Lot of kids love word searches. By providing students with word searches that use the names of the major muscles and muscle groups, you give them a chance to see those names in print. When they do, the students will become more familiar with the names of the muscles and be more likely to remember them later on.
Pair up students and have one trace an outline of the others' body onto a large sheet of paper. Then ask the students to work together and draw each of the major muscles in the body. After the students have done this, have them label the muscles. Doing this will help the students make the connection between what they are learning about the human body and their own bodies. The finished drawings can be displayed in the classroom to further help reinforce the lesson.
Many students are able to learn difficult concepts and words through songs. Adapt the song "Dry Bones" to use muscle names instead of bones. Teach the class the song. When the students sing the song, have them touch each muscle as they name it. Learning the song will help the students remember the names of the muscles and pointing to the muscles on their own bodies will help them not only remember where the muscle is but also give them a personal connection to the lesson.
Have the students look through magazines and newspapers and cut out pictures of both voluntary and involuntary muscles. When they are finished cutting out the pictures, have them make collages out of the the cuttings, putting the voluntary muscles together into one group and the involuntary muscles into another. Ask them to them label each group. To extend the project, have the students label what the individual muscles are in the two groups they made.