Why do extreme temperatures (hot and cold) make sore muscles feel better?
In: Biology
Pain is a signal from your nerves. The signal travels on small fibres.
When you put hot or cold on your body other nerves feel this sensation, but send it over big fibres.
Both meet up at the spine but the signals that come in on the big fibres are given priority.
This is called gate control theory is why both hot and cold work.
Other things are also happening. Cold constricts blood vessels, reducing swelling. If swelling is what is causing the pain, there will be less pain. Cold also slows down how fast nerves can send signals. Fewer signals = less pain.
Heat lets more blood enter the area. This brings nutrients. Sometimes pain is caused because muscles or structures aren’t getting enough nutrients so they ‘cramp’ up. The extra blood lets them relax, which can reduce pain.
Can anyone tell when to do hot and when to apply cold temp?
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When you work out or do anaerobic physical activity, your muscles produce lactic acid. Getting in an ice bath constricts your blood vessels and muscles which helps to squeeze the acid out. Heat dilates the blood vessels helping to improve circulation to get it out and oxygen in. It advances the recovery process.
The immediate relief comes from what others are saying. It serves as additional stimuli to the nerves which covers up some of the pain.
When you workout, for example, your muscles produce a lot lactic acid as a product of burning sugars to release energy. That’s why sometimes you can feel the pain flowing to nearby parts of your body. This is when you want to use cold water, because this will improve circulation and help to remove the latic acid from the muscle. After that you want to use hot water, because it will help you muscle to relax. Relaxing helps it to not be so tense and not hurting all the time. The way is more or less like that: hurt? Yes. Go cold. Then go hot.
As someone with chronic sciatica, the following works well. After work or exercising with pain ice packs are good, if no pain is there then heat packs are the go to promote blood flow and healing.
Hot / cold therapy:
Cold water makes blood rush away from the area
Hot water makes blood rush to the area
Using hot/cold therapy increases circulation to the injured area speeding up the healing process.
Your blood vessels constrict (& this reduce blood flow) when cold & dilate (& this increase blood flow) when warm. Reduced blood flow tends to reduce swelling (useful shortly after an injury or using muscles). Increased blood flow tends to improve healing (useful once the swelling decreases).
I’ll try my best for an ELI5: ~~when we do exercise the muscles in our bodies do loads of little burps as they work. These burps can build up and cause our muscles to feel sore. Some people like to get into really really cold water because this can help! When we get in the cold water our brain worries a little bit about how cold it is and so it pulls the blood from our muscles to help keep us warm. But this also pulls the burps out too! Then when we get out of the water the blood goes back to our muscles but without those burps stinking up the joint! Instead the burps have been replaced with good things our muscles need to heal!~~
(Edit: I know it’s not gases but kids like burps, hell I’m 37 and I like burps hahaha)
Edit 2: thanks for all the love all and to the kind bestower of gold! My very first ever
**Edit 3:** well sorry folks looks like I’ve been spreading misinformation! I’d always thought that lactic acid build-up was one of the causes of pain in muscles post exercise when it isn’t. Seeing as this post was created around a false premise I’ll strike it. Many thanks to u/brerchicken for the heads up!
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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