Which of the following shows the best conductivity of all tissues to an electrical current?

• A. Skin
• B. Tendon
• C. Bone
• D. Muscle

Answer: (D)

Electrical current travels best through tissues that have high water content and many ions. Muscle tissue is rich in intracellular and extracellular fluids and electrolytes, with many parallel pathways along the fibers, which provides lower resistance and allows current to flow more readily. In contrast, bone is mineralized with little free water or ions, making it a poor conductor; tendon is dense collagen with low water content and few ions, also resisting conduction; skin has a protective outer layer that adds impedance and limits current flow until it reaches deeper tissues. So muscle shows the best conductivity among these options.