1. Opening Summary Paragraph
In clinical neurophysiology and our Physiotherapy & Sports Medicine Glossary, Henneman’s Size Principle defines the foundational biomechanical law dictating that motor units are recruited in a precise sequence from smallest to largest based on the magnitude of physical demand. When sedentary habits or chronic pain disrupt this neural ladder, individuals experience a "neurological stutter" where the deep, slow-twitch core stabilizers fail to fire, forcing high-threshold global muscles to compensate and sparking acute lumbar shear and muscle spasms. Physiotherapy in Toronto at Queen West Rehab Mechanics assists active adults and lifters in managing this neuromuscular timing failure by isolating the specific recruitment gaps during a comprehensive biomechanical movement assessment, retraining anticipatory core control, and progressively loading the spine via Heavy Slow Resistance (HSR) training to restore an automated, injury-resistant muscular brace.
2. The Patient’s Story / Toronto Context
Across downtown Toronto’s dynamic professional hubs—from the creative agencies in Liberty Village and software lofts in King West to remote workers navigating tight deadlines near Queen West—the modern workday demands eight to twelve hours of static, seated immobility, leading directly to workplace postural dysfunction.
Consider a 32-year-old digital project manager and recreational powerlifter living near Trinity Bellwoods. Throughout the week, they sit slouched at their desk, leaving their deep spinal stabilizers completely unweighted. When the weekend arrives, they transition rapidly to heavy deadlifts in their local Liberty Village gym or high-intensity sprints along the Martin Goodman Trail.
Suddenly, they encounter The Neurological Lifting Catch.
When attempting to pull a heavy barbell off the floor or pick up a heavy box of groceries, their lower back seizes with a sharp, breathtaking "pop" indicative of facet joint arthropathy. They are physically strong enough to lift the weight, but their deep core (transversus abdominis) failed to activate in time to protect the lumbar spine.
Following standard gym advice, they fall into The Conscious Clenching Trap. They try to forcefully squeeze their abdominal muscles and hold their breath to protect their back, making their movements rigid and exhausting. Inside our private clinical suites at Rehab Mechanics inside the Prime Medical Centre at 68 Abell Street in Queen West, we show athletes that core stability must be automated. By utilizing clinical biofeedback and precision motor control drills, we recalibrate Henneman's Size Principle, ensuring the small stabilizing muscles fire instantly before the large moving muscles take over, protecting the spine across Toronto.
3. Structural / Biomechanical Analysis
To understand why a failure in motor unit recruitment causes severe lower back catching—and how physical therapy systematically restores this pathway—we must examine The Motor Unit Recruitment Ladder and Feedforward Stabilization.
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| HENNEMAN'S SIZE PRINCIPLE: MOTOR UNIT RECRUITMENT VS. KINETIC CHAIN SHEAR |
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| [A] THE RECRUITMENT FAILURE TRAP [B] THE REHAB MECHANICS RECRUITMENT MATRIX |
| (Sedentary Inhibition + High-Velocity Demand) (Biofeedback Training + HSR Loading) |
| |
| Rapid, Heavy Lifting After Prolonged Sitting Targeted Deep Core Motor Re-Education |
| + Small Motor Units (Type I) Remain Dormant + Progressive Motor Unit Activation |
| | | |
| v v |
| 1. THE HIGH-THRESHOLD JUMP: 1. AUTOMATED FEEDFORWARD SEQUENCE: |
| • Nervous System Bypasses Small Stabilizers • Small, Slow-Twitch Units Fire First |
| • Fires Large (Type II) Prime Movers Instantly • Transversus Abdominis Locks Lumbar Spine|
| • Unbuffered Rotational Shear Strikes Spine • Anticipatory Brace Prevents Facet Shear |
| | | |
| v v |
| 2. COMPENSATORY MUSCLE SPASM: 2. HIGH-LOAD KINETIC TRANSFER: |
| • Sinuvertebral Nerves Detect Joint Shear • Large (Type II) Motor Units Engage Next |
| • Spinal Cord Triggers Protective Back Spasm • Smooth, Powerful Lifting Execution |
| • Pain Shuts Down Further Motor Drive • Maximum Force Generated Without Injury |
| | | |
| +--------------------+--------------------+ +-----------------+--------------------+ |
| | THE PERPETUAL LIFTING STALEMATE | | THE BULLETPROOF NEURO-CHASSIS | |
| | • Frequent sharp lower back catches | | • Subconscious, automatic core brace | |
| | • Inability to progress gym weights | | • Flawless heavy lifting mechanics | |
| | • Reliance on thick weightlifting belts| | • Zero mid-lift spinal buckling | |
| | • Chronic fear of bending and lifting | | • Permanent athletic longevity | |
| +-----------------------------------------+ +--------------------------------------+ |
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The Alpha Motor Neuron Pool
According to Henneman’s Size Principle, the central nervous system minimizes fatigue by recruiting motor units in a strict, sequential order. Small, fatigue-resistant Type I (slow-twitch) motor units have low electrical thresholds and are recruited first for postural tasks. As load increases, larger Type II (fast-twitch) motor units are recruited to generate explosive power and coordination.
