Human structure and function are mediated by movement. Structure affects movement. Movement, or lack of movement over time, affects structure. The effects can be positive or negative. Deficiencies in any component of physical health — poor body awareness, improper alignment, limited flexibility, or an imbalance of muscular strength—eventually lead to dysfunction, pain, performance decrements or injury. A comprehensive physical health plan requires assessment of musculoskeletal structure and function, or rather, physical competencies. Development of these physical competencies is the key to physical health and athletic performance.