I'm sorry that you've not had any replies to your question so far, and although I've never had one myself, I do believe it's rather a simple procedure. (I was a nurse)

It's usually done with local anesthetic for the needle biopsy. The open biopsy is done under local anesthetic plus sedation, so although you're awake... you should be a bit groggy.

I found this information on PubMed and it explains things fairly well:

"There are two types of muscle biopsy:

A needle biopsy involves inserting a needle into the muscle. When the needle is removed, a small piece of tissue remains in the needle. The tissue is sent to a laboratory for examination. More than one needle stick may be needed to get a large enough sample.

An open biopsy involves making a small cut in the skin and into the muscle. The muscle tissue is then removed." http://www.nlm.nih.gov/medlineplus/e...cle/003924.htm

That site gives lots of information about how it's done, why it's done and what to expect.

It also goes through the diagnoses that this test is used for.

I hope that helps a bit.