Muscle Atrophy – What is it, what to look for and what causes it

Muscle atrophy is something I see a lot of so it seems like a good topic to cover off.

What is it?
Atrophy is a reduction in size of a cell, organ or tissue so, simply put, muscle atrophy is when the muscle shrinks.

What causes it?
Thats where things get more complicated as there are many causes of a muscle deteriorating and reducing in size. Some more common causes are:

  • Ill-fitting tack. This could be the current tack or it could be historic that has left permanent damage
  • Lack of use. This could be in the horse that has changed disciplines, changed work load or has been retired. This could also be as a result of pain which causes the horse to use its body differently so that some muscles over develop and some shrink
  • Medical conditions. There are a couple of conditions that specifically cause muscle wastage or that muscle wastage is a result of the condition.

What does it look like and where is it likely to be seen?

  • White hairs suddenly appearing. This is often the first indication you will see of tack not fitting properly resulting in the hair follicle being damage and colour no longer being produced. Dependant on the location this can be an early sign that you will start to see muscle wastage
  • Hollow behind the wither. This is very common and is indicative of a saddle being too tight at the gullet and constricting the trapezius and latissimus dorsi muscles.
  • Stress line below the wither on the shoulder. A result of the saddle points pinching and the trapezius muscle contracting due to the discomfort.
  • Lack of muscle development over the back. Whilst this can be indicative of a horse needing to do further work to develop its topline it can also indicate a saddle that is too narrow in the channel impacting the longissimus dorsi muscle along each side of the spine.
  • Hollowing on the nasal bone. Whilst not muscle related it is indicative of a noseband that has been repeatedly overtightened causing damage to the delicate nasal structures.
  • Groove behind the ears. Indicative of an incorrectly fitted bridle placing pressure over the poll.
  • Sweeney Shoulder. Damage to the suprascapular nerve in the shoulder blade that results in the muscle deteriorating and the shoulder blade ridge becoming more prominent. This is most often seen in horses that have sudden weight bearing changes or changes in direction such as jumping or polo.
  • Overdevelopment of other muscles. When a horse isn’t carrying itself correctly certain muscles will reduce in size but this will be offset by other muscles becoming overdeveloped. This is commonly seen in horses with the underside of their neck being overdeveloped while the top side of their neck is underdeveloped or their hamstrings are overdeveloped but their back is underdeveloped.

What should you do about it?
As with most things, prevention is better than a cure so the sooner you can notice an issue, the sooner you can correct it before permanent damage is done. A few suggestions would be:

  • Regularly review your horse. If you know what their ‘normal’ is then you will be able to see when things change. Taking photos of your horse from each side on a regular basis is a great way of being able to identify positive and negative changes as when you see your horse every day it can be difficult to see change.
  • Have a qualified saddle fitter and bridle fitter review your horse at least once per year to ensure that tack is still fitting correctly. Your horse is constantly subtly changing shape due to the seasons and workload so your tack fit will alter as well.
  • Work with your trainer/coach to help your horse build muscles in the right places rather than the wrong places.

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