Many of us are familiar with the application of bell boots in our equine athletes. English and Western disciplines alike apply bell boots on their athletes to prevent overreaching. Bell boots provide our horses with protection, but recent research reveals that the application of bell boots can actually correct muscle asymmetries in our equine athletes too!
Today, in our #ScienceIsSuper blog we discuss an article published in the Journal of Equine Veterinary Science that explores the role of proprioceptive signals in our horse's lower legs, by having them wear bell boots. The biomechanics team at the University of Copenhagen studied how the application of bell boots helped 8 non-lame horses (yes, there is such a thing as healthy non-lame horses, folks! lol) build a stronger superficial gluteal muscle over the course of 6 weeks.
The scientists out there might be wondering, but how were they able to measure the progression of the SupGlut muscle function over the course of 6 weeks?...
...by LISTENING to the muscles of course! Yep, you *heard* me right, using Acoustic Myography (AMG), which assesses muscle function by recording the sounds of the contracting muscle, they measured the changes in the SupGlut tissues.
"Do not listen with the intent to reply, but with the intent to understand"
- Your Friendly Acoustic Myography Machine, June 2019
Okay, so this amazing group of scientists curated an experiment, using AMG technology to measure changes in the SupGlut. What did they do?
They took a page out of Dr. Hilary Clayton's book, who found that "light-weight chains stimulated the cutaneous mechanoreceptors in the coronet & pastern with a positive effect on the swing phase of each stride" (Jensen et al 2018). Please note, cutaneous is anatomy talk for skin. And a mechanoreceptor is a sensory receptor that responds to pressure/sensation of touch, just like a taste bud on the tongue detects taste, these bad boys detect mechanical sensations. So basically, this study used bell boots as stimuli to activate their mechanoreceptors, and measured the changes over time in the SupGlut using AMG. For comparison sake, the weight of the bell boot on a horse's fetlock, equates to the weight of a single sheet of A4 paper on a human! #SensitiveMuch
(P.S. Anything developed/written by Dr. Clayton is incredible, she is a leader in equine biomechanics research. Her work has literally been described as biomechanics brilliance. So there's that, look her up!)
For this study, they used eight healthy horses, six geldings and two mares between the ages of 6 and 15 years old. They were walked, trotted, cantered, in left hand and right hand circles. All of the horses were evaluated prior to the study, and were vetted as sound with no previous injuries. After evaluating their movements, they deciphered which hindlimb was weaker, to know which hindlimb to put the bell boot on, and in this case the weaker hindlimb was the one that exhibited a higher ESTi score obtained from the AMG.
Real quick. What is an ESTi score?
ESTi is what the AMG records. The goal is to have low ESTi values. An ESTi score provides an overview on the muscle haps. Haps is a colloquial term for "happenings".
E is for efficiency - determines how long the muscle is "on" (time)
S is for spatial - reflects the recruitment of motor units (amplitude)
T is for temporal - measures how fast the motor units are firing (frequency)
The neat thing about ESTi is that the mean score of E+S+T can be combined to give you a general idea of muscle function, but when you find a different value, you can dig deeper and see what aspect of the muscle is not functioning efficiently, i.e. Is it lack of motor units? Is it a result of slow motor units?
...science...am I right? *heart eyes emoji*
Back to the experiment, over the course of six weeks, training with the bell boot on the weaker hindlimb occurred every 3 days at 60 minute intervals with regular exercise. The riding was done by each horse's respective owner, and the bell boot was not placed on the hindlimb for consecutive days in a row to avoid habituation, and was only applied every third day. So, are you on the edge of your seat, waiting to hear what this study revealed? ME TOO!
Okay, now obviously I wouldn't share this study if it didn't exhibit some sort of positive correlation....so yes, they found a positive effect on hindlimb imbalance after bell boot application/induced proprioceptive activation, now whether that can be maintained for a longer period of time still remains to be seen...but you guys this piece of paper bell boot activated mechanoreceptors and effected changes. That's some cool sh** though, right!?
I won't get into the nitty gritty results, you can read the tables and radar plots yourself in the paper, but to summarize they found that the AMG data was a great way to measure muscle changes (you go, ESTi!). The study showed that in a left-hand circle weak SupGluts became more engaged, and the imbalances reduced to the point of being nonsignificant, with low ESTi scores babyyy. They found increased fibre activation and more intense fibre activity in the initially weak hindlimb muscles, thus showing more coordination post-boot. There was a slight contradiction (for lack of a better word?), where in the right-hand circle, they found a worsening of left hind limb engagement at the canter, researchers attributed this change to overcompensatory mechanisms at play. More research is certainly needed to further investigate these results. What about applying this study to lame horses? Or to a different discipline of horses? Or under different variables? The possibilities are endless, the bank account for research is not, unfortunately ;
So, what are the implications of this study? Why should we care about this, as professionals and as horse owners? Well, for me, a professional in the equine health and wellness industry, compensatory mechanisms and weight distributing tendencies in our equine athletes are LITERALLY the worst. Compensation can result in repetitive strain injuries or overloading of certain bones, ligaments, tendons and muscles. These imbalances, which are yes normal to find in any hard working athlete that may fatigue and compensate...but ultimately are what we at Vitality Equine work to improve EVERY DAY. Vitality Equine supports anti-imbalance, and pro-balance in equine athletes. To improve performance and prevent injury, muscle imbalances must be corrected! Ultimately, those pesky imbalances lead to compensatory injury, and lameness. So, you see why this study is exciting? It's another tool that us professionals and owners can use to help our athletes better achieve muscular balance and symmetry.
The moral of the story is that a balanced equine athlete is essential.
So, ask your equine health professional how you can better balance your athlete. As they say...
"Balanced Horse, Happy Life"
Clayton HM, White AD, Kaiser LJ, Nauwelaerts S, Lavagnino M, Stubbs NC (2010). Hindlimb response to tactile stimulation of the pastern and coronet. Equine Veterinary Journals ;42:227e33.
Jensen, A-M., et al., (2018) The Efficacy of Intermittent Long-term Bell Boot Application for the Correction of Muscle Asymmetry in Equine Subjects. Journal of Equine Veterinary Science, (68) 73-80.