The Lichfield bone study: the skeletal response to exercise in healthy young men

Abstract

The skeletal response to short-term exercise training remains poorly described. We thus studied the lower limb skeletal response of 723 Caucasian male army recruits to a 12-wk training regime. Femoral bone volume was assessed using magnetic resonance imaging, bone ultrastructure by quantitative ultrasound (QUS), and bone mineral density (BMD) using dual-energy X-ray absorptiometry (DXA) of the hip. Left hip BMD increased with training (mean ± SD: 0.85 ± 3.24, 2.93 ± 4.85, and 1.89 ± 2.85% for femoral neck, Ward's area, and total hip, respectively; all P < 0.001). Left calcaneal broadband ultrasound attenuation rose 3.57 ± 0.5% (P < 0.001), and left and right femoral cortical volume by 1.09 ± 4.05 and 0.71 ± 4.05%, respectively (P = 0.0001 and 0.003), largely through the rise in periosteal volume (0.78 ± 3.14 and 0.59 ± 2.58% for right and left, respectively, P < 0.001) with endosteal volumes unchanged. Before training, DXA and QUS measures were independent of limb dominance. However, the dominant femur had higher periosteal (25,991.49 vs. 2,5572 mm(3), P < 0.001), endosteal (6,063.33 vs. 5,983.12 mm(3), P = 0.001), and cortical volumes (19,928 vs. 19,589.56 mm(3), P = 0.001). Changes in DXA, QUS, and magnetic resonance imaging measures were independent of limb dominance. We show, for the first time, that short-term exercise training in young men is associated not only with a rise in human femoral BMD, but also in femoral bone volume, the latter largely through a periosteal response.

Fig. 1.

MRI image analysis was carried out using CMR-Tools. A: example of unmagnified image of left thigh in cross section. B: magnified image of the same left thigh cross section. The operator is able to magnify each bone image and outline the region of interest (ROI) free hand (for greater free-hand bone-edge contour accuracy, ROIs are only placed once the image has been greatly magnified). This process is repeated three times so as to obtain the three cross-sectional values described below. 1) Endostial volume (EV): analysis of this ROI alone gives the cross-sectional value for the femur within the boundaries of the inner bony cortex, referred to here as the EV when in series with other slices, or “endostial cross section” when considered for individual sections. 2) Cortical volume: with two ROIs in place, the software will calculate the cross section of cortical bone, referred to here as the “cortical volume” when in series with other slices, or “cortical cross section” when considered for individual sections. 3) Periostial volume (PV): analysis of this ROI alone gives the cross-sectional value for the femur within the boundaries of the outer bony cortex, referred to here as the PV when in series with other slices, or “periostial cross section” when considered for individual sections.