The High-Threshold Recruitment Gap
When a desk worker spends hours sitting, their small postural motor units become inhibited, often presenting as gluteal amnesia. If they suddenly jump into a heavy lift, the brain struggles to fire the dormant small units and skips directly to the massive, high-threshold units. This forces the large global movers (like the rectus abdominis or spinal erectors) to act as stabilizers, a job they are ill-equipped for. The result is uncoordinated, jerky movement that exposes the lumbar intervertebral discs to catastrophic shear forces.
The Feedforward Core Brace
Physical therapy restores this sequence by retraining the anticipatory feedforward mechanism (Anticipatory Core Control). By using low-load, high-attention exercises like The DeadBug Blueprint, we force the nervous system to re-engage the small motor units supplying the transversus abdominis and multifidus, ensuring they fire $30\text{ to }110\text{ milliseconds}$ before the arms and legs move, locking the spine into a safe, pressurized cylinder.
4. Clinical Red Flags
While neuromuscular timing issues respond exceptionally well to physical therapy, clinicians must screen for neurological and structural red flags that demand immediate medical escalation:
Progressive Motor Foot Drop: Sudden, unprovoked inability to lift the foot or toes (dorsiflexion) during walking, signaling active L4 or L5 motor axon compromise (Peroneal Nerve Palsy & Gait Retraining).
Cauda Equina Syndrome Symptoms: New-onset urinary retention, bowel incontinence, or saddle anesthesia across the groin, representing an absolute surgical emergency requiring immediate 911 activation.
Radicular Electric Shocks: Severe, sharp electric-shock pain shooting past the knee into the foot during basic movement, indicating acute disc herniation or chemical nerve root impingement (Mapping Dermatomes and Sciatica Paths).
Unremitting Night Pain: Deep spinal bone pain that wakes the patient from sleep and remains unchanged by positional shifts, demanding oncological screening.
5. Primary Source Proof (PubMed / NIH)
Review the Clinical Evidence on PubMed: The Size Principle and Motor Unit Recruitment: Mechanisms of Neuromuscular Control in the Lumbar Spine (National Institutes of Health / Journal of Neurophysiology)
Review the Clinical Evidence on PubMed: Feedforward Activation of the Transversus Abdominis and Multifidus: Implications for Lower Back Pain Rehabilitation (National Institutes of Health / Spine)
Review the Clinical Evidence on PubMed: Electromyographic Analysis of Motor Unit Synchronization During Heavy Resistance Training (National Institutes of Health / Journal of Applied Physiology)
Review the Clinical Evidence on PubMed: Corticospinal Excitability and the Modulation of the Motor Pool in Chronic Musculoskeletal Pain (National Institutes of Health / Journal of Orthopaedic & Sports Physical Therapy)
6. The Rehab Mechanics Corrective Protocol
Phase 1 — Diagnostic Load Modification
Biomechanical Assessment: Utilizing digital dynamometry during our Comprehensive Biomechanical Assessment to measure rate-of-force development and identify where the motor recruitment sequence breaks down.
