Artificial gravity protects bone and prevents bone marrow adipose tissue accumulation in humans during 60 d of bed rest

Inactivity has been associated with increased bone marrow adipose tissue (BMAT) and bone loss. Artificial gravity (AG) may prevent these complications. This randomized controlled trial investigated the effectiveness of AG at 2 g at the feet to prevent lumbar vertebral BMAT accumulation and bone loss. Twenty-four participants (16 male, 8 female) were bedridden for 60 d at 6° head down tilt. They were randomly assigned to bedrest only (n = 8), continuous supine centrifugation (cAG; 30 min/d), or intermittent supine centrifugation (iAG; 6 bouts of 5 min/d). Serial 3T magnetic resonance (MR) measured BMAT while DXA measured BMD in the lumbar vertebrae before, during, and after bedrest. After 60 d of bedrest, vertebral BMAT was higher in controls, +3.93% (95% CI: -0.28 to 8.14), compared to cAG and iAG interventions. After 60 d of bedrest, male controls BMAT increased 5.81% (95% CI: 2.01 to 9.61) compared to -1.35% (95% CI: -5.74 to 3.04) and 1.23% (95% CI: -1.53 to 3.99) for male cAG and iAG participants, respectively. This difference between interventions was significant: X2(2) = 8.487, p = .014. In addition, while control male participants showed decreased BMD after 60 d of bedrest (-0.02 g/cm2; 95% CI: -0.05 to 0.00), the male participants receiving iAG showed no decrease in BMD during bedrest (0.00 g/cm2; 95% CI: -0.04 to 0.05). The modulation of BMAT was inversely correlated with BMD at the same vertebrae. Recreating an axial force vector mechanically on horizontalized participants prevented BMAT accumulation and demineralization. These findings suggest exploring technological advances to translate these clinical benefits to populations at risk of acute or chronic bone loss.