Why do extreme temperatures (hot and cold) make sore muscles feel better?
In: Biology
Source: US DO student
Cold numbs pain. When cold the blood vessels in muscles constrict to preserve heat. With less blood flow, the hormones that signal pain take longer to travel and break down before being as effective. Whenever muscles are hurt they release chemicals into the blood that encourage more blood flow to the area to help recover which also increases the pain signal. These chemicals, like milk, have an expiration after which they no longer work. This is because recovery should only take place temporarily as it uses a lot of the body’s limited blood supply
Once the pain is bearable heat applied briefly (20 minutes) allows more blood to flow as the quick application of heat allows blood to flow more smoothly and quickly, allows the enzymes in cells to work more quickly which includes hemoglobin releasing oxygen more readily
Heat when applied for very long periods may end up heating up the entire body, which results in more blood going to the skin across the entire body in an effort to release excess heat by conduction. A larger portion of Blood is normally stored deeper in the body away from the skin, like hiding under a blanket. Or another way, it’s like holding an ice cube in your fist versus touching with one finger. More blood closer to the skin allows more of it exposed to room temperature.
This would limit blood supply to the injured region, though more serious problems such as burns are more likely especially if using heat that’s significantly higher than body temperature such as boiling water in a bag. Also the body region will also sweat and when trapped under a pack for a long period will promote bacterial growth.
Edit: Grammar
Edit2: Thoughts about heat pack duration added
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