Pet Columns, Office of Public Engagement, College of Veterinary Medicine at the University of Illinois at Urbana-Champaign

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Many Horses Don't Like Mondays


Pet Column for the week of January 8, 2001


Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
By Carrie Gustavson
Information Specialist

If your New Year's resolution is to hit the gym and start using muscles you forgot you had, you may soon experience the same painful muscle cramps that some horses get. It's called "Monday morning sickness," "tying up," "recurrent myositis," or "exertional rhabdomyolysis." But no matter what it's called, what it means to a horse is rock-hard, extremely painfully cramped muscles.

"Think about a 'Charlie horse' that has been going on continually for hours or days and you can understand how a horse feels," says Dr. Thomas Goetz, equine veterinarian at the University of Illinois Veterinary Teaching Hospital in Urbana.

"It is often difficult to figure out the exact cause of the cramping," says Dr. Goetz. But typically, this condition occurs in a working horse, endurance horse, event horse, or racehorse that is given a day off to rest. Historically that day was Sunday, so on Monday when put back to work the horse would experience painful leg cramps and typically not want to move.

"Cramps can happen after or during exercise. Some horses only have it once, and others may have recurrent problems," says Dr. Goetz.

You'll recognize an episode of acute cramping by the horse's increased heart rate and respiratory rate and rock-hard lower back, loin, rump, and hamstring muscles. Just as you might walk funny after a hard workout that made your muscles sore, the horse may move with short strides or may not be able to move at all. With the chronic form of the disease, horses often appear clinically normal, but may have very slight to moderate decreases in athletic performance.

To diagnose a horse with this condition, a veterinarian will want to rule out hypothyroidism, laminitis, pleuritis, and colic. A pre- and post-exercise blood test to measure levels of two muscle-specific enzymes, creatine kinase and aspartate aminotransferase, often confirms the diagnosis. Elevated levels of these muscle enzymes indicate significant muscle damage.

"For acute attacks we treat horses with analgesics, sedatives, vasodilators, and muscle relaxants," says Dr. Goetz. "But if the cramping is severe, muscle degeneration can result in myoglobin -- or muscle protein -- release into the urine. Myoglobin is toxic to the kidney and can cause acute renal failure and death. Severely affected horses will need intravenous fluids to help flush the kidneys and to correct electrolyte and acid/base abnormalities."

Many factors seem to contribute to recurrent problems and several treatments show promise. Decreasing the quantity of grain fed and feeding greater quantities of high quality hay can be beneficial. Regular, not intermittent, exercise is also important.

Dimethyl glycine (DMG) is an amino acid thought to improve muscle utilization of oxygen and has been useful for some horses with recurrent cramping. Feeding balanced electrolytes such as potassium, calcium, sodium, and magnesium may improve muscle function. B complex vitamins, vitamin E, and selenium are effective supplements in some horses.

Besides diet changes and supplementation, rest is typically recommended the horse's muscle enzymes return to normal.

For more information about recurrent myositis, contact your local equine veterinarian.