10 Questions
Why does the current produce maximal summation of muscle contraction?
Because the current is fast oscillating and alternating
What is the effect of gradually increasing the number of bursts on the mechanical relaxation cycle of the muscle?
It interrupts the mechanical relaxation cycle
What is the advantage of the higher frequency of the current?
It reduces resistance to the current
What is the purpose of the inter-burst interval in the current?
To allow tolerance of greater current intensity
Why are the nerves stimulated despite being a medium frequency current?
Because it is interrupted to give a low frequency stimulation
What is the effect of using currents of high intensities?
It produces maximum tolerable muscle contraction
How are the currents typically applied in clinical settings?
Using electrodes applied over the muscle belly
What is the clinical application of these currents?
To stimulate muscle contraction
What is the effect of the inter-burst interval on muscle contraction?
It allows for greater muscle contraction
What is the benefit of using high-intensity currents in bursts?
It achieves muscle hypertrophy
Study Notes
Interferential Current (IFC)
- The resistance of the skin is inversely proportional to the frequency of the stimulating current, resulting in less discomfort at higher frequencies.
- Skin impedance at 50 Hz is approximately 3200 ohms, reducing to approximately 40 ohms at 4000 Hz.
- IFC application at 4000 Hz reduces the stimulation of cutaneous sensory nerves near the electrodes while promoting the effect on deep tissues.
Physiological and Therapeutic Effects of IFC
- The current flowing between each pair of electrodes is insufficient to stimulate nerve and muscle directly until amplitude is modulated by interference.
- IFC reduces the stimulation of cutaneous sensory nerves near the electrodes while promoting the effect on deep tissues.
- Physiological effects depend on factors such as magnitude of the current, mode, frequency, electrode placement, and pathological condition.
- Common effects produced include pain relief.
Types of Electrodes
- Metal plate and pads: used with water-soaked sponges.
- Carbon rubber electrodes: used with conducting gel.
- Suction cup electrodes: provide rhythmic negative pressure, causing mild massaging effect on the skin, stimulating cutaneous sensory nerves and causing slight vasodilatation.
Treatment Parameters
- Intensity: dependent on the desired physiological effect and the tissue to be stimulated.
- Frequency: excitable tissues can be stimulated by low frequency alternating currents.
- Treatment duration: varies widely according to the usual clinical parameters of conditions (acute/chronic) and the type of physiological effect desired.
Russian Current (RC)
- RC is a Medium-frequency polyphasic AC, with a carrier frequency of 2,500 Hz.
- The current is interrupted and delivered in short bursts (burst modulation) with 50 bursts per second, 10 msec burst duration, and 10 msec interburst interval.
- The waveform has a therapeutic frequency of 50 Hz and 400 μsec cycles duration, well suited for activating skeletal muscle.
Advantages of Russian Current
- Fast oscillating alternating current maximally summates muscle contraction.
- Higher frequency reduces the resistance to the current, making it comfortable.
- Interburst interval allows tolerance of greater current intensity.
- Although it is medium frequency, the nerves are stimulated because it is interrupted to give a low frequency stimulation of 50 Hz.
- It can achieve muscle hypertrophy by using currents of high intensities producing maximum tolerable muscle contraction.
Learn about the relationship between the frequency of electrical stimulation and the resistance of the skin, and how it affects the passage of current. Discover how skin impedance changes at different frequencies and its implications.
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