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What does the science say about staring young horses?

I know there are plenty of threads discussing the topic of starting 3 year olds and it can be a rather controversial subject; however, I haven’t seen one up to date that discusses the actual scientific evidence on both sides and I am curious what the jurisdiction is based on that evidence.

I have heard both sides of the topic: (1) that starting early may contribute to later soundness issues, which may result from premature weight baring and (2) that light weight baring early-on may facilitate bone re-modelling during the growth phase, lending to prevention of breakdown.

Moreover, I have a question regarding genetic predisposition of breakdown/soundness and whether this may be an extraneous variable explaining why the evidence is so contradicting in this topic? There is various accounts of performance horses, particularly those in dressage, being bred for movement and losing longevity. I recall one thread on here, where a german vet was discussing the topic in dressage bred horses. Linked: German vet discusses flawed breeding and issues with movement I’d love to hear thoughts on that.

I thought this may be an interesting conversation to have to discuss both sides of the topic in regards to the evidence available.

I don’t have the links handy, but:

If I’m remembering correctly from the Maryland Shin Study and similar, “light weight bearing early on” doesn’t facilitate bone remodeling. Short bursts of hard work are what facilitate bone remodeling; for young racehorses, that means working at racing speed or close to it.

I don’t know if any studies have looked at this with sporthorses. Sporthorses also don’t need as much bone density as racehorses.

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I’ve heard this a lot from various people but there has been very little evidence presented in those conversations. For example, the idea that high knee actions leads to unsoundness in dressage horses, however, gaited breeds or carriage breeds do not necessarily seem to suffer from knee action.

I hope someone can share some studies on that topic.

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I think both sides are actually in agreement. One side says start the horse early in some sort of light version of their proposed career to encourage the correct development of bone and connective tissue, while the other says, the horse isn’t mature, so don’t be impatient and over work the horse in an arena doing repetitive circles and advanced movements.

Both seem to avoid the more sticky topic, that is how stabling/confinement of horses in training may be the bigger evil when it comes to hindering the healthy development of a horse. Developing horses need to move, and do hills, and meander over uneven terrain.

As to the high knee action? Our neighbour used to take in retired saddlebreds, and they were retired quite young (late teens), but I have no idea if that came from the high knee action, or the shoeing/confinement at a young age.


Thank you for clarifying! I read about it years ago and couldn’t remember the specifics; however, that makes sense!

I linked the thread/ video I was referring too in the edit above. I’d be interested in seeing some further studies as well!

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The science is actually pretty clear on this. Michigan State recently published a comprehensive review of equine bone development research: https://www.mdpi.com/2076-2615/13/5/789?fbclid=IwAR1XpF8jq8fScpbGynWckhTa_HgBBPEh_rkvHmYW8xsbwejPmhHY7ecA3jk&mibextid=Zxz2cZ.


I know this is an older topic, but as I watch the European event horse auction videos of 3 yr olds schooling cross country on a lunge line and and 4yr olds doing a full course I had the same question. There’s so much pressure to get young horses farther along in their training including the Young Event Horse program. I wonder what the costs are? I know that schooling cross country slowly on a lunge is different than having a ridder on, but they look so well schooled that it must be a regular part of their training. Do these ISH hold up? They certainly dominate the higher levels.

Personally, I think xc schooling on the lunge isn’t a great thing. It’s not natural for horses to jump a sizeable fence, and immediately turn two strides after landing. In the videos it looks quiet and smooth, but in real life I bet there are plenty of spins at higher speed with a rough turn as the horse is learning. It’s good for them mentally, to be eager in their job and learn to handle their bodies without rider interference. But it isn’t without physical wear and tear.

I would MUCH, MUCH rather be on the horse’s back, with a straight approach and a straight canter away on landing.

It’s my own personal philosophy to avoid circle work, and do very limited round pen/lunge work on anything under age 4. I do back my horses young (at racehorse age) but I get them out in the fields ASAP working in straight lines.


Most horses like to chill out and not do much work, then go for a nice sprint. I think sprinting helps with bone development. But I also think that because horses are often confined they are more likely to hurt themselves running like fools. Therefore, forced exercise of some sort helps prevent them from feeling so good they go out and hurt themselves.

I free lunge my young horse and try not to encourage him to gallop. A nice trot is all I really want. Any horse just doing flatwork is probably going to have less wear and tear then a horse asked to perform over jumps.

Low intensity exercise is probably a lot easier on the joints than high intensity exercise. Some high intensity exercise is good for bone development.

The fact is we cannot select specifically for soundness unless we only breed older horses that have already had a career and have proven they will stay sound in hard work. Things like arthritis and degenerative ligaments often don’t show up until later in life and are hard to select against. Is the horse lame with arthritis because he had a difficult career or is he lame because he is prone to arthritis to begin with?


I agree horses shouldn’t jump “sizeable” fences on a circle, but schooling xc on the longe should not be over sizeable fences. I longe over BN max, and usually just starter. The point is to teach the young horses to figure out the problem on their own with very minimal human guidance. I want them to figure out how to jump without my body weight and I want them to learn the puzzle and learn that it’s fun before I introduce a rider. Lastly, no matter how hard you try, there will inevitably be times where an awkward jump puts you off balance. By longeing over the fences I find those times are minimized, as the horses have time to see the fences and learn about them before I’m on their back.


I like to pony them, a lot of western people I know will pony a colt regularly on trails for a year before they ride it, on all kinds of terrain. It teaches them a lot of good things and I think it’s very useful education for a baby. Mostly at the walk, with a bit of slow trotting here and there. They learn about ditches, water, bridges, manners etc. Similarly in Europe a lot of people will ride the mare and let the foal follow in the arena or around the farm and introduce them to things that way.


Yes, I was ponying him with his mother but he’s too old to do that (until he gets gelded).

I wish somebody would find a ‘t’ :wink: