1. Electrical Muscle Stimulation
ESAT 3640
Therapeutic Modalities

2. Principles of Electricity

3. Electrical Modalities
Electricity and water don’t mix. Right?
Wrong! At least in the case of electricity as a stimulating current
“To understand how current flow effects biological tissue, you must first be familiar with some of the principles that describe how electricity is produced and how it behaves in an electrical circuit”

4. Components of Electrical Current
Ions
Tend to move from an area of higher concentration to an area of lower concentration
Electrical force creates electrical potentials
The more ions present, the greater the potential
(+) and (-) charged particles
Contain electrical energy – have ability to move
Electrical force is capable of propelling particles from higher to lower energy levels establishing electrical potentials
Electrical potentials – difference between charged particles at a higher and lower potential

5. Components of Electrical Current continued
Electrons
Electrical current
Flow of electrons is always from high potential to low potential
Ampere
Coulomb
Coulombs Law
(-) charged particles
Net movement of electrons within a conducting medium
4. Rate of electrical current flow
Indicates number of electrons in current
1 amp is movement of 1 coulomb (6.25 x 1018 electrons) per second
Modalities are typically
Milliamps = 1/1000 amp
Microamps = 1/1,000,000 amp

6. Components of Electrical Current continued
Electrons will not move unless an electrical potential difference in the concentration of these charged particles exists between 2 points
Electromotive force (volt)
Voltage
110 V or 220 V
Must be applied to produce movement of electrons
Difference in electron populations between points
Ex. 1.5 volt
Force resulting from an accumulation of electrons at one point in an electrical circuit.
Usually corresponds to a deficit of electrons at another point in the circuit
Suitable conductor between 2 points needed to create electron movement from high to low
Battery example
Modalities will modify voltage from volts to millivolts

7. Components of Electrical Current continued
Path of least resistance
Conductors
Insulators
Resistance
Ohm’s law
Permit free movement
Metals – large number of free electrons that are given up asily
Resists current flow
Contain few free electrons = greater resistance to flow – wood, air, glass
Impedance – opposition to electron flow in a conducting media (ohm)
Increased resistance = decreased flow
Current in electrical circuit is directly proportional to the voltage and inversely proportional to resistance
Current flow = voltage/resistance

8. Electrotherapeutic Currents
Direct (DC)
Monophasic
Alternating (AC)
Biphasic
Pulsed
Polyphasic
Unidirectional flow from (-) pole to (+) pole
Change in direction requires off time
Change in direction; change in polarity
Grouped pulses interrupted for short period of time, repeated at regular intervals
IFC, Russian

9. Direct Current

10. Alternating Current

11. Pulsed Current

12. Generators of Electrotherapeutic Currents
Regardless of current type, all are transcutaneous electrical stimulators
TENS
Transcutaneous electrical nerve stimulator
NMES (EMS)
Neuromuscular electrical stimulator
MENS
Microcurrent electrical nerve stimulator
Electrotherapeutic currents are all transcutaneous electrical stimulators (pads to skin)
TENS
Neuromuscular
MENS

13. Generators of Electrotherapeutic Currents continued
No relationship between the type of current being delivered by the generator and the type of current used as a power source for the generator

14. Components of Electrical Generator
Transformer
Rectifier
Filter
Regulator
Amplifier
Oscillator
Reduces the amount of voltage from the power supply
Converts AC current to pulsating DC current
Changes pulsating DC to smooth DC
Produces a specific controlled voltage output
Used to magnify or increase the amplitude of the voltage output of the generator and control it at a specific level
Used to produce and output a specific waveform, which may be different from that used to power or drive the stimulating unit

15. Waveforms
Graphic representation of the shape, direction, amplitude, duration, and pulse frequency of the electrical current being produced by the electrotherapeutic device, as displayed by an oscilloscope

