Believe it or not, but that is actually a known and mentioned effect. Probably due to increasing blood circulation.
"It’s supposed to get soreness out, but never used it for exercising."
My wife has, for our entire 51 years of marriage, suffered from muscle cramps. Muscles will just decide to "twang up" and get as tight as a guitar string. I can give her relief by massaging, but since beginning WBV, her problems are DRASTICALLY reduced.
I may check it out. Not a lot of people use it. Someone told me they do calf raises on it and it works well.