This article was originally published here.

The skeletal striated muscles are the most visible muscles and we have more than 600 of them. They give the body its shape and their total mass represents more than half the bodyweight of an adult. These are the muscles responsible for our voluntary movements because they contract when we ask them to. They also allow us to control our posture and hold and move our joints. Detailed explanations...
1. What Makes Up A Muscle

A muscle is made up of a multitude of cells called muscle fibres. They are grouped into bundles called muscle fascicles that are nourished by blood vessels supplying the energy needed by the fibres.

Muscle fibres can range from just a few millimetres to more than 10 centimetres long. They contract with the help of very fine filaments called myofilaments which are organised in myofibrils. The filaments slide over one another during the exercise as they tighten. This allows the muscle to contract and relax and so on.

Bear in mind that the myofilaments are made of the following 2 types of molecules:

• Actin (very fine filament)

• Myosin (thicker filament)

It is precisely these two kinds of filaments that are at the origin of the contraction.
2. How Does Muscle Contraction Work

The muscles are in fact simply a tool that implements the contraction. Indeed, it is the brain that gives the order and chooses to contract the muscle.

When we decide to perform this action, we order the brain to send a signal to the muscle. The motor cortex is the area of the brain that receives this order. The latter receives the information from several regions of the brain which give the direction of the movement, its speed, etc.

The cortex analyses this information and translates it into nerve impulses that are sent to an initial neuron. The electrical signal generated by the nerve impulse flows through the length of this neuron.

In order to reach the muscle, the nerve impulse must go through several stages. Then in the upper part of the spinal cord, the relay is passed to a second neuron called the motor neuron that reaches the muscle so that the nerve impulse can stimulate it.

The end of this motor neuron is divided into several nerve endings and each of these endings comes into contact with the muscle fibre.

The connection of the motor neuron with the fibres is called the motor unit.

Moreover, the meeting point between the motor neuron and the fibres is called the neuromuscular junction. This is where the electrical signal triggers the release of chemical molecules, i.e. the so-called neurotransmitters.

A sequence of electrical phenomena then occurs which allows the released molecules to move to the filaments so that they contract. This occurs at the same time in the large number of muscle fibres distributed throughout the muscle.

After all that, the muscle works!

3. Muscle Pain

When used to excess or not enough, a muscle can hurt. Different circumstances, which are more or less common, can cause muscle pain. The most commonly occurring are the following three phenomena:

Stiffness

This is caused by micro-tears in the muscle fibres for which the body triggers a small inflammatory reaction to repair them. They occur when the muscle is not used to an exercise that it is being asked to perform. They are usually painful for 12 to 48 hours after exercise and last 5 to 7 days depending on their intensity.

Muscle Contractures

This is a painful and lasting contracture of a muscle caused by its excessive use. There are different kinds of contractures:

• Primitive muscle contracture: when the muscle is used intensively and for a prolonged period without recovery

• Muscle contracture with lesion: the muscle is physically injured in the case of a tear, elongation or strain

• Defensive muscle contracture: defence mechanism of an injured joint.

Muscle contractures affect especially the calves, the thighs, the buttocks, the muscles of the neck and the back. They are caused by the muscle fibres contracting.

Cramp

These are spontaneous and sustained muscle contractions. The muscle contracts involuntarily and does not relax for a short time, ranging from a few seconds to a quarter of an hour. They often occur during exercise or at night (so-called night cramps).
4. Muscle Maintenance

To avoid this type of pain, you must take care of your muscles before, during and after exercise.

An essential part of this is hydration as well as warming up and stretching properly at the end of each sports training session.

It is also important to avoid excessive training and listen to your body when you feel pain.

Finally, it is good to know that warmth helps to relieve muscle pain. Nothing beats a good hot bath after training!