Your horse seems fine one minute, then suddenly stiff, sweaty, and refusing to move. It’s not laziness. It’s not attitude. It could be tying up. 

This painful muscle condition can hit without warning, especially after exercise. Some horses show mild signs. Others are left trembling in agony. 

It can look scary, and if you don’t know what’s happening, it’s easy to panic. But here’s the good news: with the right care and a few smart changes, most horses bounce back. 

In this guide, we’ll break down what causes it, how to spot it, and what you can do.

What is Tying Up in Horses?

Tying up is a painful muscle disorder in horses, also known as exertional rhabdomyolysis. It happens when muscle fibers break down during or after exercise. 

This leads to muscle stiffness, cramps, and sometimes dark-colored urine caused by muscle proteins leaking into the bloodstream.

The condition mostly affects the large muscles in the hindquarters. Some horses freeze in place, reluctant to walk. 

Others may sweat heavily and seem distressed. While it can happen suddenly, certain horses are more prone, especially those with poor conditioning, high-carb diets, or genetic muscle conditions like PSSM or RER.

Tying up can be a one-time event or a chronic issue. Either way, it’s serious and needs quick attention

Common Names of Tying Up

Tying up in horses is known by several other names, reflecting its history and the various contexts in which it occurs. Understanding these terms can help in recognizing and discussing the condition:

Azoturia. An older term, used to describe severe cases of muscle stiffness and cramping in horses.

Monday Morning Disease. This name originated from the observation that horses, particularly draft horses, developed symptoms after a day of rest followed by work. 

Set Fast. A colloquial term describing the sudden onset of muscle stiffness, where the horse appears to be “set” in place and unable to move comfortably.

Holiday Disease. Similar to Monday Morning Disease, this term refers to episodes occurring after a period of rest or “holiday,” followed by a return to work. 

Exertional Rhabdomyolysis (ER). The medical term for the condition describing the breakdown of muscle tissue due to exercise. 

Cording Up. A less common term that refers to the hardening or “cording” of muscles during an episode.

These terms are often used interchangeably, but they all describe the same underlying issue. Recognizing the various names can aid in understanding historical references and regional terminology related to this condition.

Types of Rhabdomyolysis

Tying up in horses manifests in various forms, each with distinct causes and management strategies. Here are the types you need to understand for effective prevention and treatment.

1. Sporadic Exertional Rhabdomyolysis (SER)

Sporadic ER occurs infrequently and is typically triggered by external factors such as:

• Overexertion without proper conditioning
• Electrolyte imbalances
• Vitamin E or selenium deficiencies
• Viral infections (e.g., influenza, herpes)

This form can affect any horse, regardless of breed or age, especially when there’s an imbalance between diet and workload.

2. Chronic Exertional Rhabdomyolysis

Chronic ER involves recurrent episodes and is often linked to underlying conditions:

a. Recurrent Exertional Rhabdomyolysis (RER)

Recurrent Exertional Rhabdomyolysis, or RER, mostly affects high-strung breeds like Thoroughbreds and Arabians. The issue starts with how their muscles handle calcium. 

When calcium isn’t regulated properly, muscles cramp and tighten. This can happen during or after exercise. 

It’s painful and upsetting for the horse. Stress, excitement, and uneven training can trigger it. 

To manage RER, horses need regular routines. Reducing stress is also key. With the right care, many horses stay active and comfortable.

b. Polysaccharide Storage Myopathy (PSSM)

PSSM is a genetic disorder causing abnormal sugar storage in muscles, leading to muscle stiffness and pain. It has two types:

Type 1 PSSM:

PSSM is caused by a mutation in the GYS1 gene. This genetic mutation affects how the horse’s muscles store and use glycogen, leading to painful cramping and stiffness after exercise.

It’s most commonly found in Quarter Horses, Draft breeds, and breeds closely related to them. These horses are more likely to experience repeated episodes unless managed carefully.

Type 1 PSSM is diagnosed through genetic testing. A simple DNA test can confirm if a horse carries the mutation, making early diagnosis and management much easier.

Type 2 PSSM:

Type 2 PSSM differs from Type 1 in that it has no identified genetic mutation. The exact cause remains unclear, which makes it more challenging to diagnose and study.

