Horse muscular disorders can have serious consequences for both health and performance. Muscles are necessary for movement, balance, and stability, and any muscular loss or dysfunction can result in a deterioration in the horse’s performance and living conditions.
How does the horse’s muscular system work? What are the different muscular disorders and what are their causes and consequences?
Muscle anatomy & physiology
To better understand muscular disorders in athletic horses, it is essential to be aware of a few basics:
Skeletal muscle characteristics
Skeletal muscles are the main muscles involved in body movement. They are attached to the bones by tendons and are controlled by the nervous system. They are made up of muscle fibres that are surrounded by fascia, which is a type of connective tissue.
These muscles are specially developed in the horse’s limbs, back, and buttocks. The muscles of the front limb include the biceps brachii, triceps brachii and deltoid. Those of the hind limb include the quadriceps femoris, gluteus maximus and gastrocnemius. Along the back, the muscles supporting the spine are the longissimus thoracic, iliocostalis and spinalis. These muscles are essential for the stability and flexibility of the spine.
Muscle function
Muscles are made up of two kinds of fibres: type I and type II. Type I muscle fibres, often known as slow muscle fibres, are best suited to low-intensity but long-duration exercises like walking and trotting. Type II muscle fibres, often known as fast muscle fibres, are best suited for high-intensity, short-duration exercises like galloping and jumping.
When a muscle contracts, the neurological system stimulates the muscle fibres, resulting in a pulling force. This force is transferred to the tendons, which are linked to the bones and move. The amount of force produced is determined by the number of muscle fibres involved and the velocity at which they contract. Because of their size and high contraction, the skeletal muscles of the athletic horse are capable of exerting huge forces.
Muscular disorders causes
What are the potential causes?
Excessive exercise is one of the main causes of muscle disease in the horse athlete. Over-exercising or inappropriate training can lead to excessive muscle fatigue, injury and/or inflammation. Overuse can potentially permanently injure muscles, resulting in decreased performance and an increased chance of injury.
Muscle trauma, such as bruising and strains, are also common causes of muscle disease in horses. They can be caused by a direct impact, falls or training-related injuries. Muscle damage can lead to pain, inflammation and reduced muscle function.
Muscle pathology can also be caused by nutritional deficiencies. Protein, mineral, and vitamin deficits can have an impact on muscle health, leading to tiredness and increased susceptibility to muscle injury. These imbalances can also impair the body’s ability to recover from exercise, increasing the risk of muscular damage.
Some metabolic disorders can also play a role in the development of muscular diseases. Cushing’s syndrome, equine metabolic syndrome and periodic hyperkalaemia are examples of disorders that can affect muscle health.
What are the risk factors?
Overuse is a common risk factor associated with muscle disease in the athletic horse. It can be caused by overtraining, frequent competition or fast changes in training intensity. This can lead to muscle damage, tears, tendonitis and muscle pain. The muscles most often affected by overuse are the muscles of the hind limbs, particularly the buttocks and thigh muscles.
Lack of recovery is also a factor, as are muscle imbalances. These can be caused by poor posture, repetitive movements, previous muscle damage or a lack of balanced muscle strengthening.
Finally, inadequate nutrition can lead to weight loss, loss of muscle mass, decreased muscle strength and reduced athletic performance. Protein, vitamin E, selenium, and electrolytes are the most prevalent nutritional deficits that can contribute to muscle illness. Nutritional deficiencies can also contribute to glucose excess, which can lead to glycogen storage myopathy (PSSM).
Typology of muscular disorders
Muscle illnesses in horses can be divided into several categories based on their cause and clinical manifestation:
– Glycogen storage myopathies (or PSSM) are genetic muscle disorders characterised by abnormal storage of glycogen (Substance stored in the liver and muscles, forming a glucose reserve for the body) in the muscles. Muscle weakness, tiredness, stiffness, muscular atrophy, and discomfort are all clinical signs. Horses with this syndrome are frequently more sensitive to exercise and may have more significant muscle weakness following exercise.
