An ongoing controversy in the racing industry is whether training and racing young horses is detrimental to their growing bones. Naysayers claim athletic demand on immature bones causes them to break, but scientific research supports early training, because bone is living, dynamic tissue that becomes stronger and more resilient in response to the demand placed on it.
Graduate student Alyssa Logan at Michigan State University wanted to see how much exercise is needed to trigger the bones of young horses to become stronger. Amazingly, her research found that sprinting about a third of a furlong just once a week is all it takes.
Because sacrificing weanling horses at the end of a study is socially unacceptable, Logan chose calves destined for the MSU beef program as her study animals. How could a study investigating the effects on young racehorses draw its data from calves?
An aside to this story is that Logan's co-researcher and adviser, Dr. Brian Nielsen, set the world record aboard his racecow “Taffy” for the fastest mile ever recorded by a cow being ridden under saddle on a racetrack. While pursuing his Ph.D. in equine exercise physiology at Texas A & M University, Nielsen also broke and galloped racehorses, including Texas Horse Racing Hall of Fame filly Two Altazano. Eventually, he earned his racehorse trainer's license in 1997.
At nine weeks old, 24 calves were divided into four groups: sprinting one day/week; sprinting three days/week; sprinting five days/week; and no sprinting (control group). The sprinting calves were herded 71 meters down a barn aisle with a concrete surface, while the control group was contained in stalls for the duration of the study.
Although it would seem that calves sprinting on concrete wouldn't generate results similar to horses sprinting on dirt, Nielsen explained that the force of impact is calculated by a formula combining speed and surface.
“Running these calves on concrete and at a slower speed is similar to the results we see with horses running faster on dirt,” Nielsen said.
Over the six-week study, calves sprinting one day a week logged a total of 426 meters at speed, or two furlongs. Yet their bones became more than 20% stronger than sedentary calves in the control group. The other sprinting groups also developed more than 20% stronger bones.
The study was published in the Journal of Animal Science and is available here.
“To me, what was earth-shattering was how little speed it took, but it did take some speed, to have a tremendous difference in bone-breaking strength,” Nielsen said.
Nielsen emphasized that some of the routine practices for managing young racehorses, including Quarter Horses, could predispose them to injury. Sales-prepped yearlings spend months in a virtual bubble-wrap cocoon to guard them from injury. They aren't turned out to play, and exercise is limited to hand-walking and/or non-weight-bearing water exercise. When the buyer takes the yearling home to break, it spends at least three more months just walking, trotting, and galloping—but no speed work.
“When the horse is relatively fit, you begin to put speed work on him, and he bucks shins and you're wondering why,” Nielsen said. “Actually, the bone has become weaker during that time of them not doing anything at speed. So it's not surprising they develop bucked shins. … We have so many people who are gun-shy about putting speed on horses because they don't want them to break down. But a little bit of speed is absolutely critical.”
Exercise for young animals is critical because the bone is more responsive in growing horses than in older ones. Even foals housed with their dams and young weanlings in groups need to have access to free exercise to set them up for better bone later in life, Nielsen said.
He advised farm managers to pay attention to the groups their horses are in. For example, a weanling with an aged horse as a babysitter will adopt its sedentary lifestyle, while a group of weanlings will run and play together to achieve the sprint speed needed for good bone health.
“A lot of times you'll see weanlings housed individually in their own paddocks,” Nielsen said. “I certainly would not recommend that because it limits how much movement they do on their own.”
Nielsen differentiated between a sprint and a fast gallop, known on the track as a “two-minute lick,” the speed it takes for a horse to complete a mile in two minutes.
“I want the horse to go just about as fast as he can,” Nielsen said. “I really want him to dig in a little bit. The two-minute lick is a much more controlled speed, and it's not going all out. You want to signal to that bone that it needs to become strong and it needs to maintain that strength.”
With a typical Thoroughbred's stride length being about 20 feet, a 71-meter sprint would consist of just a dozen strides at speed. In training his own young racehorses, Nielsen asks them to sprint in the middle of their gallop.
“Part of the reason for that is they're not tired yet,” he said. “You're going to bring them up to speed and bring them down pretty quickly. We finish out the gallop, and they're calm and relaxed.”
Nielsen said where the trainer inserts the sprint depends on the individual horse and the trainer's preference. Some trainers may want to put the sprint at the end of the gallop to teach the horse to give its all at the end of a race. But Nielsen said speed at the end of the gallop, when the horse is tired or tiring, could make the horse associate speed with discomfort.
“So much about training horses is to get them mentally correct, and you don't want them to hate or dislike going fast,” he said. “If you put it in the middle of the gallop, it keeps them mentally sound. That's what my past experience dictates. There will be enough times when you're doing a regular work where you'll ask the horse to finish big at the wire, so I think you're going to accomplish that there.”
Nielsen said the big take-home message is that you don't want a horse to go weeks without any speed work because it will weaken the bones. Even if the horse is just buzzing around a paddock or sprinting 50 to 70 yards in training, the speed work signals the bone to get stronger.
“If you have periods of time longer than a week without horses sprinting at all, whether it's with a rider on the back or just being turned out, I think you're putting your horses at risk for bone loss,” Nielsen said. “Whereas this study would suggest if you can get them either turned out or have a short sprint at least once a week, that would be a smart approach to take.”
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