An exoskeleton, in contrast to an endoskeleton, is an external anatomical feature that supports and protects an animal’s body. All arthropods (such as insects, spiders and crustaceans) and many other invertebrate animals (such as shelled mollusks) have exoskeletons. Lobsters, for example, have tough outer shell systems which provide rigidity and shape to their bodies.
An insect’s exoskeleton (integument) serves not only as a protective covering over the body, but also as a surface for muscle attachment, a water-tight barrier against desiccation, and a sensory interface with the environment. It is a multi-layered structure with four functional regions: epicuticle, procuticle, epidermis, and basement membrane.
Humans have long used armour as an artificial exoskeleton for protection, especially in combat. Exoskeletal machines are also used for medical and industrial purposes. Powered human exoskeletons are a feature of science fiction writing. Orthoses are a form of exoskeleton.
So when Kanga said our players are skinners, he meant they use their solid skin to maintain their shape, and that makes steroids useless.