If I’ve learned anything in PT school, it is never to be amazed. Some things you think may be so miniscule in terms of their importance actually have a much greater impact on the body than you’d thing, and in this case, I’m talking ice.
I’ve iced before after long runs and hard workouts, but I’ll admit, I never really knew the science behind it too much- just that someone told me it was smart to do.
Well, of course I have to share the knowledge- new knowledge I have about ice (or if you want to be technical, cryotherapy).

I bet you are super jealous that you don’t get to read articles such as this all the time

Actually, the articles I’ve had to read on ice are more interesting than one would initially think. The article above was one of 3, and that one specifically looked at whether or not greater amounts of adipose tissue (fat) caused the need to keep ice on the injury longer- and it did because adipose tissue actually is a poor conductor of heat, so it takes more time for the heat to be absorbed into the ice.
On that note, even though I’ve taken physics, I never thought of icing that way. I always just, “I’m getting colder.” In fact, ice melts because it is absorbing the heat from whatever surface its on- in this case, tissue (or skin). Anywho, what does ice do for you?

What happens when muscle tissue is injured?
There is the primary injury- which could be the initial contact if you sustained an injury from something like a kick in the shin or falling and spraining and ankle. Then there is secondary injury which is the injury to surrounding cells that would be otherwise healthy and uninjured.
This is caused by two mechanisms-
secondary hypoxic injury and
secondary enzymatic injury. Basically, when tissue is injured it has a decreased supply of oxygen-leading to alterations in metabolic pathways to produce energy (hypoxic injury) and the release of enzymes that fight injuries (enzymatic injury).
All of these things lead to cells using an inefficient manner to exist leading ultimately to local cell death.
Ice, in a nutshell, has been shown to
slow these processes in injured tissue. Therefore, cells that may have become injured secondary to an initial injury could be “saved” (haha) from cell death. The less cells you have die after injury- the quicker you recover.
While the articles I looked at looked at ice in acute injury situations, ice is good after intense workouts if anything just because it feels good.
The main takeaway is:
- Ice decreases secondary hypoxic and enzymatic injury to cells
- Ice decreases metabolic demands of hypoxic (cells lacking oxygen) cells- allowing cells to survive longer after injury
- Ice decreases inflammation, pain, and muscle spasm
Also, research has shown that crushed ice (or solid ice) is more affective at reducing muscle temperature than gel packs. The solid ice has to absorb more heat in order to melt, cooling the tissue more than the gel pack that does not change state and does not absorb as much heat.
Hopefully this puts a little science behind why you may use ice after injury. The previous theory that it causes vasoconstriction in the blood vessels and reduces edema is less supported than the points I just brought up. The most current research says the main effect of ice is to decrease metabolic demands due to a decreased temperature.