Changes in tibial bone microarchitecture in female recruits in response to 8 weeks of U.S. Army Basic Combat Training.
Bone. 2018 Apr 27;113:9-16. doi: 10.1016/j.bone.2018.04.021. [Epub ahead of print]
Hughes JM1, Gaffney-Stomberg E2, Guerriere KI2, Taylor KM2, Popp KL3, Xu C4, Unnikrishnan G4, Staab JS2, Matheny RW Jr2, McClung JP5, Reifman J4, Bouxsein ML6.
- 1 in 20 men, 1 in 5 women get stress fractures
- “...women with the greatest decline in cortical volumetric BMD from baseline to 8 weeks (mean, -9.26%) were more likely to have vitamin D deficiency at baseline vs. women with the least decline in cortical volumetric BMD (mean, 2.93%; P = .04)”
- Increased stress fractures during military training if low vitamin D (now in UK as well as US) – Jan 2016
- Stress fractures in basic training associated with 2.5 ng less vitamin D – meta-analysis Nov 2014
- Large decreases in Vitamin D and Iron during military basic training – March 2017
- Vitamin D prescriptions in US Military increased 5X in 5 years – July 2015
- Soldiers need vitamin D, but levels cut in half in 18 years – March 2014
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.
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.
We collected high-resolution peripheral quantitative computed tomographic images of the distal tibial metaphysis and diaphysis (4% and 30% of tibia length from the distal growth plate, 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.
91 female BCT recruits volunteered and completed this observational study (age = 21.5 ± 3.3 yrs). At the distal tibial metaphysis, 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 < 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 < 0.05). At the tibial diaphysis, cortical vBMD and cortical TMD decreased significantly (both -0.7%, p < 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 < 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 < 0.05).
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. Together, these results demonstrate specific changes in trabecular and cortical bone density and microarchitecture following 8 weeks of unaccustomed physical activity in women.
PMID: 29709620 DOI: 10.1016/j.bone.2018.04.021