09/09/2025
That pesky fly twitch muscle
We often obsess over fascial lines or the deep fascia yet the fascial sheets are not discussed as much and considering how superficial yet often reach much deeper and how much they cover, and how we can influence the superficial structures by touch, pressure yet we often think of superficial as somewhat inferior to deep yet all matters in the whole horse, the senses are the first mountain we must climb to ever to be able to affect those deeper structures and yet the visual clues that the superficial reveals tells us a story of what may be going on in those areas we cannot see
We have all seen our horses twitch their skin if a fly lands on them and often followed by a tail swish and a quick whip round with their head if the muscle doesn't dislodge the offending critter and that’s great that muscle is doing exactly what it is designed to do and why often we call it the fly twitch muscle rather than the term you may hear your therapist use eg. subcutaneous trunci etc etc etc (the latter part of the name will change depending on where the muscle is covering the body)
I have done a post before about this muscle because when over reactive it can cause a few issues so thought I would revisit it again
So what is it, what does It do and how this muscle can indicate other things that may be going on
Sub cutaneous means beneath the skin so we class this as a superficial muscle but it is deep enough that it should not for the most part be visible to the eye but at some times of the year it will become more visible and you will see this as a wavy line throughout certain parts of the body and again from neck to behind the last ribs
There are different latter names for where it is present in the body (see pic) and we have the subcutaneous, fasciae, coli, Omobrachialis, trunci, and superficial trunk fascia has to be included (This will enclose the subcutaneous trunci, now think of where it is and what structures will it affect )
It is a thin striated (can contract and relax independly) muscle
Fun fact in some humans we have the remnants of this muscle, on our forehead, scalp, platysma in the neck and other areas)
It is also referred to as the panniculus carnosus (panniculus derived from the Latin word cloth and carnosus derived from the Latin word flesh) it is a reflex that acts upon stimulation to the skin from the cutaneous nerves which are derived from spinal nerves, in simple terms it’s a reflex response which the horse has no control over it acts automatically when irritated, your vet may try to illicit this response when assessing neurological issues along the spine, it is super important in relation to the superficial fascial system and it makes sense for if the area becomes over reactive and the connection to the fascia are we going to lose some of the function of the skins ability to glide correctly (only my thoughts no proof lol)
It's so important we understand the action of the reflex response especially as we manipulate it so much only when the irritant has not gone with the horse make the conscious effort to get rid of it, food for thought if your horse is kicking out
Usually the reason we get called out is because often the horses have become "girthy" rather than the owner seeing that tell tale wiggly line along the body mostly they will recognise a reluctance to girth, headshaking when touched on the neck, a reluctance to stride under with the hind end, and so on and I guarantee you these calls will come in all at the same times of the year and 9 times out of 10 most of these horses have been diagnosed with ulcers or they have a sensitivity to the changes in grasses or other skin sensitivity issues etc. (mostly I will also see that tell tale swollen parotid gland Aswell)
Most of the horses that I come across are also maybe classed as nervous or sensitive but again gut brain relation works both ways each will affect the other often I see this a lot on a new horse in a new environment that may be a little worried about change
Imbalances and overworking or underworking in some areas can make this muscle visible if you see it in the neck it could mean an issue around the front end and if you see it visible around the edge of the ribs it may be a hind end issue so correct balance when working is so important so the horses body can work in harmony but we must remember internal and external and whole horse
Dehydration can also be a cause of why it becomes visible, but I don't see this often
And we have to put things into context if your horse has been out all day in the sun and there are lots of flies and insects about then of course you may see this more visible or If your horse has just moved to a new place and undergoing more work etc again you may see it more visible as always we have to look at the bigger picture and mostly if we can't explain why then we need to look further as to the why for example if this is visible throughout all the year then what is going on for us to see something which sits in the deep layer of the skin
When you see which muscles can be affected (and this is only a few) you can understand why maybe your horse is not a happy bunny at some points of the year, just look at how much the girth will cover an area of affected tissue,
I do not work softly on these horses as it can be super irritating, even placing the lead rope over the neck can irritate them, I mostly use myofascial release of long holds of compress and stretch but like I say if the horse then goes out and there are lots of flies etc we usually only offer temporary relief it's how long this is present I more focus on
Again, this is only my view through the years of working on horses and I am giving you my thoughts as to what I correlate but for me It makes sense if you look at the two pictures and merge them together are these not the area's most horses have at certain times of the year??