De-escalation: Temporarily removing high-velocity, maximal-effort lifting to stop the cycle of protective muscle guarding and facet joint irritation.
Phase 2 — Neuromuscular Re-Education & Pelvic Fortification
Pressure Biofeedback Training: Using a stabilizer pressure cuff set to $40\text{ mmHg}$ beneath the lumbar spine to isolate and activate the deep transversus abdominis without compensatory rectus abdominis clenching.
Low-Threshold Activation: Performing DeadBug progressions to force the nervous system to recruit small motor units before moving the extremities.
Phase 3 — Mechanics Correction & Progression
Integrating the Size Principle: Moving from isolated floor drills to closed-chain functional movements (like goblet squats and hip hinges) while maintaining the subconscious feedforward brace.
Spinal Decompression: Applying Maitland joint mobilizations to clear any lingering facet joint stiffness caused by previous compensatory spasms.
Phase 4 — Return-to-Activity Strategy (HSR)
Heavy Slow Resistance (HSR): Re-introducing heavy barbell deadlifts and squats using a $3\text{-second}$ concentric and $3\text{-second}$ eccentric tempo at $75\%\text{--}85\%\text{ 1RM}$ (HSR Protocol Details).
Athletic Inoculation: Ensuring the core automatically pressurizes under heavy, real-world loads on our Queen West turf track without conscious thought.
7. Related Conditions We Treat
Sacroiliac Joint (SIJ) Dysfunction
8. Related Blogs
High Load Low Reps: The Science of True Strength and Neuromuscular Drive (Part 1 of 3)
The Transversus Abdominis Link: Curing Gluteal Amnesia (Part 2 of 3)
Clinical Electromyography (EMG): Assessing Neuromuscular Motor Drive (114 of 550 - Glossary Series)
Anticipatory Core Control: The Biomechanics of Feedforward Bracing (141 of 550 - Glossary Series)
The Role of a Back Brace: Lumbar Stabilization & Core Integration (28 of 550 - Glossary Series)
9. Services Used in Treatment
Myofascial Release
Radial Shockwave Therapy
Gait Retraining
10. FAQ Section
What is Henneman's Size Principle? It is a neurological rule stating that the brain recruits motor units in order of size, starting with the smallest, endurance-focused fibers for stability, and progressing to the largest, power-focused fibers for heavy lifting.
How does physical therapy assist in managing core timing issues? Physiotherapy at our clinic helps reduce compensatory muscle spasms, supports the recovery of delayed neural pathways, and utilizes biofeedback to optimize the sequence of muscle recruitment.
Why do I get a sharp catch in my back when lifting light objects? When your deep core stabilizers fail to fire first (a breakdown in the size principle), your spine lacks its protective brace, allowing micro-movements that can pinch joint tissues and trigger a catch.
Can sitting at a desk all day affect how my muscles fire? Yes. Prolonged sitting can inhibit small postural motor units, making it difficult for your brain to activate them automatically when you transition to standing or lifting.
How do you support recovery of the feedforward core brace? We use specific, low-threshold exercises like the DeadBug to train the brain to fire the deep transversus abdominis automatically before your arms or legs move.
Why shouldn't I just squeeze my abs as hard as possible when lifting? Conscious, maximal clenching bypasses the natural recruitment order and often causes breath-holding, which increases pressure unevenly rather than providing a stable, subconscious biological corset.
Can optimizing motor recruitment help reduce lower back fatigue? Yes. By ensuring the correct muscles fire at the correct time, we help reduce the mechanical overload on your lower back, optimizing your movement efficiency.
What is the Rehab Mechanics approach to neuromuscular stability? We conduct a comprehensive biomechanical assessment to map your movement faults, use precise neuromuscular re-education to restore proper firing sequences, and progressively build your capacity with heavy strength training.
