Published: 19 Feb 2019 | Last Updated: 18 Jan 2024 15:44:26

Recurrent exertional rhabdomyolysis (RER) in horses is an exercise-associated disease that involves repeated episodes of muscle damage.

The disorder is also sometimes known as tying up, azoturia, setfast, monday-morning disease or just rhabdomyolysis. The disease can be recognised by the clinical signs (which vary in severity) but can include muscle spasms or muscle trembling, stiffness or hard muscles, high heart rate, sweating, muscle pain, reluctance to move or recumbency, red-brown urine (myoglobinuria) and in severe cases even death. Often a vet will confirm the diagnosis with a blood sample and sometimes also a muscle biopsy sample.

Connemara pony - one of the breeds this study is looking at

Whilst there appears to be a genetic component to many forms of RER, the gene or genes causing the disease have not yet been identified. There is also currently no cure for this disorder although many horses can continue to perform well if managed appropriately. The disorder is often recognised in racing Thoroughbreds, but a variety of other breeds are also diagnosed with RER.

Researchers at the RVC are investigating the genetics of exertional rhabdomyolysis in horses to identify predisposing genetic risk factors and possible novel therapeutic targets. It is thought that the severity of the clinical signs seen in RER cases might be associated with different specific genetic changes, and it is hoped that specific patterns of clinical signs can be identified in these different breeds that might be associated with some of these genetic changes.

Most relevant research so far has been done in Thoroughbreds, but the new study will look at other breeds popular in the UK - specifically warmblood horses and Connemara ponies.

The study will look at samples from two sets of horses/ponies in the UK

  • warmblood horses and fully registered Connemara ponies over the age of 8 with no history of tying-up or other muscle-related diseases. These animals will be control subjects and they are an important part of the study
  • Breeds as above, that have tied-up with exercise, at least twice – confirmed by blood testing by a vet.

A hair sample  (for DNA testing) will need to be taken, and owners will be asked to complete a questionnaire regarding each horse’s diet, exercise regime, breeding and clinical history in order to dissect genetic, lifestyle and environmental factors. The results of this profile will be shared with the owner.

Collection of DNA will be completely non-invasive and the sample will be used for research purposes only.

The study has received ethical approval from the RVC Clinical Research Ethical Review Board (CRERB) and Social Science Research Ethical Review Board (SSRERB) and assigned the following unique numbers: 2018 1834-2 (CRERB) and SR2018-1799 (SSRERB).

This study is entirely voluntary and participants are free to withdraw at any time without giving reason. Any identifying data provided will be securely stored according to the Data Protection Act and GDPR principles and any data presented or published will be completely anonymised so that there is no way that participating owners, horses or vets can be identified.

Participants can opt in to receive the personality profile of their horse, as analysed by the personality section of the questionnaire, and/or receive an invitation to an evening lecture event (to be arranged in winter 2019) at the Hawkshead RVC campus.

SupervisorsDr Androniki Psifidi and Professor Richard Piercy


If you would like to find out more or get involved then please email

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