Here's a fascinating and creative take on functional structure:
Tensegrity is a term popularized by Buckminster Fuller when he built the first geodesic dome. These buildings transfer loads through tension beams which are connected in triangles. The integrity of this tension system is crucial to the stability of the structure (tension integrity = tensegrity). When a force pulling in one direction is equally opposed by a force pulling in the opposite direction, stability is achieved for that direction only. For complete rigidity of a structure the various lines of force form a series of isosceles triangles. These are called tensegrity structures. Our bodies do not require this amount of rigidity, in fact our function would be limited because of it. However, the linking together of muscles through their connective tissue bonds (fascia, ligaments, and bones) can create momentary tensegrity systems that assist in the transference of force without too much compression through the joints. Exercises, which connect muscles both individually and collectively, provide tensegrity for the direction of load being imposed.
---Lee, BSR, FCMAT, Diane, An Integrated Model of "Joint" Function and Its Functional Assessment, 4th Interdisciplinary World Congress on Low Back & Pelvic Pain, Montreal, 2001.
Proprioceptive Neuro-muscular Facilitation (PNF) tests and treats patterns of movement that utilize all of a joint's movements through all three dimensions. Since most muscles' tendons and their attending structures (fascia, nerves) attach to their nearby joints, taking a joint through its functional patterns that include abduction/adduction, extension/flexion, and internal & external rotation challenges all of the structures' strength, mobility, range of motion and, most importantly, neuro-muscular coordination. The points in the movement that present as weak, ratchety or painful reveal dyscoordination of a system of structures through that particular part of the pattern of movement. This need not show up in testing single muscles in single planes of strength such as is done in kinesiology. And building strength alone will not provide results. The system as a whole must be reeducated in how to behave as a system. PNF provides systemic functional reeducation.