Possible information on how mechanical stimulation can alter the bone.
“Tibial bone density and geometry were measured in 90 British Army male recruits (ages 21±3years, height: 1.78±0.06m, body mass: 73.9±9.8kg) in weeks 1 (Baseline) and 10 of initial military training. Scans were performed at the 4%, 14%, 38% and 66% sites, measured from the distal end plate, using pQCT (XCT2000L, Stratec Pforzheim, Germany). Customised software (BAMPack, L-3 ATI) was used to examine whole bone cross-section and regional sectors. T-tests determined significant differences between time points (P<0.05).
Bone density of trabecular and cortical compartments increased significantly at all measured sites. Bone geometry (cortical area and thickness) and bone strength (i, MMi and BSI) at the diaphyseal sites (38 and 66%) were also significantly higher in week 10. Regional changes in density and geometry were largely observed in the anterior, medial-anterior and anterior-posterior sectors. Calf muscle density and area (66% site) increased significantly at week 10 (P<0.01).
In vivo mechanical loading improves bone strength of the human tibia by increased density and periosteal expansion, which varies by site and region of the bone. These changes may occur in response to the nature and distribution of forces originating from bending, torsional and shear stresses of military training. These improvements are observed early in training when the osteogenic stimulus is sufficient, which may be close to the fracture threshold in some individuals.”
” The purpose of this training is to improve physical fitness and teach recruits basic military skills. In a 10-week period, infantry recruits typically undertake 27 periods of military drill, 45 physical training periods comprising of 8 continuous runs, 9 loaded marches (starting at 2 miles carrying a 10 kg backpack building up to 5 miles carrying a 20 kg backpack), 6 swimming sessions and 22 40-min periods of military specific fitness (obstacle course, circuit training, and steeplechase run).”
“There was no significant change in endosteal perimeter at any measured site.”
“Military activities that are not performed often, but likely exceed the strain threshold, include downhill running and/or zigzag motions, which elicit up to 2000 microstrain at the tibial shaft”