11. How Physiotherapy Helps
Optimizing the neurological sequencing of motor unit recruitment based on Henneman's Size Principle
Reducing mechanical overload and sheer stress on lumbar facet joints
Strengthening deep stabilizers like the transversus abdominis and multifidus via biofeedback training
Correcting pelvic drop and restoring lumbopelvic neutrality
Helping reduce compensatory global muscle spasms by down-regulating the nervous system
Improving movement efficiency and athletic power transfer using HSR loading protocols
12. CTA — Contact Us Today
Contact Us Today — All you have to lose is the pain. Stop letting uncoordinated muscle firing, unexpected back catches, and poor core timing disrupt your training and daily life. Book a comprehensive Full-Body Biomechanical Assessment with our clinical team today. Located inside the Prime Medical Centre at 68 Abell Street, Queen West. Email: info@rehabmechanics.com | Phone: (416) 533-3900
About the Author
Mr. Sanjay Attwala (B.Sc., M.Sc., RPT) is a Registered Physiotherapist, clinical director, and the founder of Rehab Mechanics in Toronto. With over 15 years of registered clinical practice and a deep specialization in complex musculoskeletal rehabilitation, Sanjay synthesizes rigorous international academic training with advanced evidence-based therapeutics to guide his clinical practice and patient education initiatives.
Academic Background & Credentials
Master of Science (M.Sc.) in Physiotherapy – University of Keele, United Kingdom (2010).
Bachelor of Science (B.Sc.) – University of Waterloo, Ontario, Canada.
Registered Physiotherapist (RPT) – Regulated health professional in excellent standing with the College of Physiotherapists of Ontario (CPO).
Corporate Entity – Operating officially under the S. Attwala Physiotherapy Professional Corporation with a DBA of Rehab Mechanics.
Clinical Expertise & Philosophy
Sanjay’s clinical approach rejects passive symptom management in favor of identifying underlying biomechanical root causes. His diverse expertise spans advanced manual therapies, personalized corrective exercise prescription, and modern physical modalities. At the Rehab Mechanics Toronto Queen West clinic, a routinely diagnoses and treats complex conditions including:
Spinal & Discogenic Pathology – Cervical, thoracic, and lumbar disc injuries, sciatica, and sacroiliac joint (SIJ) dysfunction.
Upper & Lower Extremity Injuries – Rotator cuff tears, frozen shoulder, tennis/golfer’s elbow, carpal tunnel syndrome, and complex ankle/foot pathologies.
Perinatal & Pelvic Health Rehabilitation – Specialized assessment and rehabilitation protocols tailored specifically for women during pregnancy and the post-partum period, addressing pelvic girdle pain, diastasis recti, and core stabilization.
Specialized Rehabilitation – Pelvic health therapy, TMJ dysfunction, post-surgical rehabilitation (including Total Hip and Total Knee Replacements), and custom orthotics dispensing.
Shockwave Therapy: with advanced cutting edge technological devices to suit your needs.
Interdisciplinary Practice & Patient Care
Sanjay practices an integrated model of healthcare, working closely alongside medical doctors inside the Prime Medical Centre on Abell Street to streamline patient recovery pathways. He maintains a human-centric, communication-first clinical framework, ensuring that care remains fully customized rather than automated. His clinical caseload encompasses a broad operational spectrum under Ontario's regulatory frameworks, including:
Motor Vehicle Accident (MVA) Claims – Rehabilitation navigating Ontario’s statutory accident benefits schedule.
Workplace Safety and Insurance Board (WSIB) – Occupational injury management and return-to-work screening.
Extended Health Care (EHC) & Private Practice – Multi-tier insurance coordination and long-term athletic development plans.
Commitment to Research & Community
Outside of his clinical caseload at Rehab Mechanics and his additional practice affiliations in Etobicoke, Sanjay is an active health writer and community educator. He translates contemporary peer-reviewed medical research into accessible, actionable guidance on his professional blog. As a dedicated father and husband, he mirrors his professional advice in his personal life, focusing on structural mobility, cross-training, and longevity to help his family and his community thrive. Naturally he takes he a keen interest in rehabilitation for women who are pregnant and post-partum.
Disclaimer:
The information provided on this blog is intended for educational and informational purposes only. It does not constitute medical advice, diagnosis, or a treatment plan. Always seek the direct advice of a Registered Physiotherapist, physician, or other qualified health provider regarding any medical condition or physical rehabilitation routine.
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