Table 4. Dynamic histomorphometry of cortical bone in growing rats. Values are means (±SEM). 1-Week 2-Week 4-Week 8-Week L1 C1 L2 C2 L4 C4 L8 C8 Femur n=12 n=12 n=12 n=12 n=12 n=12 n=12 n=12    Periostium       MS/BS 36.6 (3.6) 32.6 (2.6) 41.2 (4.7) 39.9 (4.5) 43.2 (4.9) 34.0 (4.8) 33.0 (4.7) 36.2 (2.8)       MAR 1.8 (.79) 3.0 (.73) 2.9 (.94) 2.3 (.6) 1.7 (.40) 2.3 (.44) 1.5 (.43) 1.8 (.47)       BFR/BS .83 (.38) 1.07 (.25) 1.42 (.46) 1.07 (.34) .87 (.22) .90 (.19) .57 (.18) .75 (.21)    Endosteum       MS/BS 37.3 (3.9) 41.5 (5.4) 39.3 (3.0) 35.2 (3.5) 38.4 (5.9) 36.9 (4.8) 27.5 (6.6) 21.7 (4.2)       MAR 1.3 (.57) 3.4 (.93) 1.3 .64) 1.6 (.54) 1.4 (.32) 1.6 (.32) 1.7 (.33) 1.9 (.68)       BFR/BS .64 (.31) 1.70 (.45) .62 (.35) .74 (.28) .70 (.17) .72 (.16) .55 (.15) .50 (.15) Tibia n=12 n=12 n=12 n=12 n=12 n=12 n=12 n=12    Periostium       MS/BS 40.3 (2.0) 30.2 (3.3)* 40.1 (3.8) 37.9 (3.6) 35.4 (2.6) 28.3 (3.2) 21.5 (3.9) 29.0 (2.7)       MAR 1.0 (.41) .6 (.32) 1.2 (.53) 1.0 (.38) .8 (.34) .5 (.29) .7 (.40) .7 (.35)       BFR/BS .42 (.18) .23 (.13) .61 (.27) .48 (.19) .35 (.16) .19 (.11) .27 (.15) .19 (.11)    Endosteum       MS/BS 37.8 (5.4) 28.1 (3.4) 35.0 (3.8) 39.2 (3.5) 37.6 (4.2) 38.4 (3.9) 27.5 (4.7) 32.5 (3.3)       MAR 1.7 (.62) 1.1 (.45) 1.5 (.70) 1.3 (.39) 1.7 .(43) 1.7 (.52) 1.0 (.45) 1.2 (.36)       BFR/BS .84 (.32) .43 (.20) .69 (.33) .57 (.19) .73 (.20) .72 (.22) .38 (.24) .45 (.14) *, significant difference was shown between landing group to the time-matched sedentary control group, p < 0.05. BFR/BS, bone formation rate per bone surface, µm3/µm2/day; MAR, mineral apposition rate, µm/day. MS/BS, bone mineralization over bone surface, %.