[Exercise, Rehabilitation & Movement Therapy 03] The Role of Core Muscle Engagement in Supporting Spinal Alignment

Introduction

The term “core strength” is widely used in fitness, sports, and rehabilitation.

People are often told that a strong core can improve posture, protect the back, and help maintain spinal alignment. While trunk muscles clearly contribute to movement and force management, these relationships are more complex than the simple idea that a strong core equals a straight spine.

The muscles surrounding the trunk contribute to trunk control, movement, and the management of forces during everyday activities. Their activity changes continuously as the body responds to gravity, movement, breathing, external resistance, and changes in position.

For people with scoliosis, trunk control may be one relevant component of a broader rehabilitation strategy. Scoliosis is a three-dimensional spinal deformity involving lateral curvature and vertebral rotation, meaning that rehabilitation may need to consider more than general abdominal strength. [1]

Core stabilization exercise has been studied in adolescent idiopathic scoliosis (AIS), and recent research suggests that it may provide benefits for some patients. However, current evidence does not support presenting core exercise as an independent method for correcting scoliosis or as a universal treatment. [2]

The more accurate concept is:

Core muscle engagement can support controlled movement and load management, but it is only one component of spinal and postural function.

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1. What Does “Core” Actually Mean?

The core is not a single muscle.

It is better understood as a functional region involving multiple muscles that contribute to control of the trunk and lumbopelvic region.

These include, depending on the movement:

• abdominal muscles,
• internal and external obliques,
• transverse abdominis,
• multifidus,
• erector spinae,
• quadratus lumborum,
• diaphragm,
• pelvic floor muscles,
• and muscles surrounding the pelvis and hips.

The contribution of each muscle varies according to the task.

For example, the muscular demands of a plank are different from those of walking, lifting, running, or rotating the trunk.

Therefore, core function is dynamic rather than simply a state of keeping the abdomen tight.

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2. Spinal Alignment Is Not a Fixed Position

The word alignment can sometimes create the impression that the spine should remain perfectly straight and motionless.

That is not how the human body normally functions.

The spine moves during:

• walking,
• running,
• sitting,
• standing,
• lifting,
• reaching,
• rotation,
• and breathing.

Maintaining appropriate alignment therefore does not mean eliminating spinal movement.

Instead, it involves the ability to control movement while responding appropriately to changing forces and tasks.

Core muscle activity is one part of this process.

A useful way to understand core engagement is:

The core contributes to the regulation of trunk movement rather than simply preventing movement.

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3. What Is Dynamic Spinal Stability?

Spinal stability is sometimes incorrectly interpreted as rigidity.

In normal movement, the spine needs both:

sufficient control to transmit forces

and

sufficient mobility to allow movement.

During a squat, for example, the trunk needs to remain controlled while the hips and knees move.

During walking, the trunk needs to accommodate movements generated by the lower limbs.

During lifting, the trunk and hip muscles work together to manage forces transferred through the body.

This is often described as dynamic stability.

The objective is not to eliminate all spinal movement.

It is to develop appropriate control of movement for the task being performed.

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4. How Core Muscles Contribute to Load Management

Daily activities expose the body to many types of forces.

These can arise from:

• body weight,
• gravity,
• muscle contraction,
• external objects,
• ground reaction forces,
• acceleration,
• and changes in body position.

Trunk muscles contribute to how the body responds to these forces.

For example, when lifting an object, the muscles of the trunk and hips help control the relationship between the spine, pelvis, and lower limbs.

When reaching overhead, the trunk adjusts to changes in the body's center of mass.

When walking, trunk activity is coordinated with movement of the pelvis and lower limbs.

Therefore, core engagement is better understood as part of a broader force-management and movement-control system.

It does not mean that the muscles simply hold individual vertebrae in a fixed position.

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5. Why Trunk Control May Be Relevant to Scoliosis

A person with scoliosis may have differences in:

• spinal alignment,
• vertebral rotation,
• trunk position,
• pelvic position,
• muscle activation,
• thoracic shape,
• balance,
• and habitual movement patterns.

These characteristics can influence how the trunk behaves during movement.

Trunk-control exercises may therefore be useful for developing the ability to perform movements with greater control.

However, this should not be confused with structural correction.

There is an important distinction between:

Core training → developing strength or trunk-control capacity

and

Structural correction → changing the underlying spinal deformity.

Improving one does not automatically produce the other.

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6. Core Engagement Is Not Simply “Tightening Your Abs”

A common exercise instruction is:

“Tighten your core.”