– Myositis, also known as rhabdomyolysis, is an acute muscle condition caused by sustained high muscular exertion that results in the rupture of muscle cells and the release of myoglobin into the bloodstream. Muscle weakness, discomfort, black urine, kidney failure, and fever are among the clinical signs. Horses suffering from this illness may find it difficult to stand or move normally.
– Atypical equine myositis (AEM) is a severe and potentially fatal muscle illness caused by toxin poisoning from soil bacteria Clostridium sordellii and Clostridium novyi. Muscle weakness, stiffness, incoordination, lack of appetite, and kidney failure are among the clinical signs. MEA is frequently linked to the ingestion of Clostridium spore-contaminated alfalfa hay.
– Muscle contractures are conditions characterised by prolonged or continuous muscle contraction that can be painful and restrict normal movement. Muscle spasms can be caused by a variety of factors, including excessive muscular effort, dehydration, muscle injury or electrolyte imbalance.
Diagnosis, treatment & prevention
Diagnosis
Muscle issues in equine athletes can be difficult to diagnose because the symptoms can be similar to other musculoskeletal illnesses. A mix of clinical, imaging and laboratory investigations is used to make a diagnosis.
The clinical examination is the first step in the diagnosis and consists of an assessment of the horse’s symptoms and general physical condition. Imaging methods, such as ultrasound, X-ray and MRI, can help diagnose muscle pathology. Finally, laboratory tests, such as blood and urine analysis, can help identify abnormalities in electrolyte, protein and muscle enzyme levels, which may indicate muscle pathology.
Treatment
Muscle disorders in athletic horses are treated differently depending on the kind and degree of the disorder. Rest is frequently advised for mild to moderate muscle problems. This helps the muscle to naturally recover and repair.
Nonsteroidal anti-inflammatory medicines (NSAIDs) and physical treatment, such as massage therapy, ultrasound, and shock waves, can be used to reduce the pain and inflammation linked with muscular disorders. These techniques can help relieve discomfort, increase blood flow, and enhance muscle repair. Surgery may be required in severe cases, such as to heal muscle tears or rectify muscular abnormalities.
Muscular disorders prevention
Muscle disease prevention in athletic horses is critical to reducing the risk of injury and maintaining peak performance.
Regular training tailored to each horse can help strengthen muscles and reduce the risk of injury. Performance monitoring tools such as EQUIMETRE VET are a valuable aid in managing and individualising training.
To learn about a concrete case, we suggest you read the story of Arion. His trainer was able to prevent potential myositis by analysing the recovery data.
A gradual warm-up and stretching can also help to reduce muscular stiffness and prevent muscle damage at work. Finally, a well-balanced diet rich in protein, vitamins, and minerals is essential for sustaining muscular health.
Conclusion
Muscular diseases are common in athletic horses, particularly those competing in equestrian disciplines that involve a lot of physical effort. Technological and scientific advancements now provide more effective and timely methods for detecting muscle injury, thereby improving horse health and performance.
Cependant, la recherche continue dans ce domaine et offre des perspectives prometteuses pour améliorer la compréhension des pathologies musculaires chez les chevaux athlètes et développer des traitements plus efficaces, tels que l’utilisation de cellules souches et de thérapies géniques.
SOURCES :
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Findley, J. and Singer, E. (2015). Equine back disorders 1. Clinical presentation, investigation and diagnosis. In Practice, 37(9), pp.456–467. doi:https://doi.org/10.1136/inp.h4854.
Quist, E.M., Dougherty, J.J., Chaffin, M.K. and Porter, B.F. (2011). Diagnostic Exercise: Equine Rhabdomyolysis. Veterinary Pathology, 48(6), pp.E52–E59. doi:https://doi.org/10.1177/0300985811414034.
Keywords: equine muscle pathologies, muscle system, quantification tool, equine physiology, equine locomotion, EnvA, CIRALE