Artificial Gravity as a Bone Loss Countermeasure in Simulated Weightlessness

Abstract

The impact of microgravity on the human body is a significant concern for space travelers. We report here initial results from a pilot study designed to explore the utility of artificial gravity (AG) as a countermeasure to the effects of microgravity, specifically to bone loss. After an initial phase of adaptation and testing, 8 male subjects underwent 21 days of 6° head‐down bed rest to simulate the deconditioning associated with space flight. Six of the subjects underwent 1 h of centrifugation (AG, 1 gz at the heart, 2.5 gz at the feet) each day for 21 days, while 2 of the subjects served as untreated controls (CN). Blood and urine were collected before, during, and after bed rest for bone marker determinations. Comparing the last week of bed rest to before bed rest, urinary excretion of the bone resorption marker n‐telopeptide increased 95 ± 59% (mean ± SD) in CN but only 32 ± 26% in the AG group. Similar results were found for another resorption marker, helical peptide (increased 57 ± 0% and 35 ± 13% in CN and AG respectively). Bone‐specific alkaline phosphatase did not change during bed rest. The study will continue with additional subjects and measures, including calcium tracer kinetic studies. These initial data demonstrate the potential effectiveness of short‐radius, intermittent AG as a countermeasure to the bone deconditioning that occurs during bed rest. Supported by the NASA AG‐Bed Rest Project (IMAG Pilot Study, PIs: WH Paloski and LR Young).