Brian Nielsen, Ph.D., Professor, Department of Animal Science, Michigan State University Guest Editorial
Dr. Brian Nielsen at the Michigan State University Teaching and Research Center.
If you are willing to be open-minded and are truly interested in what is best for horses, I would suggest clicking on the link below and reading the article to which it takes you.
My Ph.D. student, Alyssa Logan, and I just published this review article about this topic in the journal Animals. Unlike a lot of scientific articles that are not available to the general public without paying to read it, we opted to make this one “Open Access” so it can be read for free. This review article cites 65 other papers on the topic.
In brief, some major points of the review:
Tissues can adapt to exercise greatest while immature and still growing. Once mature, many tissues lose that ability.
Confining animals and not allowing any sprinting to occur is detrimental to overall tissue strength.
Masking pain through medication (such as corticosteroids) to allow an animal to continue to exercise does not cure the problem. It often simply hides the problem and allows the animal to damage the tissue further.
Most horse people care deeply for their animals and only want the best for them. However, there can be much disagreement about what that constitutes. One item that draws deep passion and division is whether it is acceptable to start training horses while they are young and still growing – or whether one should wait until they are fully mature.
Having made a career out of trying to improve the lives of horses and having a research program that focuses on injury prevention by studying how bone and cartilage respond to growth, nutrition, and mechanical loading, the science is very clear. Researchers who work in this area from all over the world tend to agree. These tissues (and tendon would be included also) have much greater ability to adapt while young and have the capacity to adapt. Once mature, they lose that ability.
For those who aren’t interested in reading the entire scientific article, but would like some more information, I encourage you to keep reading.
It is true that horses are not skeletally mature at two years of age. Neither is a 16-year-old high-school student, but few would say high-school students should not participate in sports if they want to be good athletes. If tissues are not challenged when young and malleable, they will never achieve their maximum strength. With humans, to be a good athlete, we would not encourage them to wait until they are in their 20’s and fully done growing to begin to train. However, that seems to be what is suggested for horses.
Speed is good. Lack of speed is bad. Too much speed when tissues are not prepared for it is bad. When we put horses into stalls and they don’t get to run around and play, tissues don’t gain strength and often even get weaker. The result is a horse that is ill-prepared to be an athlete and prone to getting injured. Comparatively, humans who start running after having led a relatively sedentary lifestyle often develop shin splints as microfractures begin to accumulate in the bone. When this happens, the accompanying pain is simply the body’s way of saying “Stop doing this – you are creating damage and it needs to get repaired before there are major problems!” Shin splints are much less likely to occur in someone who has consistently had activity involving fast running than in someone who has done none and then starts to do some. Horses respond the same way. If they are consistently allowed to or encouraged to sprint, bone loss associated with disuse never occurs. For the most part, the old adage “use it or lose it” applies to bone.
Can overuse occur? Absolutely!!! And that can occur regardless of age. One of the biggest problems we have is people opting to use pain-masking medications (corticosteroids would be a great example) to cover up a problem instead of giving horses rest and time to recover. I believe one reason why people who opt to wait until a horse is skeletally mature to begin training may avoid serious injury is that they are often more likely to give a horse needed rest if a problem begins to arise. In reality, that is what everyone should do. We, the equine industry as a whole, need to quit masking problems – regardless of the age of the horse. When we start to listen to our horses and quit hiding problems, our big problems will begin to disappear. It really has nothing to do with age.
That being said, many horse people are under the belief it is wrong to start training a horse before its knees are closed. However, I know of only one research study that properly tested whether this is true. As mentioned in our article:
In 1973, the Australian Veterinary Journal published an article by Mason and Bourke determining the relationship between unsoundness in two-year-old Thoroughbreds and closure of the distal radial epiphysis. This study determined that at the end of the two-year-old season, 77% of horses that started training with open epiphyseal plates remained sound, while only 55-56 % of horses with intermediate or closed epiphyseal plates remained sound. The authors stated, “Many horses with open epiphyses raced six or more times and remained sound while numerous horses with closed epiphyses became unsound before their first race or before completing six races.” They also noted that horses with closed epiphyses showed greater incidence of lameness and poor performance. Ironically, the authors attempted to justify their findings, which were in contrast to common belief, by suggesting that the horses with early closure of epiphyses may have had an unknown nutritional factor that caused a “generalized skeletal dystrophy”.
To paraphrase the lines from the 1992 movie A Few Good Men: “You want the truth? You can’t handle the truth!”
The authors of that paper found out the truth. Waiting until the knees were closed to begin training caused more horses to be injured than did starting training while the knees were open. They couldn’t handle the truth as it was different than what they wanted to believe so they tried to come up with a reason to explain away the truth. I don’t blame them. That was 1973. Our knowledge of how bone and cartilage respond to mechanical loading has greatly increased in the 48 years since.
If you want the truth and to know what science actually says about the issue, I encourage you to read the article. Again, you can do it for free! (Just click on the link above, and then hit the blue button for “View Full-Text” or “Download PDF” after you are taken to the webpage for the article.) I realize there are many who will still not accept the truth as it differs from what they have been taught all their life. Strong beliefs are hard to change. However, even if you are not willing to accept that truth, there are many other points in the article that help to explain how we can prevent training-related injuries to horses of all ages – again, with one of the big ones being that we need to quit masking pain. Pain is there for a reason. It is the body’s way of saying “Stop doing what you are doing.” If we take away that message, we have removed the body’s warning signal.
Still have questions? Read our review article with an open mind! The article pretty much summarizes my thoughts on the topic and the general state of knowledge in this area. I will continue to spend my time working in this area to keep improving the lives of horses. After all, that is what most of us really want!
Logan AA, Nielsen BD. Training Young Horses: The Science behind the Benefits. Animals. 2021; 11(2):463. https://doi.org/10.3390/ani11020463