I took Exercise Physiology through American Public University as an online class. It was 8 weeks long, 3 credit hours, and I believe was $810 for the tuition. Ohio State, who I was taking the class for, approved me to take it as an online class. The other benefit of American Public is that the classes start monthly , so you have a lot of flexibility to decide when to start.
The class itself was not too hard, especially the first few weeks if you have already taken A&P, most of the beginning work was review of the musculoskeletal system. My professor was Dr. Thomas Walker, and while he was a fairly strict grader, he always responded promptly to any questions and was very involved in the discussion boards.
I can upload the syllabus for the class if you are interested.