title: Sexual dimorphism in bone-muscle relationship in young adults.
abstract: The purpose of this study was to analyse associations between lean soft tissue (LST), a surrogate of skeletal muscle mass and key fracture-related geometric characteristics of the proximal femur. Moreover, we examined the role that muscle played on the proximal femur geometry in response to physical activity (PA). Participants were 83 young adults. Leg LST (exposure) was assessed by dual energy X-ray absorptiometry (DXA). Proximal femur geometry was derived from a left hip DXA scan. Geometric variables (outcomes) included the femoral neck axis length (FNAL), the femoral neck width (FNW), the neck-shaft angle and FNW|FNAL (an index of robustness). PA was evaluated by accelerometry. Linear regression was used to analyse relationships. Additional exposure variables included body height and mass. In males, leg LST explained 17.4% of variation in FNAL (P < 0.001) and 15% in FNW (P = 0.015). In females, it explained 8.8% of the variance in FNAL (P = 0.020). Associations remained significant in males, but not in females, when vigorous PA was added to the models. These results suggest that public health approaches to promote PA may be particularly important in females since vigorous PA seems to convey advantages in femur geometry and consequently in bone strength.
authors.affiliation: a Exercise and Health Laboratory, CIPER, Faculdade de Motricidade Humana , Universidade de Lisboa , Lisbon , Portugal.
authors.forename: Vera
authors.initials: V
authors.lastname: Zymbal
authors.affiliation: b Department of Health and Human Physiology and Department of Epidemiology , University of Iowa , Iowa City , IA , USA.
authors.forename: Kathleen F
authors.initials: KF
authors.lastname: Janz
authors.affiliation: a Exercise and Health Laboratory, CIPER, Faculdade de Motricidade Humana , Universidade de Lisboa , Lisbon , Portugal.
authors.forename: Fátima
authors.initials: F
authors.lastname: Baptista
mesh_terms: D015502:Absorptiometry, Photon; D050218:Body Fat Distribution; D015992:Body Mass Index; D015519:Bone Density / Q000502:physiology*; D002136:Calcium, Dietary / Q000008:administration & dosage; D003238:Connective Tissue / Q000033:anatomy & histology; D015444:Exercise / Q000502:physiology*; D005260:Female; D005269:Femur / Q000033:anatomy & histology*; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology*; D012727:Sex Characteristics; D013314:Stress, Mechanical; D055815:Young Adult
chemical_list: D002136:Calcium, Dietary
keywords: Lean soft tissue; bone geometry; hip; physical activity; proximal femur