16. Sine Wave
Rolling

17. Rectangular Wave Sharp rise, levels off, sharp decline
Also referred to as square waves

18. Triangular Wave Fairly sharp rise; no leveling off, sharp decline
Also called spiked

19. Pulse, Phase, Direction of Current Flow
Pulse – Individual waveform
Phase – portion of the pulse that rises above or below the baseline for some period of time
Monophasic
Biphasic
Ployphasic
One phase in each pulse
2 phases
3 or more grouped phases in 1 pulse
IFC, Russian

20. Pulse Intervals
Interpulse interval – Interruptions between individual pulses or groups of pulses
Intrapulse interval – Period of time between individual pulses
2. Associated with polyphasic current

21. Pulse Amplitude
Amplitude – Intensity of current flow as indicated by the height of the waveform from baseline
Amplitude = Voltage = Current intensity
Higher the amplitude; the greater the peak voltage or intensity
Because of intervals, avg. current is low (interpulse period = 0)
2-100 milliamps
Increase pulse duration or pulse frequency or combo of both

22. Phase Charge Total amount of electricity delivered during each pulse
Monophasic always greater than zero
Biphasic is = to the sum of the phase charges
Symmetrical = zero
Asymmetrical = net pulse charge is greater than zero
Asymmetrical by definitions is DC current

23. Rise and Decay Times
Rate of rise – How quickly a waveform reaches its maximum amplitude
Decay time – Time required for a waveform to go from peak amplitude to zero volts
Rate of rise and accommodation
More rapid the rate of rise, the greater the currents ability to excite nervous tissue
Constant level of stim = accomodation
High peak intensity with short-phase duration produces comfortable type of current; effective stimulation of sensory, motor and pain fibers

24. Pulse Duration
Duration of each pulse indicates the length of time current is flowing in one cycle
Monophasic – phase duration = pulse duration
Biphasic – pulse duration is determined by the combined phase durations
Pulse period – Combined time of the pulse duration and the interpulse interval
Pulse width

25. Pulse Frequency Indicates the number of pulses per second
Increase in frequency, amplitude tends to increase and decrease more rapidly
Muscular and nervous system responses depend on the length of time between pulses and on how the pulses or waveforms are modulated
One to several hundred pulses per second
Below 50 pulses/sec = twitch contractions
At 50 pulses/sec or greater = tetanic contraction occurs

27. Stimulators Clinically speaking
Low frequency generators
Medium frequency generators
High frequency generators
In general, all stimulators are low-frequency generators
Medium/High generators claim to have frequencies of 2500 to pulses per second
Actually groups of pulses combined as bursts (combined set of three or more pulses; also referred to as packets or envelopes) that range in frequency from pulses per second

28. Current Modulation
Continuous – Amplitude of current remains same for several seconds or minutes
Interrupted – on time, off time
Burst – combined set of 3 or more pulses
Ramped – current builds gradually to some maximum amplitude
Iontophoresis works this way
Muscle reeducation, strength training, increase ROM
Muscle contraction

29. Series Circuit
Circuit in which there is only one path for current to get from one terminal to another
Components are placed end to end
Resistance to flow is = to the resistance of all the components in the circuit added together
RT = R1 + R2 +R3
Voltage decreased at each component
VT = VD1+VD2+VD3
High resistance = low voltage
Large voltage needed to drive current

30. Series Circuit

31. Parallel Circuit
A circuit in which 2 or more routes exist for current to pass between the two terminals
Component resistors are side by side, and the ends are connected
Same voltage to each resistor
Current flow depends on resistance at each component

32. Parallel Circuit
Total voltage is exactly same as voltage at each component
VT =V1=V2=V3
Adding alternative pathway improves ability of current to flow from one point to another
Path of least resistance
Resistance and Ohm’s law
1/RT = 1/R1+1/R2+1/R3
More pathways = decreased resistance
Current flow = voltage/resistance

