While High TENS provides immediate, short-term pain relief by targeting A-beta fibers, "Low TENS" (Acupuncture-like TENS) is utilized for chronic, stubborn pain syndromes. Physiotherapy assists in managing this chronic pain by utilizing low-frequency, high-intensity electrical currents to help optimize movement. The biomechanical and neurological root cause of this relief is the deliberate stimulation of smaller A-delta motor and sensory fibers. This intense stimulation forces the brain (specifically the hypothalamus) to release endogenous opioids—powerful, natural endorphins that provide profound, long-lasting systemic pain relief.
The Patient’s Story / Toronto Context
In Part 1, we learned how "High TENS" acts like a fast-acting neurological off-switch, utilizing high frequencies to stimulate A-beta fibers and close the pain gate for acute injuries like a fresh ankle sprain in Trinity Bellwoods.
However, not all pain is acute. Many active professionals in Toronto's Financial District suffer from chronic, deep-seated musculoskeletal issues—like persistent lower back pain that has lingered for years, or severe, stubborn knee osteoarthritis that makes climbing the stairs at the TTC an agonizing daily chore.
When these patients try High TENS, they often report that the buzzing feels pleasant, but the moment they turn the machine off, the deep, chronic ache returns instantly. They arrive at Rehab Mechanics frustrated, asking, "Is there a way to get pain relief that actually lasts longer than the treatment itself?"
At our clinic, we educate patients that chronic pain requires a different neurological strategy. We must stop trying to simply "block" the pain at the spinal cord and instead force the brain to manufacture its own heavy-duty painkillers. By switching the parameters to "Low TENS" (Acupuncture-like TENS), specialized physical therapy can assist in managing your chronic pain. We teach you how to use a slow, intense electrical pulse to trigger a massive release of natural endorphins, providing a deep, systemic wave of relief that lasts for hours after you leave the clinic.
Structural / Biomechanical Analysis
To understand why a slow, intense electrical pulse creates long-lasting pain relief, we must perform an analysis of motor nerve activation, the body's internal pharmacy, and the descending pain inhibition pathways.
Shifting the Target: A-Delta and Motor Fibers
High TENS targets the large, superficial A-beta (touch) fibers. "Low TENS" completely shifts the electrical target.
The Parameters: Low TENS (often called Acupuncture-like TENS or AL-TENS) uses a very low frequency (typically 1 to 10 Hz) but a much higher intensity.
The Activation Threshold: The intensity is turned up significantly higher than High TENS—right to the edge of the patient's tolerance limit. This massive electrical push bypasses the superficial touch receptors and aggressively stimulates the deeper A-delta sensory fibers and the motor nerves.
The Physical Response: Because the motor nerves are activated at a low frequency, the patient will experience strong, visible, and rhythmic muscle twitches (contractions) under the electrode pads.
The Endogenous Opioid System (The Brain's Pharmacy)
Why do we want to cause these strong muscle twitches and stimulate the deeper A-delta fibers? It is a biological hack to trigger the brain's emergency pain-relief system.
The Hypothalamic Trigger: The intense, pulsing signal from the A-delta fibers travels up the spinal cord and directly stimulates the hypothalamus and the periaqueductal gray (PAG) region in the brain.
The Endorphin Release: Believing the body is under significant, sustained stress (mimicking the effects of intense acupuncture or heavy physical exertion), the brain commands the release of endogenous opiates, specifically beta-endorphins.
Descending Inhibition: These natural endorphins flood the central nervous system, binding to opioid receptors throughout the brain and spinal cord (descending inhibition). This profoundly dampens the perception of pain on a systemic level.
The Clinical Advantage: Delayed Onset, Prolonged Offset
The biological mechanics of Low TENS create a distinctly different therapeutic timeline than High TENS.
Because it takes time for the brain to synthesize and release endorphins into the bloodstream, the pain relief from Low TENS is delayed (often taking 20 to 30 minutes of continuous stimulation to reach maximum effect).
However, once those natural opioids are circulating, they remain active in the system for hours. The patient experiences deep, profound pain relief that lasts long after the 30-minute clinical session has ended.
Clinical Red Flags
Low TENS involves high-intensity stimulation that causes visible muscle contractions. We meticulously screen patients to ensure this aggressive mechanical pumping is safe for their specific tissue state:
Acute Tissue Tearing or Fractures: Low TENS is strictly contraindicated for fresh, acute injuries (like a torn muscle or unhealed fracture). The strong, involuntary muscle twitches caused by the electrical current will violently pull on the fragile, healing tissues, causing severe re-injury.
Severe Allodynia / Hyperalgesia: Patients suffering from Complex Regional Pain Syndrome (CRPS) or severe central sensitization may find the high intensity of AL-TENS agonizing, as their nervous system incorrectly interprets the strong electrical pulses as excruciating tissue damage.
Cardiac Pacemakers or Defibrillators: As with all TENS modalities, application is strictly banned in patients with implanted cardiac devices due to the risk of lethal electrical interference.
Loss of Sensation (Neuropathy): If a patient has severe diabetic neuropathy and cannot feel the electrical current, they are at high risk of turning the intensity up too high and causing severe electrical burns or muscle damage without realizing it.
Primary Source Proof (PubMed / NIH)
Clinical neurophysiology and pain management literature confirms that low-frequency, high-intensity TENS (Acupuncture-like TENS) activates A-delta and motor efferent fibers, stimulating the release of endogenous opioids (beta-endorphins) and engaging descending pain inhibitory pathways, providing prolonged relief for chronic musculoskeletal pain.
