Research conducted at the University of Pennsylvania suggests that young horses should be given short, fast workouts early in their training program (e.g., one- to two-furlong gallops). These short periods of hard exercise might provide the appropriate modeling/remodeling stimulus without creating undue stress on joints, ligaments, and tendons.
The economics of Thoroughbred racing are such that most owners and trainers aim to have their horses ready for racing as 2-year-olds and, depending on ability and potential for use as breeding stock, for that horse to race for as long as possible. On the other hand, we know that lameness problems are the most important reason for wastage in Thoroughbred racehorses, and some perceive that these injuries are due, in large part, to the training and racing of horses too early in life.
Is this fact or fiction? The short answer is that we don't know. However, recent epidemiological studies by Craig Bailey and colleagues from the University of Sydney aimed to shed further light on causes of wastage, at least under Australian training and racing conditions. As in the United States, considerable emphasis is placed on 2-year-old racing in Australia.
In one project, researchers studied the racing careers of 553 Thoroughbred horses catalogued for a yearling sale in 1991. Of the 553 horses, 279 (50.5%) had their first start as two-year-olds, 162 (29.3%) as three-year-olds, 20 (3.7%) as 4- or 5-year-olds, 81 horses (14.6%) did not make it to the races, while the remaining 11 horses were lost to follow-up.
Surprisingly, horses having their first race during the 2-year-old season had longer racing careers than horses first racing at three years or older. The reasons for this difference could not be determined. However, it is likely that many of the horses not raced until they were three years old or older did enter training as 2-year-olds, and injury (or possibly a lack of athletic ability) might have delayed their racing debut. These factors also could contribute to a shorter racing career.
Bailey and his colleagues also examined injury rates in a group of 169 2- and 3-year-old racehorses. As mentioned, the most common injury in 2-year-olds was shin soreness -- which was present in 42% of 160 horses which began training as 2-year-olds. Many of those horses developed shin soreness a second or third time as 2- or 3-year-olds.
In 3-year-olds, knee problems were the most common cause of lameness, while fetlock injuries were present in both age groups. Injuries to tendons and ligaments were much less common, as were very serious breakdown injuries. Overall, days lost to training because of injury or illness were higher in 2-year-olds (3.1%) than in 3-year-olds (2.2%), probably reflecting the greater impact of shin soreness in the younger horses.
Most racehorses begin training at 18 to 20 months of age, a year or more before the skeleton has reached full maturity. Potentially, intensive training at that young age might predispose the horses to career-limiting injuries. Recently, practices associated with the preparation of horses for "2-year-olds in training sales" has heightened welfare concerns relating to the early training of Thoroughbreds. Because these sales are held in early spring, horses must enter training at even earlier ages to be ready to perform a racing speed workout as part of the preview process at the sale. The level of fitness required for "race readiness" necessitates an intense training program, and some of the youngsters might not stand up to such a rigorous preparation. The end result could be serious injury and the potential loss of a promising racing career. Indeed, there have been anecdotal reports of breakdown injuries in horses being prepared for 2-year-old in training sales.
The biggest unanswered question relates to the issue of 2-year-old racing. Yes, it is true that injury rates in this age group are high. However, this is also the case for older racehorses. And we now have evidence that horses beginning their careers during their two-year-old seasons actually have longer racing careers than horses which first race in later seasons. As well, on-going studies of the effects of training on the body at a very young age indicate that we should be training horses before the skeleton is fully mature.
Thus, on balance, there is a sound rationale for racing horses at a young age. That said, there is a real need for research that provides greater understanding of the causes of lameness problems in young horses and the effects of training methods and surfaces on the incidence of these problems.
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Почему при том, что всё вроде бы известно, возникает столько споров? Неужели только из-за "повального дилетанизма"? Сомневаюсь, что это единственная причина. Лошадь - существо, конечно, загадочное и неповторимое, но не настолько, чтобы возраст той же заездки мог плавать от 1,5 до 8 лет :roll: (разговор идёт о безопасном для лошади и всадника возрасте). Наверняка, есть какие-то ориентиры (не только кобыла/жеребец или раннеспелый/позднеспелый, но и что-то иное), которые хорошо бы иметь ввиду. Да и при такой "повальной безграмотности" что-то мало желающих провести ликбез, почему? 
