Exercise Recommendations for Horses with Myofibrillar Myopathy

Management of Warmblood horses with myofibrillar myopathy (MFM) starts with a ration evaluation and revision, often with the recommendation to include MFM Pellet and Nano-Q10. Another important aspect of management is provision of thoughtful exercise. Consistent exercise increases turnover of structural proteins, which strengthens muscle, and builds enzymes needed to burn energy as fuel.

Although specific recommendations are impossible given the individual expression of the disease among horses, general guidelines have been provided by Stephanie Valberg, D.V.M., Ph.D., a leading authority on the disease.^*

• Schedule. Horses with MFM often require regular days off from training. This is contrary to management strategies for other muscle diseases, such as recurrent exertional rhabdomyolysis or polysaccharide storage myopathy 1, in which everyday exercise is often indicated to prevent tying-up. The number of days off per week for MFM horses varies depending on the individual, but several owners of horses with MFM have reported that three days of training followed by two days off works well. Determining what works best for each horse will likely require trial and error.
• Warm-up. An appropriate warm-up period for most horses with MFM is beneficial. A 10- to 15-minute session on the longe line is one way to encourage relaxation and low-level collection in which the horse begins to raise the base of the neck, engage the abdominal muscles, and lift the back. Extreme engagement of the hindquarters is not the objective of the warm-up period. Artificial aids that are adjusted to promote a long, low frame (seek professional assistance if necessary) include Vienna reins or neck-stretchers and are favored over side reins. Most of the work should be at the walk and trot during the warm-up, though short stints of canter are acceptable.
• Ridden work. Long and low work should continue under saddle after the warm-up at all gaits with plenty of attention paid to the walk and trot. Periods of relaxation should be intermingled with periods of collection. Prolonged periods of collection—more than 5 minutes—should be avoided. To strengthen the abdominal muscles, hill work, poles, and cavaletti can be introduced gradually. Anecdotal evidence suggests that ride times between 30 and 45 minutes seem to be most productive. Horses coming back to work should have shorter ride times in the beginning of their reconditioning and then progress to longer rides.
• Turnout. Confinement can be detrimental to horses with MFM, especially prolonged confinement, so turnout is important. As much daily turnout as possible is recommended, and the paddock or pasture should be large enough to allow horses to move freely at all gaits. Circumstances can complicate turnout schedules (weather, injuries), but every effort should be made to remove horses from confinement daily, even if this means hand-walking or time spent on a mechanical walker or treadmill for 10-30 minutes.

Use these guidelines as a jumping-off point. Consultation with a veterinarian well versed in myopathies as well as  your horse’s diagnosis and idiosyncrasies is always a wise move.

A diagnosis of MFM is made by identifying aggregates of a cytoskeletal protein called desmin in a muscle biopsy using immunohistochemical stains. To learn more about submitting a muscle biopsy for diagnosis, go to the Valberg Neuromuscular Diagnostic Laboratory.

^*Valberg, S.J. 2021. Diagnosis and management of myofibrillar myopathy in Warmblood performance horses. In: Proc. American Association of Equine Practitioners 67:214-218.