33. Parallel Circuit

34. Circuits Series have higher resistance and less current flow
Parallel have lower resistance and higher current flow

35. Electrical Modalities
Make use of combined series and parallel circuits
Current through skin = series circuit
Once through skin and fat, current comes into contact with many other tissues
Parallel circuit

36. Body Circuit

37. Electric Stimulation Currents

38. Electrodes Electrode-skin interface Conducting mediums Electrode size
Conversion of flow electrons to flow of ions
Water, gels
Size inversely affects density of current
As size of electrode decreases, the current density increases

39. Electrode Placement Stimulation points Bipolar technique
Motor
Trigger
Acupuncture
Bipolar technique
Monopolar technique
Quadripolar Technique
Bipolar tech. – current density is approx. = under each pad
Monopolar tech. – 1 active, 1 dispersive, current density higher under one pad (usually active)
Quadripolar – 4 pads, two channel

40. Current Flow Through Biologic Tissue
Current flow through path of least resistance
Tissue high in water content = high ion content = best conductor of electricity
Skin is insulator
The greater the impedance of the skin, the more voltage needed
Blood is best conductor

41. Physiologic Responses to Electrical Currents
Electricity will have an effect on each cell and tissue that is passes through
Type and extent of response dependent on:
1) Type of tissue and its response characteristics
2) Nature of the current applied
Skin impedance

42. Goals of Electric Stimulation
Muscle contraction
Pulse amplitude
Pulse frequency
Phase duration
Pain control
Control and reduction of edema
Sensory-level stimulation
Motor-level stimulation
Decrease effect of atrophy, muscle reeducation, reduce edema, strength augmentation
Increase amplitude = increase contraction
Less than 50 p/s = twitch, 50 or greater = tetany
Motor nerve – moderate phase duration
Decrease pressure on nerve, decrease muscle spasm, eliminate mechanical and chemical mediators of pain
Affect transmission of pain
Control and reduction of edema
Stop formation of edema by preventing fluids from escaping into surrounding tissue
Sensory level is just that. Reduction in capillary pressure and capillary permeability discourages plasma proteins from entering extracellular tissues
Assist venous and lymphatic return
Motor level = muscle pump

43. Goals Continued Wound healing Strength augmentation Fracture healing
Increased hydration, increased # of growth factor receptors, increased rate of collagen formation, stimulates growth of fibroblasts and granulation tissues, reduces # of mast cells present
Russian wave
Body does not recognize difference from one healing current and one introduced from outside

44. TENS Transcutaneous Electrical Nerve Stimulation
Process of altering the perception of pain through the use of an electrical current
Gate theory
Endogenous opiate
Setup dependent

45. TENS
Pain reduction is primarily through modulation of the nervous system
May activate the preganglionic and postganglionic neurons, causing mild vasoconstriction
Caffeine warning
Caffeine warning
200 mg (2-3 cups) decreases effectiveness
Competes with adenosine for receptor sites
Adenosine – primary mediator of TENS induced pain reduction
Caffeine binds to site --- adenosine can’t --- decreases effectiveness of TENS

46. TENS Only alters perception of pain
Little effect on the underlying pathology
Use with other therapies that attempt to treat source of pain
Manual exercise

47. High Frequency TENS Sensory level High pulse frequency
60 – 100 pps
Short pulse duration
Less than 100  sec
Activates gate pain modulation at spinal cord level
Stimulation of large diameter sensory nerve fibers
 = micro
Works on gate control mechanisms

48. High Frequency TENS Accomodation is concern with long term use
Current modulation can diminish accomodation
Burst & frequency modulation

49. High Frequency TENS Effective for:
Pain associated with musculoskeletal disorders
Post operative pain
Inflammatory condition
Myofascial pain
Myofascial pain = musculoskeletal pain
Trigger points
Fibromyalgia = chronic inflammation of muscle or connective tissues

50. Low Frequency TENS Motor level Low pulse frequency Long pulse duration
2 – 4 pps
Long pulse duration
150 – 250  sec
45 minute treatment time
Beta endorphin release

