Changes in tibial bone microarchitecture in female recruits in response to 8 weeks of U.S. Army Basic Combat Training.
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BACKGROUND U S Army Basic Combat Training BCT is a physically demanding program at the start of military service Whereas animal studies have shown that increased mechanical loading rapidly alters bone structure there is limited evidence of changes in bone density and structure in humans exposed to a brief period of unaccustomed physical activity PURPOSE We aimed to characterize changes in tibial bone density and microarchitecture and serum based biochemical markers of bone metabolism in female recruits as a result of 8 weeks of BCT METHODS We collected high resolution peripheral quantitative computed tomography images of the distal tibial metaphysis and diaphysis 4 and 30 of tibia length respectively and serum markers of bone metabolism before and after BCT Linear mixed models were used to estimate the mean difference for each outcome from pre to post BCT while controlling for race ethnicity age and body mass index RESULTS 91 female BCT recruits volunteered and completed this observational study age 21 5 3 3 yrs At the distal tibia cortical thickness trabecular thickness trabecular number bone volume total volume and total and trabecular volumetric bone density vBMD increased significantly by 1 2 all p Under 0 05 over the BCT period whereas trabecular separation cortical tissue mineral density TMD and cortical vBMD decreased significantly by 0 3 1 0 all p Under 0 05 At the tibia diaphysis cortical vBMD and cortical TMD decreased significantly both 0 7 p Under 0 001 Bone strength estimated by micro finite element analysis increased by 2 5 and 0 7 at the distal tibial metaphysis and diaphysis respectively both p Under 0 05 Among the biochemical markers of bone metabolism sclerostin decreased 5 7 whereas bone alkaline phosphatase C telopeptide cross links of type 1 collagen tartrate resistance acid phosphatase and 25 OH D increased by 10 28 all p Under 0 05 CONCLUSION BCT leads to improvements in trabecular bone microarchitecture and increases in serum bone formation markers indicative of new bone formation as well as increases in serum bone resorption markers and decreases in cortical vBMD consistent with intracortical remodeling and or deposition of new less mineralized bone tissue This study demonstrates specific changes in trabecular and cortical bone density and microarchitecture following 8 weeks of unaccustomed physical activity in women