Skills Lab #5 – Electrical Stimulation
Name:
Introduction
The use of electrical stimulation incorporates a wide variety of application techniques. Knowledge of
the fundamentals enables the practitioner to become familiar quickly with the capabilities of any unit and
underscores the fact that a single current type can be manipulated to provide a wide range of effects. One
patient’s perceptions of the relative comfort of a specific parameter may differ dramatically from those of
another patient.
Some protocols call for sensory-level stimulation only, whereas others use an electrically induced
muscle contraction. Occasionally, even a noxious stimulus is desired. Each of these sensations results from
the response of a particular type of nerve. Whether a nerve fires in response to electrical stimulation is
determined by the nerve’s diameter and depth and by the pulse duration and intensity of the stimulation.
The larger diameter of the nerve, the lower its resistance and the lower the amplitude necessary for
its stimulation. Logically, deeper nerves require greater amplitude for stimulation than more superficial
nerves. In normal, innervated tissue, the order in which nerves are stimulated is constant. As the intensity
is increased, sensory fibers are stimulated first, followed by motor nerves and then pain fibers. If the
intensity is increased past the point of pain, muscle fibers are then directly stimulated. Short pulse
durations allow for the greatest selectivity in the stimulation of these fibers. As the pulse duration is
increased, the amount of selectively between the individual fibers is decreased.
An electrical current travels through the body by forming a sequence of circuits, opting for the path
of least resistance. Changing the configuration of the electrode placement alters the path of the current,
although the area of greatest current density remains directly under the electrode(s) with the smallest
surface area. The depth of the treatment effect corresponds to the proximity of the electrodes, with the
depth increasing as the space between the electrodes increases.
When using electrical stimulation to elicit a muscular contraction, the placement of the electrodes
greatly influences the amount of current necessary to elicit a contraction. Placing the electrodes directly
over the motor points produces a maximum motor response using a minimum of current. If the current
density over the muscle or muscle group is kept high, more motor points (and therefore motor units) will
be recruited into the contraction. Increasing the output intensity by stimulating motor nerves in adjacent
areas also has the same effect.
Almost any type of electrotherapy modality can elicit a muscle contraction in normal, healthy
muscle. All that is needed is sufficient intensity to depolarize the motor nerve. Certain forms of electrical
stimulation may depolarize the motor nerve more easily and with greater comfort.
Cold application has been thought to decrease pain by decreasing the excitability of the paincausing nerve. Cold modalities are frequently used for a temporary reduction of pain to enhance the
subsequent treatment. For example, cold might be used before or during potentially painful active rangeof-motion exercises in a technique known as cryokinetics.
Purpose
The purpose of this lab is
1. to introduce students to the various techniques associated with electrical stimulation
2. to become familiar with the various protocols and parameters of electrical stimulation and how
changing the parameters alters the perception of the current.
3. to apply the theory of electrical stimulation in the laboratory setting.
Skills Lab #5 – Electrical Stimulation
Indications
 Acute injuries causing pain or edema
 Muscle re-education after injury
Name:
Contraindications
 Areas of sensitivity (sensory nerve fiber
excitement)
 Cardiac disability – pacemaker, etc.
 Pregnancy
 Over the lumbar spine (crossing spinal
cord)
 Cancerous lesions/tumors
 Sites of infection
 Exposed metal implants
Materials Needed:
1. Electrical stimulation machine (NMES, TENS unit)
2. Various sized electrodes
3. Gulick tape measure
Testing Procedure:
1. Each student will be introduced to the equipment used in this skills lab. This skills lab will be more
demonstrative than prior skills labs.
2. Students will prepare the treatment site by measuring a distance of 3” and 6” on the right & left
forearms.
3. Each student will be connected to the same E-stim unit with electrodes placed on the same
anatomical sites.
a. Students will chart their perception of the current as intensity is adjusted.
b. As each type of nerve is stimulated, students will chart the occurrence on the table provided.
4. Electrode size and placement distance will be changed and the demonstration will be repeated.
a. 2x2” electrodes, 3” apart
b. 2x2” electrodes, 6” apart
c. 2x4” electrodes, 3” apart
d. 2x4” electrodes, 6” apart
e. 1x1” electrodes, 3” apart
f. 1x1” electrodes, 6” apart
Skills Lab #5 – Electrical Stimulation
Name:
Type of stimulation used: _________________________
Intensity Level
0
Electrode
size:
Electrode
distance:
●
○
2x2”
2x2”
2x4”
2x4”
1x1”
1x1”
3”
6”
3”
6”
3”
6”
Sensory Nerves
Motor Nerves
LABELING KEY
□
Pain Nerves
Skills Lab #5 – Electrical Stimulation
Name:
Review Questions
1. How did your perception of the current change as intensity was increased?
2. At what intensity were the sensory nerves first stimulated? Motor nerves? Pain nerves?
3. How did you know that each type of nerve was being stimulated?
4. Which treatment protocol gave the strongest perception of the current?
5. Describe current density and how it was changed in this skills lab.