Part one — mechanism
Before any program, the physiology: proprioception, motor control and joint stability in bodies whose tissue behaves differently.
Ligament and capsule provide passive restraint at the end of range — cheap, automatic, always on. Where that restraint arrives late, muscle has to supply position actively instead. Nothing looks wrong from outside; it simply costs energy continuously, which is why standing in a queue can be more tiring than a workout.
Mechanoreceptors sit inside ligament and capsule. More compliant tissue reports later and less sharply, so the internal map of where a limb is becomes approximate. The brain compensates with vision and with extra effort, which is why performance drops in the dark, on uneven ground, or when tired.
Controlling the last fifteen degrees of a range is learned separately from being strong in the middle of it. This is the single most under-prescribed thing in this population, and the reason 'you're flexible, just stretch' so reliably makes things worse.
Compliance is not confined to joints. Venous walls hold more blood below the heart on standing, so the upright reflex has less to work with — which is why movement planning and orthostatic tolerance are one conversation, not two.
Applied to compliant tissue
Mechanisms behind this page
Next: how to move them →