51. Low Frequency TENS
Activates small diameter nociceptors and motor fibers
Release of -endorphin
Results in narcotic like pain reduction
Stimulates pituitary gland
Release of chemicals that trigger production of pain reducing -endorphin
Narcotic like pain reduction --- enkephalin release
Pituitary gland??? Most likely hypothalamus --- blood brain barrier issue

52. Low Frequency TENS
Actual relief may take some time following treatment
Lasts longer than high ƒ TENS
Uses:
Chronic pain
Pain due to damage to deep tissues
Myofascial pain
Pain caused by muscle spasm

53. Brief – Intense TENS Noxious level, motor level High pulse frequency
Greater than 100 pps
Long pulse duration
300 – 1000  sec
Treatments lasting a few seconds to a few minutes

54. Brief – Intense TENS
Pain relief through activating mechanisms in the brain stem
Dampen or amplify pain impulses
Feedback loop
High level of analgesia
Effects tend to be transitory
Recommended for pre-exercise
Endogenous opiate central biasing theory

55. IFC Interferential current 2 ACs on 2 channels
1 channel produces constant high frequency sine wave
4000 – 5000 Hz
Other channel produces a sine wave of variable frequency
X pattern
Premodualtion – 2 pad setup; interference current generated in machine

56. IFC Two independent channels combine to form an interference wave
Frequency of 1 – 100 Hz
Constructive interference
2 waves in perfect phase collide and form one single larger wave
Destructive interference
2 waves perfectly out of phase, cancel each other out, producing no wave

57. IFC
IFC combines constructive and destructive interference patterns to form a continuous interference pattern
Occurs when 2 circuits have slightly different frequency (+ 1 Hz)
Resultant waveform drifts between constructive and destructive interference patterns

58. IFC Rate of change is known as beat pattern
Difference in frequency between the 2 circuits
Beat produced elicits responses similar to TENS, but is capable of delivering a greater total current to the tissues (70 –100 mA)
Beat pattern = difference between the 2 circuits

59. IFC Low skin resistance
Inside tissues, interference between 2 waves reduces the frequency to a level that has biological effects on tissue
Low skin resistance – inverse relationship to frequency
4000 Hz = 40 Ohms

60. IFC and Pain Control High beat frequency Sensory level stimulation
100 Hz
Sensory level stimulation
Gate theory
Low beat frequency
2 – 10 Hz
Motor level stimulation
Opiate release

61. IFC and Neuromuscular Stimulation
Medium beat frequency
15 Hz
Muscle pump
Increased venous and lymphatic return
Edema reduction

62. IFC and Time Modulated AC
AKA Russian wave
Theory – 2500 Hz carrier sine wave, burst modulation
Dr. Yakov Kots
30 – 40% increase in strength compared to isometric training alone
Increased muscular endurance
Changes in velocity of contraction
These results have never been replicated in USA
Isokinetic principles related to velocity change
Rocky III or IV??

63. High Voltage Pulsed Stimulation
Monophasic current
Twin-peaked waveform or Train of 2 single pulses
phase duration of 5 to 260 sec
Average current does not exceed 1.5 mA
Pulse charge less than 4 microcoulombs
Voltage > 150 V needed to stimulate motor and sensory nerves
Electrode placement in general terms
Monopolar: focus of treatment is over a wide area
Sensory level pain control
Edema reduction
Point stimulation

64. Uses
Muscle reeducation
Nerve stimulation
Edema reduction
Pain control

65. Muscle Reeducation Intensity Strong, comfortable contraction
Pulse Frequency
Low (<15 pps) individual contraction
Moderate (35 – 50 pps) tonic contraction
Polarity
+ or –
Electrode placement
Bipolar: proximal & distal to muscle
Monopolar: motor point
Most useful purpose
Re-teach muscle to contract

