Which statement about thermotherapy’s effect on pain and muscle spasm is correct?

• A. Thermotherapy decreases pain and muscle spasm.
• B. Thermotherapy increases pain and muscle spasm.
• C. Thermotherapy has no effect on pain.
• D. Thermotherapy worsens muscle function.

Answer: (A)

Thermotherapy raises tissue temperature, which helps relieve pain and reduce muscle spasm through several interconnected effects. Warmer tissue causes vasodilation and increased blood flow, aiding delivery of oxygen and nutrients while helping remove waste products that can irritate nociceptors. It also relaxes muscles by decreasing the excitability of muscle spindle fibers, reducing reflexive guarding and contraction. The warmth can also engage cutaneous thermoreceptors that modulate pain signals, contributing to analgesia. Taken together, these changes explain why heat therapy commonly decreases both pain and muscle spasm and can improve movement. The other statements don’t fit because heat does not typically increase pain or spasm, it does have a demonstrable effect on pain, and it does not worsen muscle function; when used appropriately it often enhances function, especially in subacute or chronic conditions.