Evidence from space physiology and habitat engineering studies indicates that sustained exposure to microgravity leads to severe multi-system deconditioning, supporting the requirement for artificial gravity thresholds to maintain astronaut health on long-duration missions.
The retrieved literature consistently emphasizes the physiological toll of microgravity and reduced gravity environments on human health (musculoskeletal, cardiovascular, immune, and metabolic systems). Papers such as [8] and [9] explicitly discuss the necessity of artificial gravity or the insufficiency of partial gravity to prevent progressive deterioration, directly supporting the claim that a minimum threshold of artificial gravity is needed for long-duration space travel. There are no papers refuting this requirement.