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Biomechanics For Riding: The Basics
2011/07/03
Biomechanics for riding is a science concerned withinternal and external forces acting on horses and riders. Biomechanical riding focuses on effects produced by these forces, with an eye to understanding efficient ways to achieve some desired effects for various equestrian disciplines. It has practical meaning for training horses: we can know how to prepare horses for their specific equestrian disciplines by working with them in ways that enhance how they are constructed. I will show some video frames and a computer model output to explain an approach to horsemanship that biomechanics offers.
The “illustrated horses” below show how important it is to develop “x-ray vision” to see how you and your horse operate.
From the outside view, if you sit in the “sweet spot” over an “X” of the big surface back muscles, mechanics of each move you make or each position you take can dynamically affect the horse’s muscles. Symmetrical development of muscles in an elastic fashion is a critical factor for balance. Balance is important for a training program that develops gymnastic capacity. We will come back to this at the end of the article.
Filename: MuscleHorseRider
Deeper in the horse, its body is held together by a connective tissue system called “deep fascia.” Deep fascial connections set up the skeleton to operate with most of its thrust from the hindquarters with stability architecture dominating the forequarters. Even though the front and back ends of a horse share thrust and stability, a biomechanically aware trainer keeps access to forward driving power from hindquarters in mind for the equestrian discipline desired.
Deep fascial structures binding its skeleton govern how a horse can respond to demands of its discipline. Actions of muscles are subject to this deeper anatomy.
Filename: DeepFascia
Some principles apply to any discipline or breed. Here are a few of those biomechanics concepts with some examples. There are instructions in the image showing a series of video frames on how to do some basic biomechanical analysis in your own riding environment. Rewards for this evaluative work are a sharpened “eye” for what your horse does and the road to development of a training program for healthy progress of gymnastic performance. Working a horse as it is constructed improves its comfort, attention and confidence. An attentive horse learns quickly and a confident horse is safe to be around.
Kinematics, with its connection to distances traveled and displacement of body parts, is the study of motion with a timeline, sets you up to look at speed and velocity (speed and velocity = distance traveled ÷ time taken). This approach is more do-able than some might think. Most folks have some good digital video or still cameras available and will be able to evaluate their horses with tools they already have. If you have download software on your computer, you will also need a basic movie making application and something like Photoshop to prepare sets of images like the ones with a timeline. Otherwise, still images will help with understanding you and your horse as a team.
This is an example of a kinematic study with a home video series. Its graphed timeline is prepared with computer software (Excel). Vulkan, my Württemberger gelding, shows the series of steps in medium canter. I used video editing software to take apart the movie frame by frame, then count the timeline with its velocity because the video was 24 frames per second (this takes patience!). I selected particular frames to show from the 0.63 second sequence for one stride. Because I worked against an arena fence grid of measured dimensions, I could compute rates, distances and displacements. You can make grids on an arena with colored tapes.
Filenames: MediumCanterSeries & medium-canter-L (graph)
Clear gaits are more than a feature to be judged at a show, they are crucial for healthy movement over performance lifetime. Legs work differently, depending on whether the gait is ballistic (bounding) or earthbound. Walking, including dressage walks, gaited walks, racking, singlefooting are earthbound gaits where the horse does not bound into the air. Ballistic gaits are trotting, cantering, galloping and racing pace. While muscles of the trunk operate the legs, they in turn act like inverted pendulums, transferring potential and kinetic energy to the trunk from the ground. Briefly, legs have the connective tissues that absorb those ground reaction forces. If a horse is worked over poor footing or drilled in movements with substantial acceleration components, effects of gravity can produce injuries.
Acceleration, where velocity changes with time, due to gravity (approximately 9.81m/s²), is based on a record of velocity. We will discuss some effects of gravity on your riding position and its effects on the performance of your horse. For instance, if you have barrel racers, racers, dressage mounts, reining or cutting horses, acceleration is a strong influence on sustainable or unsustainable performance.
These images are MODELS of potential to kinetic energy transfers in a horse’s legs during motion. Its selected frames show Leg positions during a stride respond to the acceleration of gravity. Because legs have significant weight (mass), gaits incorporate forces created by this mass and acceleration.
