Reduced postural stability in men and women aged 55-65 following 14 days of head-down bed rest

Aging and head-down bed rest (HDBR) decrease postural stability. Chances of being bedridden increase with age, but HDBR studies usually focus on young men. Here, we evaluate the impact of HDBR on postural stability among late middle-aged individuals. Twenty-two healthy participants (55-65 years old, 11 women) were exposed to 14-day HDBR. Eleven participants performed daily exercise. Static posturography data were collected before, 5 h after, and 4 weeks after HDBR. No time×group or time×sex effects were observed, but women had lower postural stability. With eyes open, the root mean square of the center of pressure was larger immediately after HDBR only in the medio-lateral axis (median [interquartile range]: +53% [+ 15%; +129%], p = 0.002). The mean velocity was increased on both axes (+ 20% [+ 8%; +46%] for medio-lateral and + 19% [+ 13%; +36%] for antero-posterior, both p < 0.001). The complexity features and the critical time were left unchanged. The effects of HDBR were more visible in the eyes open condition and the deconditioning was reversible after four weeks. 14-day HDBR decreased postural stability in individuals aged 55-65, with no impact of the chosen countermeasure. While the deconditioning was equivalent to two decades of aging for some features, additional research is required to determine whether age was an aggravating factor.