Final answer:
The best site for TENS unit application, particularly for a thin person, is often the lower back because it usually has sufficient muscle mass for effective conductivity. Alternative areas like the upper arm, abdomen, or thigh may be less suitable due to varying muscle and fat distribution that can affect the TENS unit's performance.
Step-by-step explanation:
When determining the best site for TENS unit application, especially in a person who is thin, it's important to consider both the location of the pain and the underlying muscle mass. This is because the TENS unit's effectiveness can be affected by the amount of subcutaneous tissue present, which can influence the conductivity of the electrical currents to the underlying nerves and muscles.
The lower back is often a good location for placing TENS electrodes because it typically has an adequate amount of muscle mass to conduct the TENS unit's electrical stimuli efficiently, even in individuals with a lean physique. The upper arm or abdomen might not be the best choices due to less muscle mass and more variability in fat distribution, which can impact the effectiveness of the TENS unit. The thigh could be a suitable alternative depending on the individual's build and where the pain is located.