This can be a useful teaching cue, but maximal abdominal contraction is not necessarily the goal of every movement.

Excessive or prolonged bracing may interfere with:

• normal breathing,
• movement,
• relaxation,
• or task-specific coordination.

The appropriate level of trunk muscle activity depends on what the person is doing.

A person lifting a heavy object may require a different strategy from someone walking or performing a gentle mobility exercise.

Effective core training therefore involves both:

activation

and

controlled movement.

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7. The Diaphragm and Trunk Function

The diaphragm is primarily a respiratory muscle, but breathing is also closely related to trunk function.

During inhalation, the diaphragm changes its position and interacts mechanically with the abdominal contents and surrounding trunk structures.

At the same time, the body must continue to control posture and movement.

This creates an ongoing interaction between:

breathing + trunk control + posture + movement.

In people with thoracic scoliosis, the relationship between the spine and rib cage may have additional relevance because thoracic deformity can affect thoracic geometry and respiratory mechanics.

Some scoliosis-specific exercise approaches therefore incorporate breathing with individualized postural correction. [3,4]

This does not mean that breathing exercises alone are established as a method for correcting structural scoliosis.

Rather, breathing can be incorporated into a broader movement strategy.

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8. Core Muscles Function as a Coordinated System

It is tempting to identify one muscle as the “most important” core muscle.

In reality, trunk control involves coordinated activity among multiple structures.

Abdominal Muscles

Contribute to trunk control and force transmission.

Spinal Muscles

Contribute to spinal movement and control.

Diaphragm

Contributes primarily to respiration and also interacts with trunk function.

Pelvic Floor

Participates in pressure regulation and lumbopelvic function.

Hip Muscles

Contribute to force transfer between the lower limbs and pelvis.

The exact contribution of each structure varies according to the task.

Therefore, coordination is at least as important as isolated muscle strength when considering functional trunk control.

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9. The Relationship Between Core and Pelvic Control

The pelvis forms an important connection between the spine and lower limbs.

During walking, running, squatting, or lifting, forces are transferred through the kinetic chain:

feet → legs → pelvis → spine → trunk

and in the opposite direction:

trunk → spine → pelvis → legs → ground.

Control of the pelvis can therefore influence how movement is transferred through the trunk.

For people with scoliosis, pelvic position may also interact with their existing spinal alignment.

This does not mean that pelvic position is established as the cause of idiopathic scoliosis.

Instead, it means that pelvic and trunk control may be relevant to how an individual moves with an existing spinal deformity.

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10. Stability Does Not Mean a Rigid Spine

One of the most important concepts in movement rehabilitation is that stability does not necessarily require rigidity.

A completely rigid spine would interfere with many normal activities.

The body needs controlled mobility.

The trunk must be able to participate in:

• flexion,
• extension,
• rotation,
• lateral flexion,
• and translation

when the task requires it.

Core muscles contribute to controlling these movements.

Therefore, the objective of core training is generally not to make the spine permanently stiff.

It is to improve the ability to control movement under different conditions.

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11. Core Exercise Is Not the Same as Scoliosis-Specific Exercise

This distinction is especially important for patients with scoliosis.

General core exercises may include:

• planks,
• side planks,
• bridges,
• bird dogs,
• dead bugs,
• abdominal strengthening,
• and resistance exercises.

These exercises can be used to develop general trunk strength or control.

Physiotherapeutic scoliosis-specific exercises (PSSE), however, have additional principles.

Depending on the specific method, these may include:

• individualized three-dimensional self-correction,
• stabilization of the corrected posture,
• elongation,
• breathing strategies,
• and integration into daily activities. [3,4]

Therefore:

Core exercise and scoliosis-specific exercise are not interchangeable terms.

Core training may be incorporated into a broader rehabilitation program, but it does not replace individualized scoliosis assessment or scoliosis-specific treatment when such treatment is indicated.

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12. What Does the Research Say About Core Stabilization?

Research specifically examining core stabilization exercise in AIS has increased in recent years.

A 2025 systematic review and meta-analysis included 10 randomized controlled trials involving 449 participants with mild to moderate AIS. The authors reported that core stabilization exercise was associated with improvements in Cobb angle, angle of trunk rotation, apical vertebral rotation, and SRS-22 quality-of-life scores compared with a no-treatment or blank-control condition. However, core stabilization showed weaker effects than three-dimensional exercise for several outcomes, and the authors emphasized heterogeneity, small sample sizes, multiple comparisons, and the need for longer-term research. [2]