1. Electrical Stimulation Techniques
© 2005 – FA Davis

2. Current Flow Electron Flow Ion Flow
(shown in red)
Between the generators and electrodes
To and from the generator
Ion Flow
(shown in yellow)
Occurs within the tissues
Negative ions flow towards the anode and away from the cathode
Positive ions flow towards the cathode and away from the anode + - + -

3. Electrodes Purpose Materials
Completes the circuit between the generator and body
Interface between electron and ion flow
Primary site of resistance to current
Materials
Metallic (uses sponges)
Silver
Carbon rubber
Self-adhesive

4. Electrode Size Determines the Current Density Equal size
Bipolar arrangement
Approximately equal effects under exach

5. Electrode Arrangements
Based on: Current Density Proximity to Each Other Anatomic Location (Stimulation Points)

6. Current Density Bipolar Technique Monopolar Technique
Equal current densities
Equal effects under each electrode (all other factors being equal)
Monopolar Technique
Unequal current densities
At least 4:1 difference
Effects are concentrated under the smaller electrode
“Active” electrode(s)
No effects under larger electrode
“Dispersive” electrode
Quadripolar Technique
Two bipolar electrode arrangements
Two independent electrical channels
TENS is a common example
“Active”
“Dispersive”

7. Electrode Proximity Determines the number of parallel paths
The farther apart the electrodes the more parallel paths are formed
More current is required to produce effects as the number of paths increases

8. Stimulation Points Motor Points Trigger Points Acupuncture Points
Superficial location of motor nerve
Predictably located
Motor nerve charts
Trigger Points
Localized, hypersensitive muscle spasm
Trigger referred pain
Arise secondary to pathology
Acupuncture Points
Areas of skin having decreased electrical resistance
May result in pain reduction
Traumatized Areas
Decreased electrical resistance (increased current flow)

9. Path of Least Resistance
Ion flow will follow the path of least resistance
Nerves
Blood vessels
The current usually does not flow from electrode-to-electrode (the shortest path)
The path of least resistance is not necessarily the shortest path

10. Selective Stimulation of Nerves
Nerves always depolarize in the same order
Sensory nerves
Motor nerves
Pain nerves
Muscle fiber
Based on the cross-sectional diameter
Large-diameter nerves depolarize first
Location of the nerve
Superficial nerves depolarize first

11. Phase Duration and Nerve Depolarization
Phase duration selectively depolarizes tissues
Phase Duration Tissue
Short Sensory nerves
Medium Motor nerves
Long Pain nerves
DC Muscle fiber

12. Adaptations Patients “get used” to the treatment
More intense output needed
Habituation
Central nervous system
Brain filters out nonmeaningful, repetitive information
Accommodation
Peripheral nervous system
Depolarization threshold increases
Preventing Adaptation
Vary output (output modulation) to prevent
The longer the current is flowing, the more the current must be modulated.

13. Electrical Stimulation Goals
Muscle Contractions
[Instructor Note: More detail on these techniques are found in the CH 13 ppt: Treatment Strategies]
© 2005 – FA Davis

14. Motor-level Stimulation Comparison of Voluntary and Electrically-Induced Contractions
Type I fibers recruited first
Asynchronous
Decreases fatigue
GTO protect muscles
Electrically-induced
Type II fibers recruited first
Synchronous recruitment
Based on PPS
GTOs do not limit contraction

15. Motor-level Stimulation
Parameters:
Amplitude: Contraction strength increases as amplitude increases
Phase duration: 300 to 500 µsec targets motor nerves:
The shorter the phase duration, the more amplitude required
Longer durations will also depolarize pain nerves
Pain often limits quality and quantity of the contraction
Pulse frequency: Determines the type of contraction

16. Pulse Frequency
Frequency determines the time for mechanical adaptation
Lower pps allows more time (longer interpulse interverals)
Label Range Result
Low < 15 pps* Twitch: Individual contractions
Medium pps* Summation: Contractions blend
High >40 pps* Tonic: Constant contraction
* Approximate values. The actual range varies from person-to-person and between muscle groups

17. Effect of Pulse Frequency on Muscle Contractions
1 pulse per second
Twitch Contraction
The amount of time between pulses – the interpulse interval – is long enough to allow the muscle fibers to return to their original position
20 pulses per second
Summation
The amount of time between pulses allows some elongation of the fibers, but not to their starting point.
40 pulses per second
Tonic Contraction
The current is flowing so rapidly that there is not sufficient time to allow the fibers to elongate

18. Electrical Stimulation Goals
Pain Control
© 2005 – FA Davis

19. Pain Control Sensory-level Motor-Level Noxious Level
Target A-beta fibers Motor nerves A-delta
Tissue C fibers
Phase < 60 µsec 120 to 250 µsec 1 msec
Duration
Pulse 60 to 100 pps 2 to 4 pps Variable
Frequency 80 to 120 pps
Intensity Submotor Moderate to To tolerance
Strong contraction

20. Electrical Stimulation Goals
Edema Control and Reduction
© 2005 – FA Davis

21. Edema Control Cathode placed over injured tissues High pulse frequency
Submotor intensity
Thought to decrease capillary permeability
Do not use if edema has already formed

22. Edema Reduction Muscle contractions “milk” edema from extremity
Electrodes follow the vein’s path
Alternating rate targets muscle groups
Elevate during treatment

23. Electrical Stimulation Goals
Fracture Healing
© 2005 – FA Davis

24. Fracture Healing Electrical current triggers bone growth
Piezoelectric effect within the collagen matrix
Alternating current
Applied transcutaneously
Similar to diathermy units (no heat production)
Direct current
Implanted electrodes

25. Contraindications and Precautions
© 2005 – FA Davis

26. Contraindications and Precautions
Areas of sensitivity
Carotid sinus
Esophagus
Larynx
Pharynx
Around the eyes
Temporal region
Upper thorax
Severe obesity
Epilepsy
In the presence of electronic monitoring equipment
Cardiac disability
Demand-type pacemakers
Pregnancy (over lumbar and abdominal area)
Menstruation (over lumbar and abdominal area)
Cancerous lesions (over area)
Sites of infection (over area)
Exposed metal implants