This form is most often seen in Warmbloods, Arabians, and a few other performance breeds. Affected horses may show signs of tying up despite appearing healthy and fit.

Since there’s no genetic marker, diagnosis is usually made through a muscle biopsy. This allows veterinarians to observe abnormal muscle sugar storage patterns under a microscope.

Managing Type 2 PSSM involves feeding a low-starch, high-fat diet and keeping the horse on a consistent exercise routine. 

These changes help stabilize energy metabolism and reduce the risk of muscle episodes.

3. Atypical Myopathy

A rare but often fatal form of rhabdomyolysis, Atypical Myopathy is caused by ingestion of toxins like hypoglycin A found in certain trees (e.g., sycamore maple). 

It leads to rapid muscle breakdown, weakness, and dark urine. Immediate veterinary intervention is critical.

Risk Factors and Causes of Tying Up

Tying up can strike suddenly, but it rarely comes out of nowhere. Some risk factors and underlying causes make some horses more likely to suffer from it than others, include:

1. Overexertion and poor conditioning

Working a horse too hard when it’s not fit can trigger tying up. This is common when horses return to work after time off or are pushed too hard, too soon.

2. Inconsistent exercise routines

Irregular schedules, such as long rest days followed by intense workouts, can shock the muscles and lead to cramps, especially in horses that need daily movement.

3. High-starch, high-sugar diets

Too many grains or sugary feeds can overload the horse’s system. Horses prone to tying up often respond better to low-starch, high-fat diets.

4. Electrolyte imbalance

Sodium, potassium, calcium, and magnesium are essential for muscle function. A lack of these can lead to cramping, especially during hot weather or after sweating heavily.

5. Vitamin deficiencies

Low levels of vitamin E and selenium can increase muscle stiffness and reduce recovery. Horses in selenium-deficient regions are especially at risk.

6. Genetic disorders

Some horses are genetically predisposed. PSSM and RER are two common inherited muscle conditions that cause chronic tying-up episodes.

7. Hormonal and temperament triggers

Hot-tempered or excitable horses are more prone to stress-related tying up. Hormonal changes, especially in mares, can also increase the risk.

8. Cold weather and stall rest

Cold temperatures and restricted movement can make muscles tighter and less flexible, which increases the risk when the horse returns to work.

Signs of Tying Up

Stiffness and reluctance to move.

The horse may suddenly stop walking, especially during or after exercise. It may seem locked up in the hind legs or unwilling to turn.

Tense or hard hindquarter muscles.

The muscles over the rump may feel firm, tight, or hard as a rock. This tension is often painful and makes movement uncomfortable.

Sweating without an obvious cause.

Excessive sweating, even in cool weather or with light work, is a red flag. The sweat is usually due to pain and muscle strain, not effort.

Shaking or muscle tremors.

The horse may tremble, especially in the flanks or hind legs. These involuntary twitches are often signs of muscle fatigue or cramping.

Rapid breathing and elevated heart rate. 

The horse might breathe quickly and look panicked. Even after stopping work, the heart rate stays high longer than normal.

Abnormal stance or posture. 

You may see the horse stretching out its hind legs or standing awkwardly. Some appear “parked out” in an attempt to relieve pressure.

Dark or coffee-colored urine. 

This serious symptom signals muscle breakdown. The dark color comes from myoglobin being released into the bloodstream.

Pain when touched. 

The horse may flinch or pin its ears if you touch the hindquarters. Some even kick out or shift away in discomfort.

Difficulty backing up. 

Backing requires engagement of the hindquarters. Horses tying up will resist or refuse to back, showing pain or stiffness.

Reluctance to pick up a gait. 

The horse may hesitate to trot or canter, or switch gaits abruptly. Transitions become difficult due to sore, tight muscles.

Loss of muscle coordination. 

In extreme cases, the horse may stumble, drag its toes, or seem uncoordinated. This can indicate severe muscle fatigue or early collapse.

What Happens When a Horse Ties Up?

When a horse ties up, its muscles, especially in the hindquarters, cramp, tighten, and break down. It usually happens during or shortly after exercise. 

The horse may suddenly stop moving, sweat heavily, or tremble. Its muscles feel rock-hard, and even small movements can be painful.

