1. figure out your muscle shapes from references

2. Cut out shapes from an old Garage sale pool float mat.  

You can use big scissors or a jigsaw (be very careful with the jigsaw!!!).

3.Glue the Muscles to an old long sleeve shirt using

Headliner Spray Adhesive from your local auto parts store.

4. Cover with liquid latex Rubber or a 4-way stretch nylon material.