There are many possible causes of stiffness in horses. Older horses often take a little longer to get going, and a heavy training session and the accompanying muscle soreness from the day before can result in it taking a while before your horse warms up. This type of stiffness is relatively easy to remedy by warming up properly, providing some extra supplements, or adjusting your training schedule a bit. It becomes more troublesome if the cause of the stiffness is not so easily determined.

Evaluating Stiffness?

If you pay attention to your horse, you will often notice when your horse moves differently than normal. However, very minor differences are sometimes difficult to see or feel if you see and train your horse daily. Especially when you exclusively ride your own horse and never ride other horses, your horse's way of moving quickly becomes normal for you. This is when stiffness or other movement restrictions "creep in." That's why it can be useful to occasionally ask someone else - your instructor, a stable mate, or the veterinarian - to assess your horse's movements. Especially if you are unsure or have a feeling that something is not quite right.

Check your horse

When grooming your horse, it is good to always run your hand over the large muscle groups of the neck, shoulders, back, loins, and hindquarters. Press the muscles gently; they should be easy to press and quickly bounce back. A horse with high muscle tension, where the muscles feel hard, will also be stiffer during training. By always checking how the muscles feel, you will notice minor changes more quickly. Warm spots on the body are also signals of potential problems.

Tight muscles?

Are your horse's muscles tight? There can be several reasons for this. The most common cause is a magnesium deficiency. This deficiency occurs because there is often insufficient magnesium in roughage in the Netherlands and Belgium. Magnesium is extremely important for muscles. The mineral is directly involved in releasing and relaxing muscle cells after they have contracted (for example, to trot off or jump an obstacle). Muscles must be able to contract but also relax. Otherwise, they will remain permanently in a sort of cramp-like state. This is painful and reduces mobility. Horses that move and train a lot and thus use their muscles more intensively, need more magnesium. Magnesium is best given in a well-absorbable liquid form. This mineral is not only good for muscle cells but also essential for the nervous system, energy supply, and immune system!

Muscle health

In addition to magnesium, vitamin E is also important for muscle health. The effect on large skeletal muscles has been intensively researched. Training causes microscopic damage to muscle fibers, releasing "oxidants". Vitamin E in the muscle tissue ensures that this so-called "oxidative stress" is repaired (this is called the antioxidant effect). The muscle fiber repairs itself and becomes even stronger than before the training that caused the minor damage. This leads to training effect. To facilitate this process, there must be sufficient vitamin E present in the body. The more exertion and muscle work, the higher the requirement. Note: with vitamin E, it is very important to provide the correct form! Many inexpensive supplements contain less absorbable forms of this vitamin, and in horses, it is crucial. The best approach is to feed a liquid supplement that contains the substance RRR-α-tocopherol.

Muscle soreness, 'Monday sickness,' and tying-up

Exercise can lead to muscle soreness. Therefore, ensure enough breaks in the training to clear waste products, and always have your horse cool down properly after a competition. After a heavy training day or competition, it is good to include a day of very light exercise in your training schedule. This way, your horse can "actively recover." As mentioned above, replenishing magnesium and vitamin E is crucial. But other salts or electrolytes may also need to be replenished, especially if your horse has sweated a significant amount. 'Monday sickness' (a form of tying-up) indicates something else. This is a form of stiffness caused by an incorrect feeding regime. The name refers to the old practice when farmers would leave their horses in the stable on Sundays and feed them the same amount of feed as on other days. The horses then received many sugars that they did not expend through heavy work, as they did on weekdays. On Monday, the animals were extremely stiff. Concentrated feed with fast carbohydrates and starch is usually unnecessary for horses doing little or only light work. Always ensure adequate roughage, vitamins, and minerals. A horse with tying-up has tight and hard muscles, stiffness, and often dark urine. In severe cases, call your veterinarian!

Stiffness due to stress

Stress and tension can also cause stiffness in your horse. This is because a horse tenses its muscles and exhibits flight behavior when stressed. Additionally, stress leads to increased magnesium consumption by the body, leaving less for the muscles. In stressful periods such as moving, intense training, a new herd, or starting to break in and saddle up the horse, it may be wise to temporarily give your horse more magnesium. Monitor muscle tension and adjust your feeding and training routines based on your horse's behavior.

Stiffness due to compensation

Several scientific studies in recent years have shown that we, as horse owners, are unfortunately not always good at recognizing slight lameness in our horses. Veterinarians also do not always agree on lameness. This is why more and more technological methods are being developed to measure lameness, including motion sensors and special software. However, these methods are not yet widely used in practice. Moreover, the extent to which a slight asymmetry in a horse's movement is actually bothersome is still unclear. Nonetheless, it is important to understand that most movement problems still stem from the legs. For example, through inflammations or other problems in the joints such as hooves, fetlocks, or knees, but also due to tendon inflammations. A slight lameness in one or more legs will often lead your horse to compensate, making it difficult to notice. Think about how you react when you have a sore knee or ankle. You change how you walk. Ultimately, you might experience back muscle pain. In reality, your back muscles are not the issue, but rather a symptom. This is how it works with horses. Many leg issues go unrecognized but lead to compensatory movements by the horse, sometimes making it seem like the problem stems from a different part of the body. Because muscles often manage compensation, stiffness can be a consequence.

Persistent or recurrent stiffness?

If you've tried everything to solve your horse's stiffness but with no lasting results, there may be more at play than just a muscle issue. When stiffness keeps coming back, despite having a proper feeding approach, training schedule, and supplements in place, it is essential to look further. Together with your veterinarian. Compensation for leg problems is one possibility. X-rays and ultrasound can provide insights into joint disorders or tendon inflammations. However, odd lameness and hard, stiff muscles might also be signs of diseases such as PSSM1 or PSSM2.

Sources:

Carvil, Phil MSc1; Cronin, John PhD2,3. Magnesium and Implications on Muscle Function. Strength and Conditioning Journal 32(1): p 48-54, February 2010. https://journals.lww.com/nsca-scj/fulltext/2010/02000/magnesium_and_implications_on_muscle_function.7.aspx

Meydani, M., Fielding, R., Martin, K.R. (1998). Vitamin E and its effect on skeletal muscle. In: Reznick, A.Z., Packer, L., Sen, C.K., Holloszy, J.O., Jackson, M.J. (eds) Oxidative Stress in Skeletal Muscle. MCBU Molecular and Cell Biology Updates. Birkhäuser, Basel. https://doi.org/10.1007/978-3-0348-8958-2_9