After sifting through about fifty zillion articles online and in my filing cabinet, I found an old article a naturopath gave me on the efficacy of hot and cold hydrotherapy, and it seemed to indicate that lukewarm/cold is better than hot/cold if the injury is particularly inflamed. The amount of heat versus cold varies, but there is almost always more heat used than cold. So I was thinking if the injury is particularly cold (as in, cold to the touch, as my joints often get when I have an injury) then hot/lukewarm might be indicated (the "cooling" part would be the air, or removing heat). I guess this would vary based on the individual. Like, maybe if someone is cold all the time even though they live in the desert, you could use hot followed by lukewarm or something.
The theory behind alternating hot and cold is to use heat (or moist heat) to increase the vascular size and transport cellular waste and remove damaged cells, but then use the cold to stop the swelling. I would think that too much inflammation caused by heat would either hurt or be obviously swollen (visually) afterwards and that would be an indication, so I'm guessing that me using heat that doesn't increase swelling even without icing is unlikely to be harmful (someone correct me if you think I'm wrong.)
This gets even more complicated if you talk to homeopaths, who would use fairly mild heat to treat inflammation (and even burns, for that matter.)
Since ice (or heat) is a temporary measure there are absolutely no follow-up studies on this, so even though it's not definitive proof I think people's clinical experience over a long period of time is the only thing to go on for now. Of course if people are just trying to make something hurt less or heal faster then it's not important anyway--I may be one of the few people who wants to see the result of long-term studies of ice.
On the pro-heat front, I found a study that showed that continuous low-level heat wrap therapy is effective for treating wrist pain and one for heat during back pain. These studies didn't compare heat and ice. The ones that do seem to be pretty pro-ice, as much as I want them not to be.
For back pain:
It just says heat and exercise is better than heat or exercise alone, and that just one of the two is better than nothing.
I also found this little disclaimer, which seems to indicate there may be a conflict of interest here as it was funded by Procter & Gamble, who make more money off of their ThermaCare Heat Wrap than they would off of ice packs.
I love science.
FDA device/drug status: approved for this indication (ThermaCare Heat Wrap, The Procter & Gamble Co).
Support in whole or in part was received from The Procter & Gamble Company. Author GNE acknowledges a financial relationship (employee of The Procter & Gamble Co.), which may indirectly relate to the subject of this manuscript."
The wrist pain article covered carpal tunnel, tendinosis, osteoarthritis, strains and sprains. Heat helps with pain relief and grip strength. It scores the same as placebo for joint stiffness and "patient rated wrist evaluation", whatever that is.
So there you have it!