I could be completely wrong but it looks like the modern equivalent of a bag of frozen peas treatment that I was recommended many years ago for the early onset of 'tennis elbow'.
That was my immediate guess from looking at the pictures. It looks like a spray chemical of some sort, possibly similar to "Spray Freeze" used in electronics. Spraying it directly on the skin would be a good way to get frost bite, but spraying a dry (or probably better, wet) towel could work well.
"Spraying it directly on the skin would be a good way to get frost bite"
Not necessarily so. Years ago my doctor sprayed ethyl chloride to freeze / numb part of my foot before performing minor surgery. Some discomfort, no pain and definitely no frostbite. Ethyl chloride spray is known to relieve muscle pain as well.