If your horse suddenly becomes stiff, painful, or unwilling to move during or after exercise, you may hear someone say they are “tying up.”
But what exactly does that mean?
Tying up is the common name for exertional rhabdomyolysis, a condition involving damage to skeletal muscle cells. Episodes can range from relatively mild muscle soreness and stiffness to a serious medical situation requiring immediate veterinary care.
And while some horses may experience a single episode after unusually strenuous exercise, others repeatedly tie up because of an underlying muscle disorder such as Polysaccharide Storage Myopathy (PSSM).
Understanding why your horse is tying up is an important first step toward helping them feel and perform their best.
What Does Tying Up Look Like in Horses?
Signs can appear during exercise, shortly after exercise, or occasionally even without strenuous activity.
A horse that is tying up may show:
- Sudden muscle stiffness or cramping
- Reluctance or refusal to move
- Short, stiff steps
- Muscle trembling or twitching
- Excessive sweating
- Painful or firm muscles, particularly over the hindquarters
- Rapid breathing or elevated heart rate
- Poor performance or exercise intolerance
- Weakness
- Dark brown or coffee-colored urine in more severe cases
Some horses show much subtler signs.
You may notice a horse that simply doesn't want to move forward, seems unusually tight through the back or hindquarters, avoids difficult stops or turns, struggles to collect, or isn't performing like they normally do.
Repeated episodes of unexplained muscle soreness or stiffness deserve a closer look.
Why Do Horses Tie Up?
There isn't one single cause of tying up.
A horse with no previous history may experience a sporadic episode after exercise that exceeds their current level of conditioning. Dehydration, electrolyte imbalances, illness, nutritional deficiencies, heat, and other management factors may also contribute.
Other horses experience recurrent tying up, meaning episodes happen repeatedly even when the workload doesn't appear excessive.
In those cases, your veterinarian may investigate underlying muscle disorders such as:
- Polysaccharide Storage Myopathy Type 1 (PSSM1)
- Polysaccharide Storage Myopathy Type 2 (PSSM2)
- Recurrent Exertional Rhabdomyolysis (RER)
- Other metabolic or muscular conditions
Bloodwork measuring muscle enzymes such as CK and AST can help determine whether muscle damage has occurred. Depending on your horse's history and breed, genetic testing or a muscle biopsy may also be recommended.
What Is PSSM?
Polysaccharide Storage Myopathy, or PSSM, is a muscle disorder involving abnormal glycogen storage within skeletal muscle.
Glycogen is the stored form of glucose that muscles use as an energy source.
Horses affected by PSSM can experience:
- Muscle pain
- Cramping
- Stiffness
- Weakness
- Exercise intolerance
- Reluctance to move
- Episodes of tying up
PSSM Type 1
PSSM1 is caused by a mutation in the GYS1 gene, which affects glycogen production and causes excessive or abnormal glycogen accumulation in skeletal muscle.
The mutation has been identified in numerous breeds, including Quarter Horses and related breeds, draft breeds, Morgans, Tennessee Walking Horses, and others.
PSSM1 can be identified through genetic testing using blood or hair samples.
PSSM Type 2
PSSM2 describes horses that demonstrate abnormal glycogen storage in muscle but do not carry the GYS1 mutation associated with PSSM1.
Unlike PSSM1, there is currently no scientifically validated DNA test identifying a causative mutation for PSSM2. Diagnosis may involve clinical history, bloodwork, muscle biopsy, and evaluation by a veterinarian familiar with equine muscle disorders.
Because several different muscle conditions can produce similar symptoms, testing can be especially valuable in a horse that repeatedly ties up.
What Should You Do When a Horse Ties Up?
If you suspect your horse is actively tying up, stop exercising them and contact your veterinarian.
Do not try to “walk it off” or force a painful horse to continue moving.
Depending on the severity of the episode, veterinary treatment may include pain management, fluids, correction of electrolyte or metabolic abnormalities, and bloodwork to assess muscle damage.
Provide access to fresh water and keep the horse somewhere safe and comfortable while following your veterinarian's instructions.
Dark or coffee-colored urine is particularly concerning.
When muscle cells are severely damaged, they can release a protein called myoglobin into the bloodstream. Myoglobin is filtered through the kidneys and, in significant amounts, can contribute to kidney damage.
This is one reason severe tying-up episodes should never be treated as simple post-workout soreness.
Supporting a Horse Prone to Tying Up
Once the immediate episode has passed, the bigger question becomes:
Why did it happen?
Long-term management will depend on the underlying cause.
Your veterinarian may recommend evaluating:
Diet
Horses with certain muscle disorders, particularly PSSM1, often benefit from careful control of dietary sugar and starch.
Rather than focusing exclusively on grain, evaluate the entire diet—including forage, pasture, concentrates, treats, and supplements.
Consistent Exercise
Regular, appropriately conditioned exercise can be extremely important for many horses prone to recurrent tying up.
Sudden changes in workload or asking an under-conditioned horse for intense exercise may increase risk.
For horses diagnosed with PSSM, exercise and turnout recommendations should be developed with your veterinarian based on the individual horse.
Hydration and Electrolytes
Muscles depend on proper hydration and electrolyte balance to function normally.
Horses working heavily, sweating significantly, traveling, or exercising in hot weather may require additional attention to water and electrolyte intake.
Recovery
Don't ignore repeated stiffness simply because your horse “works out of it.”
Chronic soreness, tight muscles, reluctance to perform certain movements, or recurring episodes of tying up may signal an underlying problem that deserves investigation.
Where Does Kidney Support Fit?
The muscles and urinary system play different roles in the body, but they become closely connected when significant muscle damage occurs.
As damaged muscle cells release substances such as myoglobin into circulation, the kidneys are responsible for filtering those substances from the bloodstream.
That makes normal hydration, urinary function, and kidney function particularly important for exercising horses and during recovery.
Silver Lining Herbs Kidney Support is formulated to nutritionally support:
- Normal kidney and bladder function
- Healthy fluid balance throughout the body
- Normal urinary function
- Exercising muscles and performance
- Horses experiencing occasional muscle tightness or soreness
The herbal blend includes ingredients such as dandelion, juniper berry, parsley, marshmallow, chamomile, kelp, garlic, hydrangea, barberry, and uva ursi.
Kidney Support is intended as nutritional support and should not replace veterinary diagnosis or treatment for a horse experiencing an active tying-up episode, kidney disease, urinary infection, or another medical condition.
Can Tying Up Be Prevented?
Not every episode can be prevented, particularly when an underlying genetic muscle disorder is involved.
However, good management can make a significant difference.
Focus on:
- Consistent conditioning
- Avoiding sudden increases in workload
- Appropriate hydration
- Balanced electrolytes
- A diet suited to your horse's individual metabolic needs
- Regular turnout and movement when appropriate
- Paying attention to recurring muscle soreness or performance changes
For horses with diagnosed PSSM or recurrent exertional rhabdomyolysis, work with your veterinarian to develop an individualized feeding and exercise program.
Don't Ignore a Horse Who Suddenly Feels “Tight”
A horse that becomes unusually stiff, painful, or reluctant to move is communicating that something isn't right.
Sometimes tying up is triggered by a one-time combination of exercise, conditioning, hydration, or nutrition.
Other times, recurring episodes are the clue that leads to the diagnosis of an underlying muscle condition like PSSM.
Either way, recognizing the early signs and supporting your horse's muscles, hydration, urinary system, diet, and overall recovery can help you make better decisions about their long-term health and performance.