Things You'll Need
Stretch bodysuit with a back zipper
Thin upholstery foam
Thick upholstery foam
Contact adhesive glue
Paintbrush or roller
1 gallon liquid latex
Muscle costumes or muscle suits are usually stretchy bodysuits with sculpted foam muscles on the torso, arms and legs. This type of costume is often used to create a larger-than-life effect for superhuman or creature characters and can be worn underneath clothing as well as painted to resemble exposed textured skin. You can make your own muscle suit sized to your body shape for any style of costume, from fantasy heroes to alien invaders.
Make a Body Double
Put on a pair of trousers and a long-sleeved shirt that you do not mind ruining. Have a friend help you cover the trousers and shirt with duct tape, layering the tape around your body so that it fits fairly snugly.
Have your friend cut you out of the clothes, down the center back of the shirt and trousers. Remove the duct-taped clothes.
Tape the center back of the clothes together again. Stuff the clothes with cotton batting to create a body double.
Run PVC pipes through the arms, legs and torso of the body double so that it can hold the shape of your body well.
Lay the body double onto a large table. Put the stretch bodysuit onto the body double.
Create the Muscles
Adjust the bodysuit so that it is stretched fully over the body double. Safety-pin the sleeve hems, neckline and leg hems to the body double so that the bodysuit does not move around while you are working.
Make a paper pattern for each muscle you want to add to the suit. If necessary, use anatomical reference pictures, such as those linked in the Resources section.
Cut out the paper patterns and lay them over the upholstery foam. Choose thick foam for the larger muscles and thinner foam for smaller muscles. Cut the muscles from the foam.
Glue the muscles to the bodysuit as desired, leaving the back zipper completely free of foam.
Glue pieces of very thin foam between the gaps in the muscles, leaving only the joint areas free.
Finish the Muscle Suit
Add small pieces of foam to the muscle areas to add definition as desired and finish shaping the other muscle pieces.
Open a container of liquid latex. Dip a paintbrush into the latex and begin applying latex onto the foam muscles with your choice of applicator. You can use a paintbrush, roller or even a sponge.
Continue applying a layer of liquid latex all over the front of the bodysuit. Let the latex dry, then apply a second layer. You can stipple this layer if you would like your suit to have a scaly skin texture.
Let the latex dry, then turn the body double over. Coat the back of the suit in two layers of liquid latex, leaving the zipper alone. Let the latex dry.
Paint the entire muscle suit with latex paint, using an airbrushing machine. Let the paint dry, then remove the suit from the body double.