We get a lot of questions in the clinic about ice vs heat when it comes to injuries. Most people have heard that they should use one or the other, but aren’t sure which is best for what injury, when it should be applied, for how long, and most importantly, what the heck does it do anyway?!
When we injure ourselves, whether through chronic repetitive strain or through an accident, our body jumps into protective mode. Blood, rich in reparative cells, rushes to the site of injury and pools. This delivers nutrients to repair tissues, clots the wound if it’s open, and acts as a kind of natural splint to reduce range of motion. A classic example is jamming a finger from catching a ball. Pain alerts the body to the injury (not your loud cursing!) and within minutes, the finger joint has swollen. If you try to bend your finger, you will realize that you can’t move it in the same way because the area is so full of fluids. This response mechanism is actually a good thing, even though it may be a minor annoyance. Your body doesn’t like pain, so it protects the injured area to reduce the chance of further injury
On the other side of things, what happens when we want to get rid of that inflammatory response? We can’t just let swelling and pooled fluid hang around forever because that impaired range of motion can start causing problems for other tissues. Compensatory motions happen as a result of the lost range, and secondary injuries can develop. How can we counteract that oh-so-nice body response to injury? Well, the first step is to get rid of the pooled fluid. In doing this, we flush the tissue and help bring range of motion back. Constricting the vessels that carried that fluid to the injury can be achieved by using ice and compressive force. Most people don’t like that almost painfully cold temperature change that ice brings on when we put it on our skin. Well, our tissues don’t like it much either! When ice is applied, tissues and vessels shrink in diameter, flushing fluid away and disallowing further flow to the injury. If we also add compressive force, say, in the form of a tensor bandage or compression garment, we further shrink the tissues to push fluid away and work against gravity. This is why patients will commonly be prescribed the use of a cryo cuff cold therapy unit after surgery: the compressive wrap and flow of ice cold water around the surgical area won’t allow pooling of blood for an excessive amount of time. A person who has had a knee replacement or ligament tear has to start to move the leg again sometime, so a cryo cuff can help counteract the effects of the inflammatory response.
Sure, cold has its benefits, but what about heat? Generally viewed as the more relaxing temperature therapy, heat does just that: relax and dilate. Applying heat to tissue will increase the size of blood vessels and encourage more blood to flow. It can also help to loosen up the tight, protective muscles around an injury site. However, its best to know when and where go apply heat. Sure, heating an area of injury or pain might feel pleasant, but it can actually have the opposite effect that we want. We likely don’t want to create more swelling and splinting. Therefore, a combination of heat and ice, applied at certain spots, can be more beneficial.
Keep in mind the splinting effect of swelling we spoke about earlier. It’s not just the injured spot that becomes tight and restrictive. Muscles and tendons surrounding the area try to restrict range of motion as well. You might notice that if you strain a calf or hamstring during a run, that your gait starts to change as a result of pain. These compensatory motions use our muscles in different ways than they are used to, creating a whole new section of trigger points and knots. Heating these surrounding muscles before activity or when they feel tight is a good way to increase blood flow to, in turn, increase flexibility so the muscles don’t pull excessively around the injury. This is something therapists will often advise to their clients who are still able to exercise at some level during strain. After the exercise is over, there will likely be a return of swelling in the tissues. Icing the sore spots is a way to counteract that, for the reasons detailed above
A general rule of thumb: ice the sore spot, heat around the sore spot.