Bramlage: Racing And Training 2-Year-Olds Reduces Their Risk Of Injury – Here’s Why by Natalie Voss|05.04.202012.07.2020|6:14pm4:48pm Before most horse racing jurisdictions shut down across the country and threw the economic balance of the sport into question, the industry's biggest problem was its need to reduce racing and training fatalities. Veterinarians and scientists are still learning about the causes of catastrophic injuries and, so far, it seems there may be a number of risk factors at play in any given injury. One theory that many people have offered over the years is that the practice of allowing horses to race at two years old is either the direct cause of early breakdowns or predisposes horses to serious injury later. Many such hypotheses equate training and racing a 2-year-old with putting an elementary school-aged child into the Olympics. For more than two decades, the sport has heard calls to put an end to 2-year-old racing. Those calls have been renewed recently, as some fans have seen the racing shutdown as a good time to reevaluate and modify its structure and improve equine welfare. The problem, according to Dr. Larry Bramlage, top orthopedic surgeon and Rood and Riddle Equine Hospital, is the halt of 2-year-old racing and training wouldn't be a net gain for welfare or fatality rates – it might actually be a loss. Understanding why requires a deep dive into the process of bone development and skeletal growth. Firstly, Bramlage said, horses grow much, much faster than humans do. One study in the 1970s showed light horse breeds reach 84 percent of their mature height by the time they are six months old, and 94 percent of their mature height at 12 months – about 3 percent of the way into their life expectancy. This may be because they evolved as prey animals and, like other spindly-legged baby prey animals in the wild, needed to reach maximum height and stride length as quickly as possible to better enable escape from a predator. Humans, by contrast, get close to mature height between the ages of 16 and 18 – about 23 percent of the way into their life expectancy. Long bones, the type of bone found in horses' legs, grow and change in a few different ways. One way is by lengthening at the site of growth plates, which are situated at either end of the bone. You may have seen charts showing the timeframes for growth plate “closure” – meaning the age at which those growth plates stop actively adding new cells to extend the bone's length. Growth plates close from the ground up, so ankle joints close before knees, etc. Bramlage said the growth plates in the lower legs (knees and below) are closed at about two years old. “They have a few growth plates like the withers that last for ten years, but those are not really of much practical significance when we're talking about injuries,” he said. Bones also undergo modeling, meaning they change in width and shape thanks to the work of cells that break down and build up bone. Modeling is directed by genetics. When an animal is young, most of the bone's cellular resources are directed at growth, but the cells focused on the modeling processes become obsolete as the animal reaches sexual maturity. For horses, sexual maturity happens anywhere from nine months to 15 months of age. The whole bone formation process with its cells and blood supply are designed to atrophy away once growth ceases. For a horse in need of extra skeletal strength, like a racehorse, the modeling process of growth changes to the remodeling process of response to exercise. The remodeling process for an individual horse will be better if more of that blood supply and cell population makes the transition from modeling to remodeling. “The support system for growth in the horse is tremendous,” Bramlage said. “The support system for bone growth is blood supply and cell populations. You have to have the osteoblasts, the cells that form bone, and you have to have the blood supply to support them. “If you don't train an adolescent horse, you let those populations and that blood supply atrophy; when you start training you have to recreate that again. And a horse can do that, but it's a much longer process to recreate that system than if you take advantage of the fact that it's already there, and it has already finished its first job.” Modeling brings a bone to its genetically mature size and shape, but it doesn't necessarily make it dense enough or strong enough to withstand athletic activity. For a bone to become stronger and denser, it needs to undergo remodeling. Remodeling happens in two ways: when the bone suffers micro injuries from the stress of training and then repairs itself to become stronger; and when the bone senses its size and shape are insufficient to handle the exercise load it is experiencing and remodels its shape. In the first instance, cells called osteoclasts remove damaged existing bone and osteoblasts replace it with new bone; in the second instance, the osteoblasts add bone in specific locations to improve the bone's shape based on the exercise it is experiencing. “The bone changes in relation to the load that it has seen,” Bramlage said. “You have to produce bone that's hard enough to withstand the load it is seeing and bone with the best geometric shape to withstand the loading. The horse's cannon bone is the prime example of where those processes are both underway during training. Overloading and over-repair is 'training' in all species.” So what does all that mean for 2-year-old racehorses? Bramlage said it means that turning a horse out until its third birthday and then beginning race training will adapt the skeleton to turnout for a year, but not to training or racing. The bone modeling system will largely atrophy. The horse is then introduced to training and will have to recreate the vascular supply and cell population devoted to remodeling. By contrast, the horse who trained at two only had to repurpose the vasculature and cells already present for growth. This can be complicated by the fact that the heart and lungs, which are oft-used indicators of a horse's fitness, don't respond to training exactly the same way as bone. Horses have such relatively large heart and lungs that they respond faster than the skeleton to training, especially when a previously sedentary horse begins training. Bramlage believes the horse who went through a year of turnout and began training at three is at greater risk of skeletal injury down the road because its skeleton may be less able to keep up the pace. Thanks to heart and lung conditioning, the rested horse may appear to be getting fit just as quickly (or even moreso) than his stablemate