66. Pain Control: Gate Theory
Intensity
Sensory level
Pulse frequency
60 – 100 pps
Phase duration
< 100sec
Mode
Continuous
Electrode placement
Directly over painful site
(+) Polarity for acute pain
Repels acid reaction
(-) Polarity for chronic pain
Vasodilation properties

67. Pain Control: Opiate Release Mechanism
Intensity
Motor level
Pulse Rate
2 – 4 pps
Phase duration
150 – 250 sec
Mode
Continuous
Electrode Placement
Over painful site, trigger point, acupuncture point, or distal to the spinal nerve root

68. Pain Control: Brief-Intense Protocol
Intensity
Noxious
Pulse rate
> 120 pps
Phase duration
300 – 1000 sec
Mode
Probe (15-60 s at each site)
Probe placement
Gridding technique

69. Edema Control: Sensory Level
Intensity
Sensory level
Pulse duration
Max duration allowed
Pulse frequency
120 pps
Polarity
– electrode over injured tissue
Mode
Continuous
Electrode placement
Immersion, grouped
Treatment duration
4 – 30 min treatments, 60 min rest
Low pps does not affect edema
1 treatment a day will not reduce edema
Pain relief – long term
Start within 6 hours to increase effectiveness of treatments

70. Edema Control: Motor Level
Intensity
Strong, comfortable contraction
Pulse frequency
Low
Polarity
+ or –
Mode
Alternating
Electrode placement
Bipolar: ends of muscle
Monopolar: course of venous return system
Milking
Elevate limb

71. MENS Microcurrent Electrical Nerve Stimulation Subsensory level
1/1000 amperage of TENS
Pulse duration 2500 x TENS
Does not excite peripheral nerves
DC, AC, or pulsed
Use is not substantiated in professional literature
Anecdotal and sport personnel testimonials

72. MENS Does it work? Theory:
Currents below 500 A increase the level of ATP
Increased ATP production encourages amino acid transport and increased protein synthesis
Tissue trauma affects electrical potential of injured cells
Creates greater resistance to flow

73. MENS Theory continued
Body’s bioelectric current follow path of least resistance
Not through injured tissue
MENS introduces current flow through injured site increasing ATP production
Studies have shown that subthreshold electrical stimulation has a effect on cell membrane properties, neurological responses and ionic responses
Used implanted electrodes
Skin resistance?
DC would seem to benefit more, but does not overcome skin resistance at low amperage
AC pulsed is used
Therefore, providing metabolic energy for healing

74. Neuromuscular Electrical Stimulation
Muscle reeducation
Spasticity reduction
Atrophy delay
Strengthening
Recruitment order reversed
Isometric
Stimulates (recruits) type II motor fibers 1st, produces much stronger contraction
Large amp, long pulse duration
Stronger stimulation than other forms of electrical stim

75. NMES Peak amperage To tolerance Pulse duration 50 – 300 sec
Pulse frequency
1 – 200 pps
Pulse charge
< 10 mQ

76. Iontophoresis
Introduction of medication ions into skin using low-voltage, high amperage DC
0 – 5 mA
Skin impedance
500 ohms – 100 kohms
Primary path of current/medication flow is through hair follicles and skin pores

77. Iontophoresis
Applied current must be sufficient to overcome skin resistance
Once medication is in tissue, it spreads via passive diffusion
Electric current no longer plays role
Medication tends to remain highly concentrated within tissues directly below introduction site
Rate of diffusion is low

78. Iontophoresis Electrode setup is monopolar
Electrode with medication is active electrode
Biophysical effect obtained is dependent on the medication used
Typical use is to decrease inflammation
Dexamethasone
Dosage delivery based on relationship between amperage of current and treatment duration
Current amperage (milliamps) x treatment time = mA/min
5mA x 10 in = 50mA/min

79. Iontophoresis Warning
Burns or severe skin irritation may result due to application of DC
Related to hydrogen and hydroxide ions generated by current