Cold therapy can help reduce pain and swelling by which mechanism?

• A. Increases pain by speeding nerve impulses
• B. Increases bleeding at the injury site
• C. Causes vasoconstriction and reduces bleeding or swelling
• D. Has no effect on pain or swelling

Answer: (C)

Cold therapy reduces pain and swelling mainly through vasoconstriction: applying cold narrows the blood vessels in the injured area, which lowers blood flow and limits bleeding into tissues, helping to reduce swelling. The cooler environment also slows tissue metabolism and nerve conduction, which dampens pain signals. So the mechanism is the reduction of bleeding or swelling via vasoconstriction. The other statements contradict how cold affects the body—cold does not increase pain or bleeding, nor does it have no effect—so they don’t fit.