TRANSCUTANEOUS ELECTRICAL NERVE STIMULATION (TENS)
OPERATING PROCEDURE
1. Introduction
Transcutaneous Electrical Nerve Stimulation (TENS) is a non-invasive electrotherapeutic modality used extensively in physiotherapy and rehabilitation for pain modulation. It delivers controlled electrical pulses through surface electrodes to stimulate peripheral nerves, thereby reducing pain perception. TENS is valued for its safety profile, versatility, ease of application, and compatibility with active rehabilitation, making it suitable across acute, subacute, and chronic pain conditions.
TENS is symptom-modulating rather than curative; its optimal role is to reduce pain sufficiently to enable movement, exercise, and functional recovery.
2. Neurophysiological Basis of TENS
2.1 Pain Modulation Theories
a) Gate Control Theory (High-Frequency TENS)
- Preferential activation of large-diameter A-beta sensory fibers
- Inhibition of nociceptive input (A-delta and C fibers) at the dorsal horn
- Rapid onset of analgesia during stimulation
b) Endogenous Opioid Release (Low-Frequency TENS)
- Activation of descending inhibitory pathways
- Release of endorphins and enkephalins
- Analgesia persists beyond treatment duration
Conceptual Graph: Frequency vs Analgesic Mechanism
Analgesic Mechanism
│ █████████ Gate control (80–120 Hz)
│ ███████
│ █████ Endogenous opioids (1–10 Hz)
│███
└──────────────────────── Frequency (Hz)
3. Therapeutic Objectives
TENS is used to:
- Reduce acute and chronic pain
- Decrease reliance on analgesic medication
- Facilitate participation in exercise and functional activities
- Improve patient comfort and confidence
- Support self-management strategies
4. Indications
| Category | Conditions |
|---|---|
| Musculoskeletal | Low back pain, neck pain, OA |
| Neuropathic | Peripheral neuropathy, radiculopathy |
| Postoperative | Post-surgical pain |
| Chronic pain | Myofascial pain, fibromyalgia (selected cases) |
| Obstetric | Labor pain (protocol-based) |
5. Contraindications and Precautions
Absolute Contraindications
- Cardiac pacemaker or implanted defibrillator (unless cleared)
- Over carotid sinus
- Over eyes or anterior neck
- Over malignancy at treatment site
- Pregnancy (over abdomen/lumbar region)
Relative Contraindications / Precautions
- Impaired sensation
- Skin lesions or infection
- Epilepsy
- Cognitive impairment affecting safe use
6. Equipment Components
| Component | Function |
|---|---|
| TENS unit | Generates electrical pulses |
| Electrodes | Deliver current |
| Lead wires | Connect electrodes to unit |
| Control panel | Adjusts parameters |
| Power source | Battery/mains |
7. TENS Modes and Parameters
7.1 Conventional (High-Frequency) TENS
| Parameter | Typical Setting |
|---|---|
| Frequency | 80–120 Hz |
| Pulse duration | 50–80 µs |
| Intensity | Strong but comfortable sensory |
| Duration | 20–40 minutes |
Effect: Rapid, short-lasting analgesia during stimulation.
7.2 Acupuncture-Like (Low-Frequency) TENS
| Parameter | Typical Setting |
|---|---|
| Frequency | 1–10 Hz |
| Pulse duration | 150–250 µs |
| Intensity | Strong, visible muscle twitch |
| Duration | 20–30 minutes |
Effect: Slower onset, longer-lasting analgesia.
7.3 Burst TENS (Hybrid)
| Parameter | Typical Setting |
|---|---|
| Burst frequency | 1–4 bursts/sec |
| Intra-burst freq. | ~100 Hz |
| Intensity | Strong, rhythmic |
| Use | Chronic pain |
8. Electrode Placement Strategies
| Placement Method | Indication |
|---|---|
| Dermatomal | Radicular pain |
| Peripheral nerve | Localized pain |
| Pain site (bracketing) | Musculoskeletal pain |
| Acupuncture points | Chronic pain |
Principles:
- Place electrodes over intact skin
- Maintain adequate inter-electrode distance
- Avoid bony prominences
9. Pre-Procedure Preparation
Patient
- Explain purpose and expected sensation (tingling)
- Obtain consent
- Inspect skin and sensation
- Position comfortably
Equipment
- Check battery/output
- Select appropriate mode and parameters
- Prepare clean electrodes
10. Operating Procedure (Step-by-Step)
- Select Mode (high-frequency, low-frequency, or burst)
- Set Parameters (frequency, pulse width, time)
- Apply Electrodes at selected sites
- Increase Intensity Gradually to therapeutic level
- Maintain Treatment for prescribed duration
- Reassess Pain during and after stimulation
11. Monitoring During Treatment
Monitor for:
- Skin irritation
- Excessive discomfort
- Dizziness or unusual sensations
- Adequacy of analgesia
Adjust intensity periodically to prevent accommodation.
12. Post-Treatment Care
- Reduce intensity to zero before removing electrodes
- Inspect skin
- Reassess pain and function
- Educate patient on home use if prescribed
- Document session details
13. Dosage and Frequency
| Phase | Recommendation |
|---|---|
| Acute pain | Daily or multiple short sessions |
| Chronic pain | 1–3 sessions/day (home use) |
| Program duration | As needed with reassessment |
14. Integration with Rehabilitation
TENS should be used to:
- Enable early movement and exercise
- Reduce guarding during manual therapy
- Support activity pacing in chronic pain
TENS enables participation; exercise restores function.
15. Advantages and Limitations
Advantages
- Non-invasive and safe
- Patient-controlled
- Minimal side effects
- Suitable for home programs
Limitations
- Temporary analgesia
- Variable individual response
- Limited effect in some neuropathic pain states
16. Safety, Hygiene, and Quality Control
- Clean electrodes regularly
- Replace worn pads
- Avoid electrode sharing without cleaning
- Patient education on safe home use
17. Documentation Standards
Record:
- Pain site and diagnosis
- Mode and parameters
- Electrode placement
- Duration and response
18. Clinical Pearls
- Strong sensory intensity improves efficacy
- Vary parameters to reduce accommodation
- Combine with movement for sustained benefit
- Educate patients for realistic expectations
- Reassess pain mechanisms regularly
Conclusion
Transcutaneous Electrical Nerve Stimulation is a scientifically grounded, clinically versatile modality for pain modulation. When applied with appropriate parameters, correct electrode placement, and integration into active rehabilitation, TENS effectively supports pain control and functional recovery across diverse patient populations.
References
- Johnson MI. Transcutaneous electrical nerve stimulation (TENS). Pain.
- Cameron MH. Physical Agents in Rehabilitation.
- Robinson AJ, Snyder-Mackler L. Clinical Electrophysiology.
- Sluka KA, Walsh D. TENS: basic science mechanisms. J Pain.
- Kisner C, Colby L, Borstad J. Therapeutic Exercise: Foundations and Techniques.