Ground Reaction Forces: you can’t avoid them

During a rebuilding phase, or any holistic training program for that matter, the interaction between gravity and your horse’s gaits must be constantly evaluated. In the past decade we have learned a lot more about ground reaction forces and their impact on different gaits. It is for this reason that I nearly always recommend a slow jog-trot during the early weeks of conditioning, despite the criticism from dressage riders that a horse must always practice the highest quality of each gait, with impulsion and suspension of the trot being a necessary part of rehab and conditioning. This is not only a faulty assumption; it is often harmful to the horse.

Many years ago, researcher and veterinarian Hilary Clayton performed numerous studies involving horses moving across force plates at different speeds. Her team determined that each forelimb experiences forces up to half of the horse’s bodyweight at walk, 100 percent of bodyweight at regular trot, and 1.5- to 2 times its bodyweight in canter.

Over the past few years, biomechanics experts have been able to further interpret these findings. In particular, a trot with higher levels of suspension and extension increases the peak vertical forces on each forelimb, especially when the horse is not ideally engaged. This means the load on each forelimb in many cases exceeds the horse’s bodyweight. That’s a lot of force to repeat stride after stride. Further, curved lines (circles, corners, bending) measurably increase forces on the outside forelimb. During canter, the outside fore also bears additional load (as a sidenote: this is partly the reason that some horses can feel so out-of-sorts on a particular lead. In the presence of shoulder asymmetry, the added load on the outside shoulder can create a rough ride.)

So, if you have an energized trot or canter with big swinging strides and you’re performing circles, you’re fighting gravity. Unless you have a horse that is fit and symmetrically muscled, you’re gambling with his lower limbs and connective tissues. Perhaps you will only create a bit of stiffness and soreness, but you also might create a setback if you are trying to rehab or re-condition your horse following a layup.

Slowing down the trot and canter is a vital, albeit temporary, rehab tool because when we slow the horse down and eliminate suspension, we reduce ground reaction forces. A jog, versus a trot, allows us to re-introduce aerobic activity and muscle activation at a much smaller risk to hooves, ligaments, and bone. If we can therefore avoid the stiffness and soreness, the horse forms a base of metabolic fitness that then allows us to begin improving his gait mechanics. Take heart, my dressage riders, now is the time to focus on the quality of gaits. Spending time in diminished gaits does not rob the horse of its innate talents and athleticism. It allows us to rebuild him without the punishing effects of gravity.

If adjusting the impact of ground reaction forces allows us to rebuild our equine athletes, we might also consider how to modulate them in our everyday riding in order to avoid repetitive stress injuries. Consider the weight of the horse, your own weight and tack, the speeds you most often ride at, your training surfaces. All these things increase the impact on each limb. This is further validation for keeping variety in your training, schooling at various speeds, and occasionally slowing way down.

If you would like to read more of the research, go here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7915051/