If I'm in pain, which one works best?
The short answer is -- whichever one feels best, is best!
Both heat and ice fall into a category of therapies that don't fix anything, but they can be helpful by making you more comfortable. Neither will speed healing, and there's no danger of accidentally using the "wrong" one, and hurting yourself in some way.
Think of heat and ice as the same kind of therapy as Tylenol. Tylenol doesn't "heal" you, but it can definitely help you get through a rough patch where you're hurting a lot.
If you're having trouble sleeping, for example, and you find that using a hot pack helps you sleep, that's exactly what heat and ice are useful for. Then can help you get through a painful period as you recover, and handle work or daily life with a little more comfort.
With both heat and ice, our goal is that you don't need them forever -- just for a week or so perhaps, when you're hurting the most.
Once you're feeling great again, there's no need to apply either of them.
How heat can help
Heat 'loosens tight things'. Meaning, if you feels stiff, sore or tight, heat can help loosen things up and get you more comfortable.
We've all notice how much a hot shower can make us feel looser and less stiff. This is because muscles are like taffy -- when they're cold, they're stiff and brittle. But when they're warm, they get nice and flexible.
Heat also increases blood flow, which is why you may notice your skin gets a little red when you've been outside in the heat, or after applying a hot pack.
Heat also tends to soothe sore, achy feeling muscles. Heat just feels good!
Heat can be applied all kinds of ways: hot bath, hot shower, hot tub, hot water bottle or heating pad. Any of these can work, and are fine to try.
The effects of heat are temporary, but can give much-needed relief if you're in a lot of pain. As long as you're not burning yourself, it's totally safe to use.
If you feel stiff, tight or achy, try applying some heat for 15 minutes, and see if you feel better. If so, great -- that's what it's for! Use it as it seems helpful.
How ice can help
Ice shrinks swelling and relieves pain.
If you've ever had really cold hands or feet, you may have noticed that they feel a bit numb until they start warming up. This is how ice numbs pain.
Also, if you've ever sprained your ankle and saw it get big and swollen, ice can help shrink that swelling. Doctors often prescribe ice baths or ice wraps after a knee surgery -- both for pain relief, and to keep swelling from getting out of control.
Swelling itself can damage tissue in theory, but it's rare for most people to have that much swelling. A little puffiness around a joint, or a bruised area is typically what we see with most patients. And for a little puffiness, ice can help manage those symptoms well
Ice can be applied with either an ice bath (that you might submerge your foot in, for example), a chemical cold pack (once you "break" it, a reaction occurs in the pack that makes it cold), or just a bag of ice. Any of these are fine to try.
With ice, I recommend having a thin layer of fabric between you and the ice, so the cold isn't applied directly to your skin. It'll still get cold, and protects your skin better that way.
If you have visible swelling or intense pain, try applying cold to the area and see if it feels better. If so, great -- that's what it's for! Use it as it seems helpful.
What if I'm not sure how bad my injury is?
If you're ever unsure about your health status -- especially if you've had a trauma or are developing new or worsening symptoms -- definitely get checked out by a doctor. It may be nothing, but it's absolutely worth it to rule-out any scary conditions that may need medical care right away.
And while both heat and ice are very safe, and can help make you more comfortable during your recovery, do not apply them to open wounds. Your doctor can advise you when & if ice or heat are safe to apply in those cases.
In summary, heat and ice are very useful for managing pain or discomfort, even though they don't "speed healing".
And there's no "wrong" way to apply them -- you can go back and forth between them, to see which one feels best. If one feels better than the other, use that one -- as it seems helpful!