What is the effect of applying heat to muscles?

• A. Causes vasoconstriction
• B. Stops blood flow
• C. Increases inflammation
• D. Relaxes and improves blood flow to muscles due to vasodilation

Answer: (D)

Applying heat to muscles causes vasodilation, which opens up the blood vessels and increases blood flow to the area. The warmth helps soften and relax tight muscle fibers, reducing stiffness and making movement easier. With more blood flow, oxygen and nutrients reach the muscles while waste products are cleared more efficiently, supporting healing and reducing pain from tension. This is in contrast to cold, which causes vasoconstriction, and to the idea that heat stops blood flow or directly increases acute inflammation. In short, heat relaxes the muscle and boosts circulation through vasodilation.