Learning Resources

Electrophysical Agents – Clinical Guide

Electrophysical Agents

Clinical Guide for Physiotherapy Practice

Mechanisms • Indications • Contraindications

Quick Links

Overview of Electrophysical Agents

TENS

Pain management through electrical stimulation

NMES/FES

Muscle strengthening and functional restoration

Ultrasound

Tissue healing through mechanical vibration

Laser Therapy

Cellular healing through light energy

Shortwave Diathermy

Deep heating through electromagnetic energy

Interferential

Pain relief through medium-frequency currents

Shockwave

Tissue regeneration through acoustic waves
Back to top ↑

TENS (Transcutaneous Electrical Nerve Stimulation)

How it Works

  • Gate Control Theory: Stimulates large diameter sensory fibres (A-beta) that “close the gate” to pain signals
  • Endogenous Opioid Release: Low frequency TENS may stimulate endorphin release
  • Parameters: Frequency 1-100Hz, pulse width 50-250μs

When to Use (Indications)

  • Chronic pain conditions
  • Acute post-operative pain
  • Musculoskeletal pain
  • Neuropathic pain
  • Labour pain

When NOT to Use (Contraindications)

  • Pacemaker/ICDs: Risk of interference
  • Pregnancy: Avoid over abdomen/pelvis
  • Impaired sensation: Risk of tissue damage
  • Over carotid sinus: Risk of hypotension
  • Epilepsy: Avoid near head/neck
  • Active cancer: Contraindicated over tumour sites
Memory Tip: TENS = Pain relief, but think “PEACE” – Pacemaker, Epilepsy, Active cancer, Carotid, Expectant mothers (pregnancy)
Back to top ↑

NMES/FES (Neuromuscular/Functional Electrical Stimulation)

How it Works

  • Motor Unit Recruitment: Stimulates motor nerves to cause muscle contractions
  • Strength Training: Forces muscle contractions when voluntary control is impaired
  • Parameters: Higher intensity than TENS, 20-50Hz, 200-400μs pulse width
  • FES Difference: Timed to assist functional movements (walking, reaching)

When to Use (Indications)

  • Muscle weakness/atrophy
  • Post-stroke rehabilitation
  • Spinal cord injury
  • Post-surgical muscle re-education
  • Prevention of muscle wasting
  • Improved circulation in paralyzed limbs

When NOT to Use (Contraindications)

  • Pacemaker/ICDs: Risk of interference
  • Pregnancy: Avoid over abdomen/pelvis
  • Active infection: Local or systemic
  • DVT/thrombosis: Risk of embolism from muscle pumping
  • Malignancy: Avoid over tumour sites
  • Unstable fractures: Risk of displacement
Memory Tip: NMES builds “MUSCLE” – Malignancy contraindicated, Unstable fractures, Systemic infection, Clots (DVT), Life-support devices, Expectant mothers
Back to top ↑

Ultrasound Therapy

How it Works

  • Thermal Effects: Deep heating at 3-5°C increase in tissue temperature
  • Non-thermal Effects: Acoustic streaming, cavitation, mechanical vibration
  • Tissue Healing: Increases collagen synthesis, protein synthesis, blood flow
  • Frequencies: 1MHz (deeper, 3-5cm) vs 3MHz (superficial, 1-2cm)

When to Use (Indications)

  • Soft tissue injuries (ligaments, tendons, muscles)
  • Joint contractures
  • Scar tissue adhesions
  • Chronic inflammation
  • Wound healing
  • Plantar fasciitis

When NOT to Use (Contraindications)

  • Pregnancy: Especially over abdomen/pelvis
  • Malignancy: Risk of metastasis
  • Infection: May spread infection
  • DVT: Risk of embolism
  • Impaired sensation: Risk of burns
  • Pacemaker: Over thorax only
  • Eyes, heart, reproductive organs
  • Growth plates in children
Memory Tip: Ultrasound “HEATS” but avoid “MAGIC” areas – Malignancy, Active infection, Growth plates, Impaired sensation, Clots (DVT)
Back to top ↑

Laser Therapy (Low-Level Laser/LLLT)

How it Works

  • Photobiomodulation: Light energy absorbed by mitochondria
  • ATP Production: Increases cellular energy production
  • Anti-inflammatory: Reduces prostaglandins and inflammatory mediators
  • Pain Relief: Blocks nerve conduction, releases endorphins
  • Tissue Repair: Stimulates collagen synthesis and cell proliferation

When to Use (Indications)

  • Wound healing
  • Acute and chronic pain
  • Soft tissue injuries
  • Arthritis
  • Nerve injuries
  • Post-surgical healing

When NOT to Use (Contraindications)

  • Eyes: Direct irradiation can cause retinal damage
  • Pregnancy: Unknown effects on fetus
  • Malignancy: May stimulate tumour growth
  • Photosensitive patients: Those on photosensitizing drugs
  • Direct irradiation of pacemaker
  • Areas of hemorrhage
Memory Tip: Laser “LIGHTS” up healing but “POWER” safety first – Pregnancy, Open hemorrhage, Where cancer exists, Eyes protected, Reactions to light drugs
Back to top ↑