Inside the body, the muscle fibers begin to rupture. As they break down, they release proteins like myoglobin into the bloodstream. 

This can overwhelm the kidneys, leading to dark, coffee-colored urine, a serious warning sign.

The horse’s heart rate and breathing often spike, not from effort, but from stress and pain. If the episode is severe and not treated quickly, it can cause lasting damage to the muscles or even kidney failure.

Tying up can be triggered by overexertion, poor conditioning, a high-starch diet, electrolyte imbalance, or genetic disorders like PSSM and RER. 

Whether a one-time event or a recurring issue, it’s painful, dangerous, and needs immediate care.

What to do During an Episode

When a horse starts tying up, every second counts. Here’s what to do immediately:

Stop all activity immediately. Do not push the horse to keep moving. Stop riding or lunging right away. Continuing exercise can make the muscle damage worse.

Keep the horse calm and still. Stress can make the episode more severe. Speak softly, loosen the girth, and keep the horse as relaxed as possible. Don’t force walking, it can cause more damage.

Do not massage or rub the muscles. While it might seem helpful, massaging tight muscles can increase inflammation. Avoid touching the hindquarters unless you’re checking for heat or swelling.

Call your veterinarian immediately. Tying up is a medical emergency. Your vet may administer muscle relaxants, pain relievers, anti-inflammatories, and IV fluids to flush toxins and support kidney function.

Offer small sips of water. Let the horse drink small amounts of cool, clean water. Avoid forcing large amounts too quickly. Add electrolytes if advised by the vet.

Check for dark-colored urine. Observe the horse when it urinates. Dark or coffee-colored urine indicates serious muscle breakdown and a risk to the kidneys. Report this to your vet immediately.

Keep the horse in a quiet, shaded area. Remove the horse from direct sunlight or wind. A quiet stall or shaded paddock can help reduce stress while you wait for the vet.

Don’t offer grain or high-starch feed. Hold off on feeding anything high in sugar or starch. Wait for veterinary guidance before giving any food.

Monitor vital signs. If you’re comfortable doing so, check the horse’s heart rate, breathing rate, and temperature. Share this with your vet when they arrive.

Avoid transporting unless absolutely necessary. Hauling a horse that’s tying up can make things worse. Only load if your vet says it’s safe and absolutely required for treatment.

How to Diagnose Rhabdomyolysis

Here’s how vets confirm the condition:

1. Observation of clinical signs

The first step is recognizing the obvious symptoms: stiff muscles, reluctance to move, sweating, and dark urine. Vets use this initial evaluation to decide if further testing is needed.

2. Blood tests (CK and AST Levels)

Vets will draw blood to check levels of muscle enzymes:

• CK (Creatine Kinase): Rises quickly after muscle damage.
• AST (Aspartate Aminotransferase): Rises slower and stays elevated longer. High levels of these enzymes confirm muscle breakdown is occurring.

3. Urinalysis

Dark-colored urine is tested for myoglobin, a protein released when muscles break down. Myoglobin in the urine confirms severe rhabdomyolysis and helps assess kidney risk.

4. Muscle biopsy

For recurring or unexplained cases, a muscle biopsy can help. It involves taking a small muscle sample and examining it under a microscope. This helps diagnose conditions like PSSM Type 2.

5. Genetic testing

If the vet suspects a hereditary cause, like PSSM Type 1 or RER, they may recommend DNA testing. A simple blood or hair sample can reveal genetic mutations linked to chronic tying up.

6. Rule out other conditions

Vets may also perform additional tests to rule out colic, laminitis, or lameness issues that can mimic tying up symptoms.

How to Treat Tying Up?

Treatment depends on the severity of the episode and whether it’s a one-time event or a chronic problem. Here’s how to treat it step by step:

1. Immediate vet care

If your horse shows signs of tying up, call the vet right away. This isn’t something you can safely treat alone, especially if the horse is in severe pain or has dark-colored urine.

2. Administer anti-inflammatory and pain meds

Your vet may give NSAIDs (like Banamine) or muscle relaxants to ease pain and reduce inflammation. These drugs help the horse relax and recover faster.

See also: How Long Does Banamine Last in a Horse’s Body? 

