The book provides fundamental new insights into the structure and function of the healthy neuromuscular system. Recent findings suggest that the musculoskeletal system that supports movement control on Earth is governed by unique principles of structural, biochemical, and molecular characteristics. Mechanical loading by working against normal gravity helps to support principal structures in bone, muscle, and associated subcellular scaffold components. Disuse or immobilization of the body, whether through bed rest on Earth or in microgravity in space, results in considerable loss of bone, muscle, and force, along with downregulation of neuromuscular activity, leading to impaired performance control. The goal is to develop exercise prescriptions to maintain postural control in normal life, aging, and rehabilitation on Earth, as well as for adequate human performance management in space.