Original articles  NEUROPHYSIOLOGY 

The Journal of Sports Medicine and Physical Fitness 2004 March;44(1):98-103

Copyright © 2009 EDIZIONI MINERVA MEDICA

lingua: Inglese

The muscle strength and bone density relationship in young women: dependence on exercise status

Taaffe D. R. ¹, Marcus R. ²

¹ School of Human Movement Studies University of Queensland, Brisbane, Queensland, Australia 2 Department of Medicine Stanford University, Stanford, CA, USA

Aim. Numerous stud­ies ­report an asso­ci­a­tion ­between mus­cle ­strength and ­bone min­er­al den­sity (BMD) in ­young and old­er wom­en. However, the par­tic­i­pants are gen­er­al­ly non-ath­letes, ­thus it is ­unclear if the rela­tion­ship var­ies by exer­cise stat­us. Therefore, the pur­pose was to exam­ine the rela­tion­ships ­between BMD and mus­cle ­strength in ­young wom­en ­with mark­ed­ly dif­fer­ent exer­cise lev­els.
Methods. Experimental ­design: ­cross-sec­tion­al. Setting: a University ­research labor­a­to­ry. Participants: 18 col­le­giate gym­nasts and 22 age- and ­weight-­matched recrea­tion­al­ly ­active con­trol wom­en. Measures: lum­bar ­spine, femo­ral ­neck, arm, leg and ­whole ­body BMD (g/cm2) ­were ­assessed by ­dual X-ray absorp­tiom­e­try. In addi­tion, lum­bar ­spine and femo­ral ­neck ­bone min­er­al appar­ent den­sity (­BMAD, g/cm3) was cal­cu­lat­ed. Handgrip ­strength and ­knee exten­sor and flex­or ­torque (60°/s) ­were deter­mined by dyna­mom­e­try, and ­bench ­press and leg ­press ­strength (1-RM) ­using iso­ton­ic equip­ment.
Results. BMD at all ­sites and ­bench ­press, leg ­press and ­knee flex­or ­strength ­were great­er in gym­nasts ­than con­trols (p<0.001). In con­trols, ­knee exten­sor ­torque was sig­nif­i­cant­ly cor­re­lat­ed to femo­ral ­neck, ­limb and ­whole ­body BMD (r=0.47-0.55, p<0.05), leg ­press ­strength was asso­ciat­ed ­with ­limb and ­whole ­body BMD (r=0.52-0.74, p<0.05), and ­bench ­press ­strength ­with arm BMD (r=0.50, p=0.019). In par­tial cor­re­la­tions con­trol­ling for ­weight, leg ­press ­strength was relat­ed to leg and ­whole ­body BMD (r=0.46-0.63, p<0.05). There was no asso­ci­a­tion ­between mus­cle ­strength and BMD in gym­nasts.
Conclusion. These ­results sug­gest ­that the asso­ci­a­tion ­between mus­cle ­strength and BMD in ­young wom­en is depen­dent on exer­cise stat­us. The oste­o­gen­ic ­effect of ­increased mechan­i­cal load­ing asso­ciat­ed ­with gym­nas­tics train­ing like­ly con­trib­utes to the dis­so­ci­a­tion of the rela­tion­ship in gym­nasts.