Asynchronous Joint Rotations

February 13, 2019

Joint surfaces are not symmetrical like a door hinge or a ball and socket, and that makes the limbs rotate during flexion / extension. Watch the hind limb at the stifle joint and it should be obvious that the motion of the limb does not follow a straight line in the direction of the motion of the horse. Healthy kinematics includes limb rotation in a specific synchronization with the phases of a stride, determined by the way the particular horse is put together. In unhealthy kinematics the synchronization is wrong – asynchronous, and when that is repeated over and over, it is a form of overloading - repetition stress injury results. When the motion is in the state of consistent repetitive overloading, new CPG’s need to be created to prevent, slow or stop pathological changes that lead to lameness. 

February 13, 2019

Central pattern generators (CPG's) are neural circuits, sort of like little computer apps, that make locomotion, heartbeat, breathing, and other functions, automatic.  For soundness in horses, we are concerned with locomotor CPG’s; the one’s that maintain pattern of motion like walk, trot, and canter. That saying “running around like a chicken with no head,” yeah, it’s gross, but it’s real and it provided real repeatable experiments for scientists to learn about CPG’s. Locomotor CPG’s work without the brain attached. (For more on this, you can read the following review paper:  “Central Pattern Generators and the Control of Rhythmic Movements” by Eve Marder and Dirk Bucher, published in Current Biology Vol. 11, No. 23.) This is important because protective kinematics will create CPG’s. With injury, lameness, muscular imbalance, or discomfort, the compensatory movement creates new CPG’s that create kinematics associated with overloading joints (see my article Overloading).  Working on a standing horse, whether it be releasing tight muscles or injecting joints, does nothing to create new CPG’s. Motion is required. The only fair solution is to create new CPG’s for healthy kinematics. It’s not done by repeating the same work and hoping the horse will figure it out. It’s not done by following a regime of prescribed exercises. Usually, they don’t figure it out. Pasture rest doesn’t create healthy CPG’s, it just continues the repetition of dysfunctional kinematics. The only way to create new CPG’s is by creating precise, correct kinematics. This will create healthy CPG’s that aren’t overloading joints. It will also increase efficiency and athleticism.


February 28, 2019

The word “position” is a little misleading because the word itself implies no motion.  Riding is all motion and position is constantly changing.  As a young equitation rider, my position was important. The aesthetically pleasing position was rewarded in the show ring. This training is intended to create a solid foundation for a rider.  One of the side effects of intense focus on rider position is that often it mentally disconnects the rider from the horse and blocks the rider from feeling the horse.  But position is important because the forces the rider receives from the horse are very high and must be efficiently managed through the rider’s back or there will be damage and pain. Position can also be the difference between an explosion and athletic serenity in a highly reactive horse. It can be the difference between overloading joints and healthy locomotion. So, we approach position from the horse up, focusing on how the forces produced by the horse are managed by the rider and vice versa. When the rider and horse find the most efficient body coordination, the natural consequence is a peaceful, quiet, beautiful pair. You can’t talk about rider and not the horse. The moment you combine horse and rider, there is a new system – a mutually dependent interaction between horse and rider. The horse’s muscular actions affect the rider and the rider’s muscular actions affect the horse.  The two cannot be separated if you want the fastest path to efficiency.  Knowing how the horse’s body works is what makes it possible to know what adjustments to make to help your horse to help you. With a rider in correct position, a horse can still make errors. Dysfunctional kinematics in a horse will place the rider in dysfunctional position.  The rider needs to understand this or either confidence is smashed or the rider goes to using too much force. Horses don’t require a lot of force. Riding doesn’t require great strength – just sophisticated balance control.  

January 11, 2019

You hear or read about overloading joints.  It leads to lameness.  Some people will tell you to protect the joint, you should inject some stuff into the joint fluid. But what is it really to overload a joint?  If you overload your truck with too much hay it you can see that it is overloaded. It squats in the back, the front end is higher and lighter and maybe it has sketchy steering. If you keep doing that, something is going to break sooner than it would if you didn’t do that. The common way of overloading a joint of a biological system, the way we either cause lameness from riding, or fail to prevent it, is different in most cases. (This is not to say you can’t put too much weight on a horse!)

I saw yet another worn out hair elastic on my dresser. They don’t last very long; it’s maybe 150 installations or so before the elastic has pulled out of the clamp. I thought; this could be a good way to illustrate joint overloading.

MECHANICS FOR EQUESTRIANS II: Fatigue Failure – 11/7/2016 Paige LaBella, BSME

I was inspired by presentations at the 2016 SOM Conference, which as usual, were very informative and engaging. During a presentation, a question was asked regarding the presenter’s decision to analyze compressive forces on the navicular bone under dorsiflexion. From a mechanical engineer’s perspective, it makes perfect sense in the realm of material failure analysis and so I am motivated to share some engineering knowledge.

To determine the various strength limits of engineering materials, a sample of the material is destroyed and the forces are recorded during the destruction. The maximum force applied just prior to failure (breaking) is, in general terms, the strength of the material. I get a stomach ache when I think about testing living bones the way we test engineering materials, so let’s use steel as an example.