[Biomechanics, Tensegrity & Meridian Concepts 11] How Core Stability Restores Tension Balance Across the Vertebrae

Introduction

The spine is constantly exposed to forces. Gravity compresses the body, muscles generate stabilizing forces, the ground produces reaction forces, and movements of the arms, pelvis, and legs transmit additional loads through the trunk.

A healthy spine does not eliminate these forces. Instead, it continuously distributes and manages them.

This is where core stability becomes important.

The term core stability is often used to describe the ability of the trunk and surrounding musculature to control the position and movement of the spine and pelvis. It involves much more than abdominal strength. The diaphragm, abdominal wall, multifidus, erector spinae, pelvic floor, quadratus lumborum, and other muscles contribute to trunk control in different ways.

In scoliosis, asymmetric spinal geometry can change how these muscles work. Differences in vertebral position, spinal rotation, pelvic alignment, and muscle morphology may alter the distribution of mechanical loads across the trunk. Research has identified associations between paraspinal muscle characteristics and spinal curvature, although the direction of causation remains uncertain. [1]

Core stabilization exercise has been studied as one component of conservative scoliosis management. A 2025 systematic review and meta-analysis of 10 studies involving 449 participants found that core stabilization exercise was associated with improvements in Cobb angle, trunk rotation, apical vertebral rotation, and quality of life compared with no exercise, although the evidence was heterogeneous and the effects were smaller than those reported for some three-dimensional exercise programs. [2]

The important question, therefore, is not simply whether stronger abdominal muscles straighten the spine.

A more useful question is:

Can better neuromuscular control help the body distribute spinal forces more efficiently and maintain a more balanced alignment?

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1. What Is Core Stability?

Core stability is the ability of the trunk to control the position and movement of the spine and pelvis during static and dynamic activities.

It involves coordination among multiple systems rather than the contraction of one particular muscle.

Important contributors include:

• Diaphragm
• Transversus abdominis
• Internal and external obliques
• Rectus abdominis
• Multifidus
• Erector spinae
• Quadratus lumborum
• Pelvic floor muscles
• Gluteal muscles
• Hip musculature

These muscles work together with the nervous system to regulate trunk stiffness and movement.

The objective is not to make the spine completely rigid.

Instead, the trunk must be stable enough to control movement while remaining mobile enough to move efficiently.

This distinction is essential.

A completely rigid spine would not be functional. Walking, breathing, reaching, and rotating all require controlled spinal movement.

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2. Stability Does Not Mean Rigidity

The word “stability” can be misleading.

A stable spine is not necessarily a motionless spine.

During normal movement, the spine undergoes small changes in:

• Flexion
• Extension
• Rotation
• Lateral bending
• Compression
• Shear

The muscles continuously adjust their activation to control these movements.

Therefore, core stability can be understood as controlled adaptability.

The nervous system must determine:

How much muscle activation is necessary for this particular movement?

Too little activation may reduce control.

Too much activation may increase stiffness, fatigue, and energy expenditure.

The ideal strategy is therefore not maximal contraction but appropriate coordination.

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3. What Does “Tension Balance” Mean?

“Tension balance” is a useful biomechanical concept, but it should not be confused with a formally established clinical diagnosis.

In this context, it refers to the relationship among:

• Muscle tension
• Ligament tension
• Fascial tension
• Compression
• Shear
• Bending moments
• Torsional forces
• Ground-reaction forces

The spine constantly seeks mechanical equilibrium.

For example, when a person stands upright, gravity produces a downward force. Muscles generate opposing forces that help prevent excessive forward, backward, or sideways displacement.

If the trunk shifts, the muscular forces required to maintain equilibrium change.

This can be represented conceptually as:

External force → spinal displacement → sensory feedback → muscle response → redistribution of force

Core stability contributes to this feedback system.

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4. The Spine as a Load-Distribution System

Each vertebral segment participates in transmitting loads through the spine.

Structures involved include:

• Vertebral bodies
• Intervertebral discs
• Facet joints
• Ligaments
• Paraspinal muscles
• Abdominal muscles
• Thoracolumbar fascia
• Pelvis

The load is not carried by the vertebral bodies alone.

Muscles can change the mechanical environment of the spine by producing forces across multiple segments.

For example, activation of the trunk muscles can increase spinal stiffness and influence how external loads are transmitted through the vertebral column.

This is why core stability is better understood as load management rather than simply “abdominal strengthening.”

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5. What Changes When the Spine Becomes Asymmetric?

In scoliosis, the vertebral column becomes three-dimensionally asymmetric.

This may include:

• Coronal curvature
• Vertebral rotation
• Vertebral wedging
• Rib-cage asymmetry
• Altered sagittal alignment
• Pelvic compensation
• Trunk shift

These structural changes can alter the mechanical environment of the muscles.

A systematic review of paraspinal muscle characteristics in AIS found low- to very-low-strength evidence for differences between the concave and convex sides, including differences in muscle volume, fiber characteristics, activity, and fatty infiltration. The review also emphasized that these muscle changes may be either a cause or a consequence of the spinal curvature. [1]

This distinction is critical.

A person may develop altered muscle activation because the spine is asymmetric, rather than the muscle imbalance being the original cause of the scoliosis.

The relationship can therefore be bidirectional.

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6. How Muscle Forces Influence Spinal Loading

Muscles generate forces that can influence spinal compression and stability.

When the trunk muscles contract, they create forces around the spinal column.

These forces can:

• Increase segmental stability
• Control movement
• Resist external perturbations
• Modify spinal loading
• Help maintain upright posture

However, stronger contraction does not automatically mean better alignment.

