It's an interesting technical challenge because serums and creams only penetrate so far (not far) into the skin.   A serum or cream would need to traverse the skin, subcutaneous fat and the fibrous layer on top of the muscle to get into where it needs to be ---- the center of the muscle!   Also, how do you insure safety??  What if someone accidently rubs it into their eye?  You can see the difficulty.  It may be a ways off still.  Dr. I