And Why One Can Become the Source of Your Problems
The purpose of this article is to help you reconsider the nature of a horse’s problematic behavior as a reflection of reflexive processes within the body, rather than a conscious choice.
We can consider two modes a horse uses to stabilize their body. One is intended for protection/survival, the other is for functional movement. We can think of these two strategies as the Extensor Stabilization neuromuscular system, and a Deep Stabilizer neuromuscular system. Each of these systems involves different dominant neural influences within the brain.
Both systems are always present. The difference is which system is dominant.
When the Extensor Stabilization system is dominant, stabilization of the body is primarily driven by subcortical and brainstem survival circuits. Pressure and sensory input are likely perceived as a threat to the animal, and the horse will react accordingly.
Treating these reactions as conscious choices is ineffective.
The horse braces for survival, tightening up the large superficial muscles to stabilize the body. This is why you lose suppleness.
When a horse is able to stabilize their body in motion using their Deep Stabilizer system, the motor cortex and cerebellum become more influential. This type of movement is functional and responsive to pressure rather than reactive.
The horse supports themselves from the deeper muscles within their body through coordination rather than bracing, allowing the large superficial muscles to behave elastically. The horse is therefore able to mobilize every part of their body to pressure from a place of secure balance.
By guiding a horse into using the Deep Stabilizer system of movement as their predominant system of movement, reactive behavior diminishes without directly confronting the behavior.
This becomes the horse’s preferred state for movement, as the body can maintain balance without triggering protective bracing.
The following charts are to illustrate the general idea of the difference in what’s going on in the body and how it affects behavior and physical functioning.
EXTENSOR STABILIZATION SYSTEM
Organizes the body for Fight or Flight
When the horse perceives instability, threat, or pain, balance of the body becomes dominated by automatic reflex and survival networks.
Neurological Control
| Level | Structures | Function |
|---|---|---|
| Brainstem | Medulla & Pons | Biases global extensor tone |
| Vestibular System | Inner ear & brainstem nuclei | Contributes to co-contraction of neck, back, and limb extensors to hold equilibrium through bracing. |
| Spinal Reflex Arcs | Local interneurons | Trigger rapid defensive contraction |
Muscular Control
The superficial muscles brace around the skeleton, preventing motion between segments, preparing the horse for survival.
| Functional Group | Muscles | Effect |
|---|---|---|
| Dorsal Topline Chain | Longissimus dorsi, Iliocostalis, Spinalis, Semispinalis capitis, Splenius | Limits spinal mobility. |
| Cervical/Head Stabilizers | Brachiocephalicus, Omotransversarius, Sternocephalicus, Rhomboideus, Trapezius | Pulls neck downward/forward; restricts base-of-neck lift. |
| Thoracic Sling (in brace mode) | Superficial & Deep Pectorals, Latissimus dorsi | Contributes to downward loading of the thorax |
| Hindquarter Extensors | Gluteus medius, Superficial gluteal, Biceps femoris, Semitendinosus, Semimembranosus, Quadriceps femoris | Drives hind extension; limits mobility of pelvis. |
| Ventral Chain | Rectus abdominis, External oblique | Contribute to trunk rigidity, limiting ribcage expansion and breath adaptability. |
| Tail & Sacral Fixators | Sacrococcygeus dorsalis/ventralis, Intertransversarii caudae | Limits mobility of sacrum and tail |
DEEP STABILIZER SYSTEM
Functional Movement
This is a system of stability for functional movement and responsiveness to pressure rather than reactivity.
Neurological Control
| Level | Structures | Function |
|---|---|---|
| Motor Cortex | Frontal lobe | Initiates voluntary, coordinated movement; supports fine motor control. |
| Cerebellum | Hindbrain | Regulates timing, rhythm, balance; smooths transitions between flexion and extension. |
| Propriospinal Interneurons | Within spinal cord | Integrate limb and core coordination; contribute to diagonal stability |
| Sensory Feedback Loop | Muscle spindles, Golgi tendon organs, joint mechanoreceptors | Provide continuous feedback; proprioception |
Muscular Control
Deep stabilizers maintain joint alignment for mobility. Superficial muscles return to rhythmic, elastic function.
| Functional Group | Muscles | Effect |
|---|---|---|
| Deep Axial | Multifidus, Rotatores, Interspinales, Intertransversarii | Segmental spinal control; maintain alignment while allowing mobility. |
| Iliopsoas Complex | Psoas major, Psoas minor, Iliacus | Pelvic flexion and rotation |
| Abdominal Pressure System | Transversus abdominis, Internal oblique, Diaphragm | Regulate internal pressure |
| Pelvic Floor Group | Coccygeus, Levator ani (iliococcygeus + pubococcygeus), Perineal fascia | Synchronize with diaphragm for pelvic stability. |
| Thoracic Sling | Serratus ventralis thoracis & cervicis, Subclavius, Deep pectoral | Lift thorax between scapulae; diagonal coordination |
| Cervical | Longus colli, Longus capitis, Rectus capitis ventralis, Scalenus ventralis | Align cervical vertebrae; supports alignment and functional elevation of the base of the neck. |
| Hip Rotators / Deep Gluteals | Gluteus profundus, Obturator internus & externus, Gemelli, Quadratus femoris | Coordinate pelvic alternation |