Review the Clinical Evidence on PubMed: Transcutaneous Electrical Nerve Stimulation (TENS): A Possible Aid for Pain Relief (National Institutes of Health)
Review the Clinical Evidence on PubMed: Mechanisms of Action of Transcutaneous Electrical Nerve Stimulation (TENS) (National Institutes of Health)
Review the Clinical Evidence on PubMed: Endogenous Opioid Release and Acupuncture-Like TENS in Chronic Pain Management (National Institutes of Health)
The Rehab Mechanics Corrective Protocol
We utilize Low TENS as a strategic tool to manage chronic, unrelenting pain, creating the long-lasting relief required to pursue heavy structural rehabilitation.
Phase 1 — Load Modification (The Endorphin Flush): For a patient with chronic lower back osteoarthritis, we apply Low TENS (AL-TENS) for 20 to 30 minutes prior to their active workout. We turn the intensity up to produce strong, comfortable muscle twitches. This forces the brain to release a massive wave of natural endorphins.
Phase 2 — Pelvic Fortification (The Analgesic Window): Once the deep, systemic pain relief sets in, we capitalize on the prolonged "offset" time. The patient transitions to the gym floor to perform heavy core stabilization and pelvic fortification exercises. The chronic ache that usually stops them is heavily muted by the circulating endorphins.
Phase 3 — Gait Retraining / Mechanics Correction: We use the analgesic window to correct long-standing compensatory limps. If chronic hip pain has caused a patient to alter their walking stride for years, the deep relief provided by AL-TENS allows the nervous system to finally trust the injured leg again, allowing for seamless gait retraining.
Phase 4 — Return-to-Activity Strategy (Electrode Mapping): To maximize the effectiveness of these treatments, the electrical current must be delivered precisely. In Part 3, the final installment of this series, we will detail "Electrode Placement Strategies," explaining the clinical biomechanics of targeting dermatomes, motor points, and specific nerve pathways for ultimate pain relief.
Related Conditions We Treat
Chronic Osteoarthritis (Knee, Hip, Spine)
Chronic Lower Back Pain
Fibromyalgia
Chronic Myofascial Pain Syndrome
Primary Dysmenorrhea (Menstrual Pain)
Frozen Shoulder (Adhesive Capsulitis)
Related Blogs
The Physiology of Pain Relief: How High TENS Tricks Your Nervous System (Part 1 of 3)
Electrode Placement Strategies: Targeting Dermatomes and Nerve Roots (Part 3 of 3)
Dry Needling vs. Acupuncture: Understanding the Biomechanical Difference
Marma Points Meets Neuromuscular Trigger Points: The Anatomy of Pain Relief
Services Used in Treatment
Electrotherapy (Low TENS / AL-TENS)
Holistic Pain Management Integration
Biomechanical Movement Assessments
Neuromuscular Re-Education
Strengthening Programs
Gait Retraining
FAQ Section
Can physiotherapy assist in managing chronic arthritis pain using TENS? Yes. Physiotherapy supports recovery by utilizing Low TENS to help optimize movement. This specific setting forces the brain to release natural, long-lasting painkillers (endorphins), making chronic arthritis pain much more manageable during daily activities.
What is the difference between High TENS and Low TENS? High TENS uses fast impulses to block pain at the spinal cord quickly, but the relief stops when the machine turns off. We assist in managing chronic pain by using Low TENS (slow, intense impulses), which causes muscle twitching and triggers a long-lasting release of endorphins from the brain.
Why do my muscles twitch when the physiotherapist uses Low TENS? Low TENS uses a high intensity and low frequency specifically designed to activate motor nerves. We optimize movement by ensuring you feel these strong, visible muscle twitches, as they are the exact mechanical trigger required to signal the brain to release endorphins.
Is it supposed to hurt when the muscles are twitching? No. While the intensity must be high and the twitching must be strong, it should remain at a "strong but comfortable" sub-noxious level. We carefully monitor the intensity to ensure it never crosses into sharp, tearing pain.
Why does it take 20 minutes for Low TENS to work? Because it relies on the brain synthesizing and releasing hormones (endorphins) into your bloodstream, the biological process takes time. We help address contributing factors of impatience by educating patients on this delayed, but ultimately superior, timeline for chronic pain.
Can I use Low TENS on a fresh, acute muscle tear? Absolutely not. The strong muscle twitches will actively pull on and further tear the fresh injury. We safely integrate High TENS for acute injuries and save Low TENS strictly for chronic, structurally stable conditions.
Does Low TENS work the same way as acupuncture? Yes, the neurological mechanism is very similar. Acupuncture-like TENS (AL-TENS) stimulates the same deep sensory fibers that a twisting acupuncture needle does, utilizing electrical current rather than physical needles to trigger the descending pain inhibition pathways.
How long will the pain relief last after the treatment? Because the endorphins remain circulating in your system, the profound pain relief from a 30-minute Low TENS session can last for several hours. We utilize this extended analgesic window to perform targeted physical rehabilitation.
How Physiotherapy Helps
Reducing tissue irritation by triggering a massive, systemic release of endogenous opioids
Correcting pelvic drop and postural limps by profoundly muting chronic, long-standing joint aches
Improving cadence and walking mechanics by providing hours of sustained, post-treatment analgesia
Strengthening stabilizers via heavy loading performed during the prolonged endorphin window
Reducing mechanical overload on a central nervous system exhausted by chronic pain signals
Improving foot mechanics by alleviating the chronic, burning pain of conditions like severe plantar fasciitis
CTA — Contact Us Today
Contact Us Today — All you have to lose is the pain Stop letting chronic pain dictate your life. Book a comprehensive biomechanical and electrotherapy assessment with our clinical team today to learn how to activate your body's natural painkillers. 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, he 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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