who trained at two, which could fool a trainer into increasing his workload too quickly for the skeleton. The data bears this out. Year after year, the Equine Injury Database has shown that 2-year-old runners had a significantly lower fatality rate than 3- and 4-year-olds. Preliminary data released earlier this year showed that older horses who had raced as 2-year-olds had a decreased risk of career-ending injury to those who had not. In 2008, Bramlage analyzed data from the Jockey Club Information Systems for runners between 1975 and 2000 and found horses who raced as 2-year-olds had more lifetime starts than those that didn't begin racing until they were older. Average lifetime earnings for those that had started as 2-year-olds were almost double those who had not, and average per start earnings and percent stakes winners were also higher for those who ran at two. “This data is definitive,” Bramlage told the Jockey Club Round Table that year. “It shows that horses that began racing as 2-year-olds are much more successful, have much longer careers, and, by extrapolation, show less predisposition to injury than horses that did not begin racing until their 3-year-old year. It is absolute on all the data sets that the training and racing of 2-year-old Thoroughbreds has no ill effect on the horses' race-career longevity or quality. In fact, the data would indicate that the ability to make at least one start as a 2-year-old has a very strong positive affect on the longevity and success of a racehorse.” But, he says, there is a caveat: horses are individuals. You can't expect all horses to respond to training exactly the same way at two years old or three years old. Forcing a horse who is not ready to make a start at two is not good either. That's why a trainer needs to be incredibly observant. “People have asked me, 'What do you think makes a good trainer?'” he said. “I think there's one thing that separates trainers from top to bottom and that's the ability to tell when a horse is happy, because horses that are training well and adapting well like to train. The good trainers can watch the horse and train them to the edge of their physiology but pick out when they're beginning to get behind, and slow them down or stop them.” Horses, like people, have a lot of individuality in how quickly they reach peak athletic ability. All horses experience rapid growth at relatively similar rates, but they don't all put the pieces together (bone, soft tissue, mental, cardiovascular maturity) at exactly the same point in their lives. A trainer has to know what type of individual they're dealing with, and they have to spot when that horse hasn't been able to adjust quickly enough to their workload. “When you went to school, there was probably one guy in your class that was shaving in the fifth grade,” Bramlage said. “That guy matured early and is going to be the best athlete early, maybe the first few years of high school. But they, for the most part, get passed up by those that mature a little later but mature a little further.” This factors into training for 2-year-old sales, too. Bramlage said there are especially precocious horses who do put all their pieces together at the right time to safely prepare for and enter a 2-year-old in training sale. Some do not. The trick is knowing, or quickly assessing, whether the individual can handle the pace of training. One of the most difficult things about injury prevention is that veterinarians don't have hard and fast rules to know how long a stress/repair cycle is for bone after a hard bout of training or a race. This makes it harder to strike the balance between challenging the skeleton enough to improve bone strength, while giving it time to adjust before challenging it again. Bramlage said recently, members of the Jockey Club's Thoroughbred Safety Committee have analyzed data on starts and auction appearances and found that each trip through a sale ring – yearlings and 2-year-old sales – increases a horse's probability of ultimately making a start. There is some selectivity to that data, however, because horses who can't stand the rigors of preparation for a breeze-up sale probably don't end up going through the sale. Bramlage said the same is true for yearlings prepping for sale: some respond well and some are slow in responding. “There certainly are horses who can't stand training against the calendar, because that's the whole difference,” he said. “Horses that are able to do that, get selected out of the group. You've selected the horses that stand up to training earlier and better. Our whole racing calendar rewards precocious horses with entry-limited and purse-supplemented races during their 2- and 3-year-old years. But there are certainly later maturing individuals that ultimately reach higher levels. “What people have to realize is there is a population of 2-year-olds in training who could suffer from the 2-year-old in training sales if you're not cognizant of the fact they are not responding fast enough. If you keep trying to train them, they can get injured. Training is an art.” What about training horses at two and waiting to let them run at three? Or preventing injuries by focusing on long, slow work and avoiding speed? The science doesn't support that, either. “Monotonous training is not good for the bone,” said Bramlage. “This idea that we're going to gallop them lots and lots of miles and that way we'll make bones stronger and stronger doesn't work. Bone trains to the level of exercise, not the amount. Hearts and lungs and muscles, they train a lot to the amount of exercise, but bone trains to the level. “A horse's bone is going to get stronger at the level of his fastest furlong. But if he goes 10 furlongs in his training exercise, the last nine furlongs are actually wear and tear on the bone. If you continue that wear and tear over and over, the skeleton may not keep up. So, putting lots of monotonous exercise on a horse doesn't get you a stronger skeleton. Training at a gradually increasing level without overdoing it does get you a stronger horse.” Ultimately, the questions surrounding 2-year-old racing and training don't have simple, black and white answers. If the evidence was clear and unanimous that one course of action (like eliminating or mandating 2-year-old racing) was likely to improve equine safety, then rule-making would be easy. As it is, Bramlage points out that there are no peer-reviewed studies that have shown training and racing 2-year-olds increases their risk for injury. Like so many other aspects of training and management, making the right decision is an art, which should be informed by science.