Abstract Human physiology is commonly interpreted through biochemical, neurological, and localized structural models. While these frameworks are essential, they often underrepresent a fundamental physical constant shared by all terrestrial organisms: continuous life under gravity. This paper proposes an additional organizing principle: skeletal load-bearing efficiency under gravity as a systemic regulatory variable. The Reflexive Axis is introduced as a functional framework describing how mechanical load is transmitted through the body and how this transmission influences muscular recruitment, respiratory mechanics, autonomic regulation, interstitial fluid dynamics, and long-term tissue adaptation. Rather than treating posture as alignment or muscular stabilization as a primary solution, the model suggests that many chronic dysfunctions emerge from a persistent substitution of structural bearing with muscular holding. In this condition, load is insufficiently conducted through the skeletal system and is instead managed through chronic co-contraction, respiratory bracing, and elevated energetic cost. A constraint-based observational probe, centered on the sit-to-stand transition and the distinction between allowing and doing, is proposed as a practical and falsifiable entry point for empirical investigation. The framework does not replace existing medical models, but offers an infrastructural layer through which chronic pain, fatigue, inflammatory persistence, and degenerative patterns may be reconsidered.
Israel Don (2026) studied this question.