Thanks for the links, mrsD. I would agree with the Wikipedia article that the trolamine salicylate probably does penetrate into the underlying muscle tissue.

When I first started getting the pulsing sensations in my legs, I didn’t initially think to use Aspercreme as I had thought of it only as a minor pain medication. When the pulsing began keeping me awake at nights, however, I decided to try it and got a pleasant surprise. By the way, I use the cream not the lotion, and so far its been working well for me.