Filenames: Leg-walk & Leg-trot-canter
Below is a three-gaited horse with clear gaits. When you take still or video images of your horse or your riding, pay attention to all the phases of motion. At shows, most photographs are of “favorite” positions. While this can be helpful, there is important information in all moments of a stride.
This is another example of a kinematic study from a home video series. Its selected frames show leg phases plus suspension instants with the unique leg positons for each gait. Rio, my Rhinelander gelding, shows four phases of dressage gaits, where walking has no suspension (all four feet off ground in glide), trot (two suspensions, two beats) and canter (one suspension, three beats).
Filename: Walk-trot-canter
Forces we mentioned earlier respond to the equation Force = Mass times Acceleration (F = MA). Because horses have large bodies on spindly legs, nearly all riding disciplines place strains on their connective tissues (muscles, cartilage, tendons, ligaments, deep fascia, bones). It gets expensive if these tissues are injured, so a program based on understanding some biomechanical training will not only produce an efficient athlete plus save on vet bills.
If you include the direction and magnitude of forces, you will have vectors. These are important when understanding the work a horse must do to move around in any of its activities. Gaits of horses, whether three-gaited or more, produce strains on their legs and bodies that can be expressed as vectors. Forms of walk, trot and canter as well as pacing, tolt, paso corto or paso largo all have limb positions that are swing (in the air), toe-down, mid-stance or toe-off. When legs are on the ground, they are said to have a “duty factor,” a term I like because it means there is work being done. This work of muscles against gravity and friction can be in a training regime that builds fitness. Working too much in one sort of gait or exercise can run the risk of repetitive motion injury or lameness.
These images show how rider position affects a trot stride. A normal ground-covering stride can be produced by a rider in the default posture, where rider center of mass is just ahead of the spine below the rib cage. A horse is free to move without restriction from its bridle. In the other two postures, riders actively interfere with healthy motion because they shift their centers of mass. The rider who has pitched forward is also gripping with his (it is a male computer model of a skeleton) thighs, which prevents supple movement with the large back muscles (pink shades) that play a major role in moving legs. Misaligned riders produce irregular steps with their horses’ legs impacting the ground with timing of steps creating overload. By working with a short rein or behind the vertical with the horse’s head, they overstretch connective tissues in the top-line and their horse loses power thrust from behind. Riding with a shortened neck also chokes the horse at a time when it needs to breathe freely.
Filenames: Three-riders
Up to now, we have focused on your horse. What about you and your position when mounted? Your weight, alignment (right to left, forward to back posture), flexibility and coordination are critical factors in biomechanical riding. The default posture is balanced with respect to gravity. Each equestrian discipline will have variations on this posture. Here is a cutting horse (Morgan mare) with her rider in the default posture, allowing freedom of navigation, balance and agile response to a calf.
A cutting horse with balanced rider. Note that the horse has its legs placed to control her center of mass unified with her rider.
Filenames: Collection-cutting
Finally, we come to saddle placement. Too many trainers and riders position a saddle too far up on the withers. This practice interferes with the action of the shoulder blade and/or pinches the big muscle at the withers. Some horses tolerate this, but will be consistently hollow, going around in an “inverted” posture with a bulging lower neck. Gadgets like draw reins, longeing apparatus with pulleys, will generally not solve this problem, because horses are ingenious at evasions. If a horse is asymmetric in its body or gaits, the places to look for are rider position and saddle fit. In general, as a horse develops positively, the saddle of any discipline should be checked for fit and re-stuffed if appropriate. Further, the internal construction of a saddle should have a tree that does not irritate the back. If you place a saddle on a symmetrical form and its tree is distorted, it is worthless as an interface between you and your horse. An old saddle may be unsafe if its billets and construction have decayed.
This computer model of a saddled horse shows correct placement of tack away from interference with the shoulder and muscles over the withers. Large back muscles are not pinched if the gullet of the saddle is the appropriate width. It needs to be wide enough that the upward processes of the vertebrae are not rubbed. The girth needs to be of a material that is not stiff or irritating, plus adjusted safely without being too tight.
Filenames: MuscleHorseSaddled
The utility of this approach is that you can analyze the way your horse moves with or without your being mounted. And you can do it at your own pace, with the kind(s) of analysis you wish to make.
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