Duty cycle refers to:

• A. The ratio of on time to off time.
• B. The frequency of the current.
• C. The peak amplitude of the current.
• D. The duration of the treatment session.

Answer: (A)

Duty cycle describes how much of each treatment cycle the current is actually on versus off. It’s the ratio of on-time to the total cycle time (on plus off), usually expressed as a percentage. For example, if the current is on for 2 seconds and off for 3 seconds in a repeating cycle, the duty cycle is 2 out of 5 seconds, or 40%. A higher duty cycle means more energy delivered per cycle and greater potential for tissue response and fatigue; a lower duty cycle reduces energy delivery and allows more recovery. This is different from frequency, which is how many cycles occur per second, and from peak amplitude (intensity) or the total session duration.