A healthy horse, without problems in the joints, tendons, muscles and ligaments, moves briskly, regularly, smoothly and with body use. If you let such a horse move freely or put it on the lunge, you will see wide strides of equal size, a beating rhythm in the movement and flexing muscles throughout the body. Even in the topline. Unfortunately, this is not always the reality and horses are sometimes stiff, short in movement, irregular or tighten their backs. The question is then: why is my horse stiff? There are many possible causes for stiffness in horses. Older horses often take longer to get going and heavy training and the accompanying acidification from the day before can also cause your horse to take a while to warm up. This kind of stiffness is relatively easy to remedy, by warming up well, giving some extra supplements or adjusting your training schedule a bit. It becomes more annoying when the cause of the stiffness is not so easy to determine.

Assessing horse stiffness?

If you watch your horse closely, you will often notice when your horse moves differently from normal. But very small differences are sometimes difficult to see or feel when you see and train your horse on a daily basis. Especially when you ride only your own horse and never other horses, your horse's way of moving quickly becomes normal for you. Then stiffness or other movement restrictions can 'creep in'. Therefore, it can be useful to occasionally ask someone else - your instructor, a stable mate or the vet - to assess your horse's movements. Especially if you have doubts or a 'not-fluffy' feeling.

Check your horse

When brushing your horse, it is a good idea to always run your hand over the major muscle groups of neck, shoulders, back, loins and buttocks. Push the muscles in a little, they should be smooth to push in and spring back easily. A horse with high muscle tension, where the muscles feel hard, will also be stiffer in training. If you always check how the muscles feel, you will also notice small changes faster. Warm spots on the body are also signals of possible problems.

Hard muscles?

Does your horse have hard muscles? There can be several reasons for this. The most common cause is a magnesium deficiency. This occurs because there is often too little magnesium in roughage in the Netherlands and Belgium. Magnesium is extremely important for muscles. The mineral is directly involved in the release and relaxation of muscle cells after they have been tensed (for example, to trot away or jump a hurdle). After all, muscles must not only be able to tighten but also to relax. Otherwise, they remain permanently in a kind of convulsive 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 an easily absorbed, liquid form. By the way, this mineral is not only good for muscle cells, but also important for the nervous system, energy supply and immune system!

Muscle health

Besides magnesium, vitamin E is also important for muscle health. Its action on the large skeletal muscles in particular has been much studied. Training work causes microscopic damage to muscle fibres, releasing 'oxidants'. Vitamin E in muscle tissue ensures that this so-called 'oxidative stress' is repaired (this is called the antioxidant effect). The muscle fibre recovers and is even stronger than before the training work that caused the minor damage. This is how you get training effect. For this process to work properly, there must of course be enough vitamin E in the body. The more exercise and muscle work, the higher the requirement. Note: with vitamin E, it is very important to take the right form! Many cheap supplements contain less absorbable forms of this vitamin and in horses it is very precise. It is best to feed a liquid supplement that contains the substance RRR-α-tocopherol.

Acidification, Monday sickness and muscle tremor

Great efforts can cause acidification in the muscles. Therefore, make sure you take enough breaks during training to get rid of waste products and always let your horse dismount and cool down after a competition. After a heavy training day or competition, it is a good idea to add a day of very light exercise to your training schedule. This will allow your horse to 'actively recover'. As mentioned above, supplementing magnesium and vitamin E is important. But other salts, or electrolytes, may also need to be supplemented. Especially if your horse has been sweating a lot. With Monday sickness (a form of muscle weakness), something else is going on. This is a form of stiffness caused by an incorrect feeding policy. The name refers to the practice of the past, when farmers would leave their horses stabled on Sundays and still feed them the same amount of pellets as on other days. The horses then ingested a lot of sugars, which they did not use up through hard work, as they did during the week. On Monday, the animals were then extremely stiff. Concentrates with fast carbohydrates and starch are usually not necessary for horses that do little or only light work. However, always make sure they get enough and good roughage, vitamins and minerals. A muscle-tired horse can be recognised by tight and hard muscles, stiffness and often dark urine, among other things. In severe cases, call your vet!

Stiffness due to stress

Stress and tension can also cause stiffness in your horse. This is partly because a horse tightens its muscles and shows escape behaviour when stressed. But it is also because when stressed, more magnesium is consumed by the body. This naturally leaves less for the muscles. During stressful periods such as a move, heavy training, a new herd or training and saddling, it may therefore be wise to temporarily give your horse more magnesium. Keep an eye on muscle tension and adjust your feed and training to what your horse shows.

Stiffness through compensation

Several scientific studies in recent years have shown that, unfortunately, we horse owners are not always good at recognising mild lameness in our horses. Even vets do not always agree on lamenesses. Therefore, more and more technological ways are being developed to measure lamenesses, including with motion sensors and special software. However, such methods are not widely used in practice for the time being. Moreover, it is questionable how bad a small asymmetry in a horse's movement actually is. Researchers are not quite sure about that either. Anyway, it is wise to remember that most movement problems still come from the legs. For example, from inflammation or other problems in the joints such as hooves, balls or knees, as well as tendonitis. A slight lameness in one or more legs will often cause your horse to compensate, so you see very little of it. Just think about how you yourself react when you have a sore knee or ankle. Then you start walking differently. And then you may end up suffering from your back muscles. Your back muscles are then actually not the problem, but a symptom. This is also how it works with horses. Many lamenesses are in legs but are not recognised. The horse starts compensating, which sometimes makes it seem as if the problem comes from another part of the body. Because muscles often control the compensation, stiffness can be a result.

Stiffness stays or comes back?

Have you already tried all kinds of things to solve your horse's stiffness, but with no lasting results? Then there may be more to it than just a muscle problem. When stiffness keeps coming back, while your feed policy, training schedule and supplements are in order, it is therefore good to look further. Together with your vet. Compensating for problems in the legs is one option. X-rays and ultrasound can be conclusive about joint disease or tendonitis. But strange lameness and hard and stiff muscles can also be a sign of, for example, the diseases 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