Shortwave Diathermy

How it Works

  • Electromagnetic Heating: 27.12 MHz radio waves create deep tissue heating
  • Conversion to Heat: Electromagnetic energy converted to thermal energy in tissues
  • Deep Penetration: Heats tissues 3-5cm deep
  • Increased Circulation: Vasodilation, increased metabolism

When to Use (Indications)

  • Deep heating of muscles and joints
  • Joint contractures
  • Chronic arthritis
  • Muscle spasm
  • Chronic pain conditions
  • Pre-exercise warm-up in chronic conditions

When NOT to Use (Contraindications)

  • Metal implants: Risk of burns from heating
  • Pacemaker/ICDs: Risk of interference
  • Pregnancy: Especially abdomen/pelvis
  • Malignancy: May increase metastasis
  • Impaired sensation: Risk of burns
  • DVT: Increased circulation risk
  • Acute inflammation/infection
  • Eyes, testes, growing epiphyses
Memory Tip: Shortwave creates “HEAT” but avoid “IMPACT” – Implants (metal), Malignancy, Pacemaker, Active inflammation, Clots (DVT), Thermoregulation impaired
Back to top ↑

Interferential Therapy

How it Works

  • Beat Frequencies: Two medium-frequency currents (4000Hz) interfere to create low-frequency beat
  • Deeper Penetration: Medium frequency has less skin resistance than low frequency
  • Pain Relief: Gate control mechanism, endorphin release
  • Muscle Stimulation: Can stimulate muscle contractions at low beat frequencies

When to Use (Indications)

  • Chronic and acute pain
  • Muscle spasm
  • Joint stiffness
  • Improved circulation
  • Reduction of swelling
  • Post-operative pain

When NOT to Use (Contraindications)

  • Pacemaker/ICDs: Risk of interference
  • Pregnancy: Over abdomen/pelvis
  • Malignancy: Over tumour sites
  • DVT: Risk of embolism
  • Impaired sensation: Risk of tissue damage
  • Infection: Local or systemic
  • Over carotid sinus
Memory Tip: Interferential creates “WAVES” but watch “SPICE” – Sensation impaired, Pacemaker, Infection, Clots (DVT), Expectant mothers
Back to top ↑

Shockwave Therapy (ESWT)

How it Works

  • Acoustic Waves: High-energy sound waves create mechanical stress
  • Microtrauma: Controlled tissue damage stimulates healing
  • Neovascularization: Promotes new blood vessel formation
  • Pain Relief: Hyperstimulation theory, substance P reduction
  • Tissue Regeneration: Stimulates growth factors

When to Use (Indications)

  • Plantar fasciitis
  • Calcific tendinitis (shoulder)
  • Tennis/golfer’s elbow
  • Achilles tendinopathy
  • Greater trochanteric pain syndrome
  • Non-union fractures

When NOT to Use (Contraindications)

  • Pregnancy: Risk to fetus
  • Malignancy: May promote metastasis
  • Infection: Local or systemic
  • Bleeding disorders: Risk of hemorrhage
  • Pacemaker: Near thoracic area
  • Growth plates in children
  • Over major nerves/vessels
  • Lung tissue (risk of pneumothorax)
Memory Tip: Shockwave “BREAKS” up problems but avoid “PLASMA” – Pregnancy, Lung tissue, Active infection, Systemic bleeding disorders, Major vessels/nerves, Active malignancy

Universal Contraindications – Quick Reference

The “Big 5” – Nearly Universal Contraindications

  1. Pacemaker/ICDs – Risk of electrical interference
  2. Pregnancy – Unknown effects on fetus (especially abdomen/pelvis)
  3. Active Malignancy – Risk of promoting tumour growth/spread
  4. Impaired Sensation – Cannot detect tissue damage/burns
  5. Active Infection – May worsen or spread infection
Modality Key Mechanism Primary Use Unique Contraindication
TENS Gate control theory Pain relief Over carotid sinus
NMES/FES Motor unit recruitment Muscle strengthening DVT (muscle pumping risk)
Ultrasound Thermal/mechanical effects Tissue healing Over growth plates
Laser Photobiomodulation Wound healing Direct eye exposure
Shortwave Deep electromagnetic heating Deep tissue heating Metal implants (heating risk)
Interferential Beat frequency currents Pain relief Over carotid sinus
Shockwave Acoustic wave microtrauma Chronic tendinopathies Over major vessels/lung

Clinical Decision Making Framework

Pre-Treatment Checklist

Always Ask These Questions:
  1. Does the patient have a pacemaker or ICD?
  2. Is the patient pregnant?
  3. Is there any active cancer or history of cancer in treatment area?
  4. Can the patient feel normal sensation in the area?
  5. Are there any signs of infection?
  6. Does the patient have any metal implants in the area?
  7. Is there any active bleeding or clotting disorder?
  8. Are there any open wounds in the treatment area?

Red Flag Symptoms

  • Fever/systemic illness – Suggests infection
  • Unexplained weight loss – May indicate malignancy
  • Night pain – Red flag for serious pathology
  • Constant, unremitting pain – Not typical of musculoskeletal conditions
  • Recent trauma with severe pain – Rule out fracture
Clinical Pearl: When in doubt, don’t treat. Always err on the side of caution and refer for medical clearance if any contraindications are suspected.