title: Neuromuscular performance and body mass as indices of bone loading in premenopausal and postmenopausal women.
abstract: The strong association between body mass and skeletal robusticity has been attributed to increasing skeletal loading with increasing mass. However, it is unclear whether body mass is merely a coarse substitute for bone loading rather than a true independent predictor of bone strength. As indices of neuromuscular performance, impulse and peak power were determined from vertical ground reaction force during a maximal counter movement jump test in 221 premenopausal and 82 postmenopausal women. Bone compressive (BSI(d) g(2)/cm(4)) and bending (SSImax(mid) mm(3)) strength indices were measured with peripheral quantitative computed tomography (pQCT) at the distal ((d)) and midshaft ((mid)) sites of the tibia. A two-step forced regression model for predicting bone strength indices was constructed. Age, height and body mass were entered first, followed by impulse as an indicator of skeletal loading. The basic model explained 14% (P<0.001) of the variance in BSI(d) in the premenopausal group and 16% (P=0.004) in the postmenopausal group, and 32% (P<0.001) and 25% (P<0.001) of the variance in SSImax(nud) respectively. Entering impulse into the model increased the explanatory power by 9% (P<0.001) and 7% (P<0.001) for BSI(d) and by 8% (P<0.001) and 12% (P<0.001) for SSImax(mid). Furthermore, impulse replaced body mass as an independent significant factor explaining the variance in bone strength. These results indicate that neuromuscular performance should be measured and preferred over body mass in models predicting skeletal robusticity.
authors.affiliation: Department of Biology of Physical Activity, University of Jyväskylä, Finland. timo.j.rantalainen@jyu.fi
authors.forename: Timo
authors.initials: T
authors.lastname: Rantalainen
authors.forename: Riku
authors.initials: R
authors.lastname: Nikander
authors.forename: Ari
authors.initials: A
authors.lastname: Heinonen
authors.forename: Juhani
authors.initials: J
authors.lastname: Multanen
authors.forename: Arja
authors.initials: A
authors.lastname: Häkkinen
authors.forename: Timo
authors.initials: T
authors.lastname: Jämsä
authors.forename: Ilkka
authors.initials: I
authors.lastname: Kiviranta
authors.forename: Vesa
authors.initials: V
authors.lastname: Linnamo
authors.forename: Paavo V
authors.initials: PV
authors.lastname: Komi
authors.forename: Harri
authors.initials: H
authors.lastname: Sievänen
mesh_terms: D000328:Adult; D000367:Age Factors; D001823:Body Composition / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D019245:Compressive Strength / Q000502:physiology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D009068:Movement / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology*; D010003:Osteoarthritis / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005082:Physical Exertion / Q000502:physiology; D017698:Postmenopause / Q000502:physiology*; D017697:Premenopause / Q000502:physiology*; D011859:Radiography; D012044:Regression Analysis; D013314:Stress, Mechanical; D013977:Tibia / Q000000981:diagnostic imaging / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology