Andrew Biel

Like Billy J., author Andrew Biel was a skinny kid convinced he had no muscles—until he accidentally discovered one under his armpit! Over the years, he learned more about muscles, wrote the best-selling textbook Trail Guide to the Body, and now uses his muscles to kayak, cross-country ski, and hike.

Robin Dorn is a painter and scientific illustrator specializing in human anatomy. She enjoys keeping in touch with her whimsical side in the company of such characters as Ms. Muscles.