Excessive or poorly coordinated contraction can increase compression without producing useful corrective movement.

Therefore, the important variable is not simply how much force the muscles generate.

It is:

where, when, and in which direction the force is generated.

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7. Why Direction Matters

A force has both magnitude and direction.

Suppose a muscle produces a force that helps resist lateral displacement. That may improve frontal-plane stability.

Another muscle activation pattern may primarily resist rotation.

Another may control flexion or extension.

The trunk therefore requires coordinated forces across multiple planes.

This is particularly important in scoliosis because scoliosis is three-dimensional.

A rehabilitation strategy that addresses only lateral bending may not fully address:

• Axial rotation
• Sagittal alignment
• Rib-cage position
• Pelvic orientation

This is one reason why scoliosis-specific exercise approaches frequently emphasize three-dimensional correction rather than isolated strengthening.

A 2024 systematic review and meta-analysis found that physiotherapeutic scoliosis-specific exercises produced positive effects on Cobb angle, angle of trunk rotation, and thoracic kyphosis compared with other nonsurgical approaches, although the evidence quality varied and further research was recommended. [3]

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8. Core Stability and the Neutral Spine

A commonly used concept in exercise rehabilitation is the neutral spine.

Neutral does not mean perfectly straight.

The human spine normally contains:

• Cervical lordosis
• Thoracic kyphosis
• Lumbar lordosis
• Sacral curvature

A functional neutral position is therefore a region in which the spine can tolerate movement and loading efficiently.

In scoliosis, however, the patient's neutral position may be asymmetric.

One shoulder may sit higher.

The pelvis may shift.

The rib cage may rotate.

The trunk may translate relative to the pelvis.

Therefore, core training should not simply force every patient into the same generic “neutral” posture.

The appropriate target should be individualized.

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9. Deep and Superficial Muscles Work Together

Core stability is sometimes incorrectly reduced to the deep abdominal muscles.

In reality, trunk control involves coordination between deep and superficial muscles.

Deep stabilizing muscles

These include:

• Multifidus
• Transversus abdominis
• Diaphragm
• Pelvic floor

They contribute to segmental and pressure-related control.

Larger movement muscles

These include:

• Rectus abdominis
• External oblique
• Internal oblique
• Erector spinae
• Quadratus lumborum
• Gluteal muscles

They contribute to larger trunk and pelvic movements.

The two groups are not independent.

During functional movement, they operate as a coordinated system.

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10. The Diaphragm Is Part of the Core

Breathing and trunk stability are closely connected.

The diaphragm is the primary muscle of respiration, but its position and activity also influence abdominal pressure and trunk mechanics.

During inhalation, the diaphragm descends.

During exhalation, it rises.

The abdominal muscles and pelvic floor interact with these changes in pressure.

For this reason, some rehabilitation approaches integrate:

• Breathing
• Trunk elongation
• Rib-cage correction
• Abdominal control
• Postural stabilization

This is especially relevant to scoliosis because thoracic deformity can alter rib-cage mechanics.

However, breathing exercises should not be described as directly correcting the underlying vertebral deformity unless supported by appropriate evidence.

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11. Core Stability and the Pelvis

The pelvis forms the mechanical bridge between the spine and lower extremities.

Its position influences the orientation of the lumbar spine.

Pelvic position can change with:

• Hip position
• Leg-length discrepancy
• Muscle imbalance
• Foot mechanics
• Standing strategy
• Spinal curvature

For example, pelvic obliquity may produce compensatory trunk movement.

Core muscles must then work to maintain the head and trunk over the base of support.

This creates another mechanical chain:

Feet → legs → pelvis → lumbar spine → thorax → head

Core stability therefore cannot be understood independently of the pelvis and lower extremities.

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12. Core Stability and the Tensegrity Concept

The idea of biotensegrity provides one conceptual model for understanding how tension and compression interact throughout the body.

In a tensegrity-inspired model, stability emerges from the interaction of:

• Tension elements
• Compression elements
• Structural geometry
• Distributed forces

The human body is considerably more complex than a simple engineered tensegrity structure, and biotensegrity should therefore be regarded as a conceptual biomechanical model rather than an established explanation for idiopathic scoliosis.

Nevertheless, the concept is useful for visualizing why a change in one region may alter mechanical demands elsewhere.

For example:

Pelvic position → trunk muscle activity → spinal loading → shoulder and head position

Core stability can therefore be viewed as part of a distributed system rather than an isolated abdominal function.

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13. What Happens When Core Control Is Poor?

Poor core control does not necessarily mean that the abdominal muscles are weak.

A person may have strong muscles but poor coordination.

Possible characteristics include:

• Delayed muscle activation
• Excessive co-contraction
• Poor pelvic control
• Reduced trunk endurance
• Excessive trunk movement
• Difficulty maintaining alignment during movement
• Compensatory shoulder or pelvic motion

For example, an athlete may produce substantial abdominal force during a static exercise but still lose trunk control during single-leg movement.

Functional stability is therefore different from isolated muscle strength.

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14. Core Stability and Neuromuscular Feedback

Core stability depends heavily on sensory information.

The nervous system receives information from:

• Muscles
• Tendons
• Joints
• Skin
• Vestibular system
• Vision

It then adjusts muscle activation.

This creates a continuous loop:

Position → sensory information → nervous-system processing → muscle activation → movement → new position

This is particularly relevant in scoliosis because spinal asymmetry may alter the sensory and mechanical information available to the nervous system.

Research has identified differences in proprioception, postural stability, and muscle activation in some patients with AIS. These findings support the importance of neuromuscular control but do not prove that impaired feedback causes scoliosis. [4]