservatively.

Fractures of Various Bones, Including Stress Fractures

PSB fractures do occur in Arabian racehorses but are less common than in TBs. Clinical signs, management, and prognosis are similar to those in the TB racehorse (see Chapter 36). Other fractures, such as midsagittal fractures of the proximal phalanx and condylar fractures of the distal aspect of the McIII, are rare in North America. However, in the Middle East both medial and lateral condylar fractures of the McIII occur quite commonly. Lateral condylar fractures predominate. Horses with fractures of the proximal phalanx and condyles of the McIII are managed surgically. Less commonly, humeral and tibial fractures occur. Complete fractures are easily diagnosed and necessitate immediate euthanasia. Horses with humeral and tibial stress fractures often require scintigraphic examination for diagnosis but have a good prognosis if fractures are recognized early when incomplete and the horses are properly given complete box rest. Pelvic stress fractures are being recognized more frequently in Middle East Arabian racehorses; one of us (AD) believes that these fractures have been underdiagnosed. Scintigraphy usually produces a conclusive diagnosis. Avulsion fractures of the origin of the suspensory ligament from the McIII with or without associated PSD occur in the forelimbs and hindlimbs, cause acute-onset lameness, and are commonly diagnosed in the Middle East Arabian racehorse. Conservative management is successful, but prognosis is adversely affected by concomitant PSD.

Proceeding without a Diagnosis

Lameness in Arabian racehorse should be investigated in a logical manner as with all lameness examinations, taking into account the usual wishes of the owner and trainer to retain the horse in training if possible. In some horses in which joint pain is suspected but clinical signs are vague, a concurrent intraarticular injection of hyaluronan, corticosteroids, and local anesthetic solution can be used as a diagnostic and therapeutic approach. Occasionally, lameness is suspected but a diagnosis cannot be made. Horses with such lameness are characterized by a drop in performance, an increase in race times, a subtle gait change, a refusal to switch leads, a drop in class, or soreness, but no clinical signs of overt lameness are observable. In this situation, we usually recommend a whole-body scintigraphic examination, but correlating findings with clinical signs is often difficult. Comprehensive evaluation for poor performance considers not only a musculoskeletal problem but also cardiovascular and muscle abnormalities. Sometimes, Arabian horses may be thought to be more fragile and highly strung than other racehorses, and some trainers attribute poor performance to this portion of the horse’s personality. However, Arabians are used for endurance riding (see Chapter 118), in which average speeds of more than 25 km/hr are often sustained over a course of 120 km, a fact that confirms the breed’s strong metabolic endurance characteristics. One of us believes strongly that if an Arabian cannot endure race training, there is invariably a musculoskeletal defect or injury (AD).