The Root Variable: The Constant Reference Force Every element of this protocol is an elaboration of a single fact, and the protocol cannot be understood until that fact is stated plainly. The human body did not evolve under gravity merely as a load it must resist. It evolved under gravity as a constant reference signal. One g is the force against which the body continuously calibrates effort, posture, fluid distribution, bone remodeling, muscular tone, and the daily cycle of exertion and recovery. Effort against gravity is the proprioceptive proof that work has occurred. Rest is the recovery from that accumulated, gravity-referenced load. The diurnal cycle of work and sleep is anchored, at the somatic level, by a force the body is always working against and always measuring itself by. Remove that force and the body does not simply lose a load. It loses its reference. A system that has lost its reference signal does not know when it has done enough. It does not know when effort has occurred, because nothing resisted the effort. It does not know when rest is earned, because no load accumulated to recover from. The body in microgravity does not know when to rest, and it does not have a biological reason to. This is the root variable. Every documented degradation of long-duration spaceflight — musculoskeletal, cardiovascular, neuro-ocular, circadian, immunological, and behavioral — is a downstream expression of the body operating without the constant reference force it evolved to require. The preservation paradigm's deepest error follows directly. The constant reference force was never the stressor. It was the signal. One g does not damage the body in space. The absence of one g does. The countermeasure is therefore not to protect the crew from the environment but to restore the reference force the body lost. The continuous mechanical loading garment described in the crew Parts is the mechanism by which the reference force is restored, and because the reference force is the root variable, that garment is simultaneously the musculoskeletal, the cardiovascular, and the behavioral master countermeasure.
Douglas Webb (Sun,) studied this question.