Final answer:
Clients are instructed to use a TENS unit on the low-frequency setting to stimulate the release of endorphins for pain relief and promote better healing with less risk of discomfort or tissue damage.
Step-by-step explanation:
A client with lower back pain using a transcutaneous electrical nerve stimulator (TENS) unit may be instructed to use it on a low-frequency setting to manage pain effectively. This is because low-frequency settings can stimulate the release of endorphins, which are the body's natural painkillers. High-frequency settings tend to block pain signals at the spinal cord level via the gate control theory but do not provide the longer-lasting pain relief associated with endorphin release.
The low-frequency setting is also believed to improve healing by providing a gentler stimulation that promotes circulation and can be sustained for longer periods without discomfort or the risk of tissue damage. Therefore, the therapeutic use of the low-frequency setting on a TENS unit aligns with the growing body of research that suggests that precise and low-level electrical stimulation can aid in healing and pain management.