Citation

Evans RK, Negus C, Antczak AJ, Yanovich R, Israeli E, Moran DS. Med. Sci. Sports Exerc. 2008; 40(11 Suppl): S645-53.

Affiliation

US Army Research Institute of Environmental Medicine, Natick, MA 01760, USA. rachel.evans@us.army.mil

Copyright

(Copyright © 2008, Lippincott Williams and Wilkins)

DOI

10.1249/MSS.0b013e3181893cb7

PMID

18849870

Abstract

BACKGROUND: Stress fracture (SF) injuries in new recruits have long been attributed to low bone mineral density (BMD). Low areal BMD assessed using two-dimensional dual-energy x-ray absorptiometry imaging, however, reflects structural density and is affected by smaller measures of bone geometry. Recent studies support a relationship between bone size and SF and indicate that slender bones are more susceptible to damage under identical loading conditions. Peripheral quantitative computed tomography (pQCT) is a three-dimensional imaging tool that provides measures of tissue density and geometry parameters of the tibia, a common site of SF. PURPOSE: To evaluate sex differences in parameters of volumetric BMD (vBMD), geometry, and strength of the tibia in new recruits using a novel pQCT image analysis procedure. METHODS: pQCT images were obtained from 128 healthy men and women (20 male, 108 female, aged 18-21 yr) entering a 4-month gender-integrated combat training program in the Israeli Defense Forces. Tibial scans taken at sites 4% (trabecular bone), 38%, and 66% (cortical bone) from the distal end plate were analyzed using MATLAB to assess whole-bone and regional parameters. Measures included vBMD, geometry (diameter, area, cortical thickness, and canal radius), and strength (moments of inertia and bone strength and slenderness indices). RESULTS: With the exception of normalized canal radius, which did not differ between sexes, all measures of bone geometry (P<0.0001) and strength (P<0.0001 to P = 0.07) were greater in men. Women exhibited 2.7% to 3.0% greater cortical vBMD than men, whereas trabecular vBMD was 8.4% lower in women (P<0.001). These differences remained significant after adjusting for body size. CONCLUSION: Sex differences in bone geometry and mineralization of the tibia may contribute to a decreased ability to withstand the demands imposed by novel, repetitive exercise in untrained individuals entering recruit training.

Language: en