HVGS Flashcards
PHYSICS FUNDAMENTAL
HVGS builds a circuit where human body
(nerves) is part of the circuit
physics fundamentals
‣ Nerves transmit signals to the brain via electrical
pulses
‣ Nerves can be affected by externally applied
electrical current
‣ HVGS creates a circuit that incorporates the
human body
‣ HVGS provides electric current (DC) to nerves
supplying muscles creating a contraction
‣ HVGS uses direct current - low-frequency, shortduration
pulses, and high voltage
PHYSIOLOGICAL EFFECTS
‣ Stimulates muscle activity via selectively depolarising motor nerves to generate a contraction of the muscle fibres ‣ Short duration current allows for stimulation of motor nerves compared to sensory nerves or nociceptors ‣ Other uses include: ‣ Pain relief and swelling management ‣ Uses similar parameters to other EPAs ‣ Wound healing ‣ Stimulates the epidermal stem cells to assist with wound healing
physio aim
Elicit a muscle contraction by stimulating the
motor nerves
CONTRAINDICATIONS
Vicinity of uterus in pregnancy
Over inbuilt stimulator (eg. Pacemaker)
PRECAUTIONS
Circulatory Insufficiency Risk of dissemination Exacerbation of existing conditions Unable to communicate Sensory loss
Settings/Dosage
POLARITY
Negative: selects polarity
of active electrode to go over the motor point
(blue on the old machine and red on the multifunction
TIME: Surge ON/OFF
* depends on exercise
parameters
amp: muscle contraction
PULSE SHAPE
Continuous
Square
Saw Tooth
FREQUENCY
Motor: start at 30-50 Hz increase
* may need to start at 90Hz
TIME: Duration
* depends on exercise parameters
warnings
WARNING
When having electrical stimulation you should feel a strong tingling sensation and a muscle contraction. If
you feel anything more than this or any pain you must
call me immediately otherwise you may risk skin or other tissue damage under the electrodes.
KEY POINTS
‣ Apply dispersive larger electrode proximally and smaller active
electrode over the motor point of the target muscle
‣ Use exercise parameters for DURATION and SURGE ON/OFF
‣ Endurance - longer on time, less rest, more repetitions
‣ Strength- shorter on time, more rest, less repetitions
How are the electrodes usually placed for HVGS
Usually a unipolar application for motor stimulation with
a larger dispersive and a smaller active electrode.
Current density is greater under the active electrodes.
How would you vary the electrode placement if the
patient did not have a nerve supply to the muscle?
Use bipolar application with two electrodes the same
size at each end of the muscle belly
How do you get a contraction in a denervated muscle?
How do you get a contraction in a denervated muscle? Current depolarises the muscle membrane
Where do you position the active electrode for the most
effective muscle stimulation?
Over the motor point.
What is the motor point and how do you find it?
What is the motor point and how do you find it?
Where the nerve enters the muscle and where there are
most motor units. Usually the largest point of the
muscle bulk. May have to find it by trial and error.
Why do you choose negative polarity ?
It makes the active electrode negative. As the resting
membrane potential of the nerve is already negative on
the inside, it facilitates membrane depolarisation.
