Bone responses, assayed using histomorphometry, micro-computerized tomography and ELISA, after performance of either a LRLF, HRLF, LRHF and HRHF task for 12 weeks. (A-B) Number of osteoblast and osteoclasts, normalized by bone surface (N.Ob./BS and N.Oc/BS), assayed using histomorphometry. (C-D) Serum levels of CTX1 and osteocalcin, serum biomarkers of bone formation and bone resorption, respectively, assayed using ELISA. (D-H) Micro-computerized tomography (MicroCT) results for trabecular bone volume (BV/TV) of trabecular bone located in the distal radial metaphysis, as well as trabecular number (Tb.N), trabecular separation (Tb.Sp.) and trabecular thickness (Tb.Th). (I) Representative transaxial views of the trabecular region of the distal radial metaphysis, captured using microCT scanning and reconstruction and then 3-D rendering, showing a significant loss of trabeculae in this region in 12-week HRHF rats, but not in FRC or 12-week LRHF rats. This region shown was used to generate the BV/TV data shown in panel G. Symbols: aa: p < 0.01, compared to LRLF rats; bb: p < 0.01, compared to HRLF rats; dd: p < 0.01, compared to HRHF rats; **: p < 0.01, compared to food restricted control (FRC) rats (mean FRC values are indicated by dashed line). Mean and SEM are shown.