Calcium Kinetics during Bed Rest with Artificial Gravity and Exercise Countermeasures

To assess the potential for artificial gravity (AG) and exercise (EX) to mitigate the effects of bone loss during space flight, we performed two studies: (1) a 21‐d bed rest (BR) with subjects receiving 1 h/d AG (n=8) or no AG (n=7) and (2) a 28‐d BR with 1 h/d resistance EX (n=10) or no EX (n=3). In both studies, stable isotopes of Ca were administered orally and intravenously, at baseline and after 10 d of BR, and blood, urine, and feces were...