How do we use our muscles when playing an instrument?

Although this article has a somewhat “technical” focus, I want to explain it as clearly and simply as possible. This is not a medical text, nor is it intended to provide a deep scientific explanation. It is an introduction specifically designed for musicians, to start understanding the basics of muscular function—a fundamental topic for grasping what really happens in our bodies when we play an instrument.

The three main ways we use our muscles:

1. Changing their length

A clear example is when we bend the elbow. This joint is connected on the inside by muscle, attached at one end to the forearm bone and at the other end to the upper arm bone.

This allows the muscle fibers to contract, shortening and bringing the forearm closer to the arm, reducing the angle of the elbow joint (flexion). Similarly, when we extend the elbow, the angle increases, but in this case, the active muscles are positioned on the outside of the joint.

Flexion and extension movements are not due to different types of muscles—they depend on where they are attached and what kind of movement they can produce when contracting.

2. Changing the level of tension in a muscle

This occurs when we maintain a joint angle against resistance, such as weight or opposing pressure. For example, when holding something with a bent elbow (like a flute, clarinet, etc.).

We should not assume that contraction always means shortening, or that relaxation always means lengthening. It depends on circumstances, such as the influence of gravity or opposing muscles. Contraction might shorten a muscle, moving a bone, or simply tension it enough to maintain its length against resistance (from another muscle or an external force, including gravity).

3. Without changing length or tension

We also use muscles to prevent changes in length or tension. This happens when we keep them in their current state, either continuing their work or simply preventing interference where they are not needed.

This function becomes clearer when we remember that muscles do not work in isolation. They work in groups—sometimes very large, spanning from the head to the fingers and toes—and their relationships are complex.

When performing a movement, we use:

• Prime movers: muscles responsible for the action.

• Antagonists: muscles that oppose the prime movers and must relax, but not too quickly, or the movement will be abrupt.

• Stabilizers: muscles that stabilize the part of the body over which the moving part works (like the frame of a door).

• Postural muscles: muscles that maintain body balance during movement.

• Structural support muscles: muscles that preserve the shape of the body and the integrity of the structure where movement occurs.

• “Passive” muscles: muscles we don’t want to engage; we inhibit them (consciously or unconsciously) to prevent interference. This negative use of muscles is very important.

Muscle functions

Regarding movement, we can broadly speak of three muscle functions without overcomplicating things:

• Strength

• Endurance

• Balance or stability

These three functions depend largely on our flexibility.

What is flexibility and what does it depend on?

Flexibility is the range of motion of each of our joints. It is important to understand that everyone has a genetic predisposition to a certain degree of “stiffness” or “flexibility.” In addition, bone structure varies from person to person, which also sets limits on the movements we can perform.

Our bones are not identical; they differ in size, shape, and rotation, which greatly influences movement. That’s why trying to imitate movements or postures without considering your own structure can lead to injuries.

This is why I do not believe in a single “correct posture” for playing a given musical instrument. I always aim for each person to find a constructive relationship between their joints by observing their own movement, rather than trying to reproduce a supposedly “correct” image.

How can we become more flexible?

It is often thought that repeating stretches every day so that “our muscles get used to it” is the most efficient way to gain flexibility. However, recent studies have challenged many mechanical theories. Today we know that flexibility depends largely on our nervous system.

Our flexibility is related to the point at which we believe we can continue moving a joint. It develops much more quickly when we trust our bodies than when we mechanically repeat an exercise.

Of course, stretching exercises are essential for developing greater flexibility, but they are much more effective and healthy depending on how they are performed and how consciously they are directed (returning to the topic of mindful use).

Strength

Having strong muscles does not guarantee that they will activate efficiently for coordinated movement. Glenn Withers (physiotherapist for Manchester United) mentions:

“Having worked with several football teams over the past 10 years, I can say that the main problem for many elite footballers is that they have excellent strength training but almost completely lack stability. This lack of joint stability is the main source of injuries in professional sports.”

Strength allows us to perform explosive, fast, powerful, and momentary movements. The key question here is: how much strength do we really need to play our musical instrument?

For movement to be efficient, the key is developing active coordination of the body as a unit, not just training isolated muscle groups. We obviously need some strength to play, but we probably use far more than necessary.

Stability

Stability is the nervous system’s ability to respond efficiently to imbalance. It allows us to balance the skeleton, keep joints aligned, and move through the world.

When someone lacks stability, their joints are at greater risk of dislocation (as happens with some high-performance athletes). Our stability depends on the autonomic nervous system, and we have little direct control over the muscles that provide it.

Since strength is muscular activity we can consciously access, any attempt to generate stability artificially will make us use force to stay stable, generating unnecessary tension.

Stability is something we must allow, not something we must “do.”

Endurance

Strength is often confused with endurance, but they are not the same.

Endurance is controlled by different muscle fibers: postural muscles, which work all day to keep us upright against gravity. These are also largely autonomous, and we cannot control them directly.

Like stability muscles, postural muscles need to be left to work on their own. Any attempt to generate endurance (for example, when feeling fatigued) leads to unnecessary tension.

That’s why the idea of “pushing as hard as possible” can be counterproductive, especially when the body is asking for rest. Any effort can easily turn into unneeded muscle tension.

The importance of rest

Once we understand how our muscles work and their specific functions, it is essential to learn to rest actively and include breaks as a fundamental part of our daily musical practice.

If you are interested in learning more about how to use active rest constructively within your practice, I invite you to read my article on “Block practice strategies and constructive rest for musicians”.

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