3. Intravenous (IV) fluids

If muscle breakdown is severe, the vet may start IV fluids to flush toxins like myoglobin out of the kidneys. This reduces the risk of kidney damage.

4. Stall rest with monitoring

Let the horse rest in a calm, cool environment. Avoid movement until the vet says it’s safe. Monitor urine color, behavior, and vital signs.

5. Gradual reintroduction to work

Once cleared by the vet, start slow. Begin with light hand-walking and short rides. Increase workload over weeks, not days, to avoid another episode.

6. Adjust the diet

Switch to a low-starch, high-fat diet. Horses prone to tying up should avoid sugary grains. Add fat sources like rice bran or vegetable oil for energy.

7. Add key supplements

Work with your vet to check for vitamin E, selenium, or magnesium deficiencies. Supplementing these may help reduce muscle stress and cramping.

Management of Rhabdomyolysis

Managing rhabdomyolysis in horses means staying consistent with exercise, reducing stress, and feeding a low-starch, high-fat diet. 

Regular turnout, gradual training, and proper warm-up and cool-down routines help prevent muscle strain. 

Horses prone to tying up may benefit from supplements like vitamin E, selenium, and magnesium, under vet guidance. 

Testing for genetic conditions like PSSM or RER can guide long-term care. Keep the environment calm, use electrolytes in hot weather, and watch for early signs to avoid full-blown episodes.

How to Prevent Tying Up

Preventing tying up starts with a consistent routine. 

Horses do best with regular exercise, not sudden bursts after days off. Daily turnout keeps their muscles active and flexible. 

Diet matters too. A low-starch, high-fat feed is safer than sugary grains and helps support muscle health. 

Always provide clean water, and add electrolytes during hot weather or heavy work. Warm-ups and cool-downs are essential to ease the body in and out of exercise. 

Try to minimize stress by keeping your horse’s schedule calm and predictable. Some horses may also benefit from vitamin E, selenium, or magnesium, your vet can guide you there. 

If episodes continue, testing for genetic conditions like PSSM can reveal what your horse needs. With smart management, most cases are fully preventable.

What to Feed a Horse Prone to Tying Up

Here’s what to focus on when feeding a horse prone to tying up:

1. Low-starch, high-fat diet. Avoid grains and sugary feeds. Instead, choose low-starch commercial feeds or forage-based diets. Energy should come from fat sources like vegetable oil, rice bran, or flaxseed. Fat gives slow-burning energy without spiking blood sugar.

2. Quality forage. Provide free-choice hay or pasture with moderate protein. Forage should be the main part of the diet and can be paired with a ration balancer for nutrients.

3. Vitamin E and selenium. These antioxidants help protect muscle tissue and aid in recovery. If your area is selenium-deficient, a supplement may be necessary, but always consult your vet first to avoid overdose.

4. Magnesium. Some horses prone to tying up benefit from extra magnesium, which supports muscle relaxation and nerve function.

5. Salt and electrolytes. Always provide free-choice salt, and supplement electrolytes during warm weather, heavy work, or travel. This helps prevent dehydration and electrolyte imbalance, a common trigger for tying up.

How Long Does it Take for a Horse to Recover from Tying Up?

Recovery time depends on how severe the episode was. 

For mild cases, where the horse shows only stiffness and no dark urine, recovery can take a few days with rest, hydration, and proper care. Horses may return to light work within a week, but only under a vet’s guidance.

For moderate to severe episodes, especially when muscle breakdown is confirmed through blood tests or the horse shows dark, coffee-colored urine, recovery can take several weeks. 

In these cases, the horse may need stall rest, IV fluids, anti-inflammatory medication, and a gradual return to work.

If tying up is part of a chronic condition like PSSM or RER, recovery becomes long-term management. These horses can still lead active lives, but only with consistent care, dietary changes, and routine exercise.

In all cases, your vet should monitor recovery through follow-up exams or bloodwork.

FAQs

Conclusion 

Tying up is serious, but it doesn’t have to ruin your horse’s life. With the right care, most horses recover and stay active. 

Stick to a steady routine, feed smart, and watch for early signs. Talk to your vet if episodes repeat. 

With good management, your horse can stay strong and comfortable.