Therapeutic Modalities and Electrotherapy Flashcards

Which parameter determines the frequency of ultrasound and affects depth of penetration?

Answer: Frequency (MHz)

Ultrasound at 1 MHz penetrates deeper (up to 5 cm) and is used for deep tissues, while 3 MHz penetrates more superficially (1–2 cm) due to higher absorption.

What does a 20% duty cycle in pulsed ultrasound indicate?

Answer: Ultrasound is on 20% of the time and off 80% of the time

Duty cycle is the ratio of on-time to total cycle time; a 20% duty cycle means the ultrasound is active for 20% of each pulse cycle, reducing thermal effects.

Which electrical stimulation waveform is most commonly used for muscle strengthening in a normally innervated muscle?

Answer: Russian current (medium-frequency AC)

Russian current (2500 Hz sinusoidal AC delivered in 50 bursts/sec) is widely used for muscle strengthening because it produces strong, comfortable muscle contractions.

What is the primary physiological effect of cryotherapy in the first 24–48 hours post-injury?

Answer: Vasoconstriction, reduced metabolism, and decreased edema formation

Cryotherapy causes vasoconstriction, slows cellular metabolism, and reduces the release of inflammatory mediators, limiting secondary tissue damage in the acute phase.

Iontophoresis uses which principle to drive medication through the skin?

Answer: Direct electrical current repelling similarly charged ions

Iontophoresis uses direct current to drive ionized medication through the skin; like charges repel, so a negatively charged drug is driven from the negative electrode into tissue.

Which modality is contraindicated over a cardiac pacemaker?

Answer: Interferential current (IFC)

Electrical stimulation modalities including interferential current are contraindicated over or near cardiac pacemakers as they can interfere with pacemaker function.