title: Influence of drop-landing exercises on bone geometry and biomechanical properties in prepubertal girls: a randomized controlled study.
abstract: We conducted a 28-week school-based exercise trial of single-leg drop-landing exercise with 42 girls (Tanner stage 1, 6-10 years old) randomly assigned to control (C), low-drop (LD), or high-drop (HD) exercise groups. The LD and HD groups performed single-leg drop-landings (three sessions/week and 50 landings/session) from 14 and 28 cm, respectively, using the nondominant leg. Single-leg peak ground-reaction impact forces in a subsample ranged between 2.5 and 4.4 times body weight. Dependent variables were bone geometry and biomechanical properties using magnetic resonance imaging. No differences (P > 0.05) were found among groups at baseline for age, stature, lean tissue mass (DXA--Lunar 3.6-DPX), leisure-time physical activity, average daily calcium intake, or measures of knee extensor or flexor torque. A series of ANOVA and ANCOVA tests showed no within- or between-group differences from baseline to posttraining. Group comparisons assessing magnitude of change in side-to-side differences in geometry (area cm(2)) and cross-sectional moment of inertia (cm(4)) at proximal, mid, and distal sites revealed negligible effect sizes. Our findings suggest that strictly controlled unimodal, unidirectional single-leg drop-landing exercises involving low to moderate peak ground-reaction impact forces do not influence geometrical or biomechanical measures in the developing prepubertal female skeleton.
authors.affiliation: Centre of Physical Activity Across the Lifespan, School of Exercise Science, Australian Catholic University (ACU National), Strathfield, NSW 2135, Australia. david.greene@acu.edu.au
authors.forename: David A
authors.initials: DA
authors.lastname: Greene
authors.forename: Peter N
authors.initials: PN
authors.lastname: Wiebe
authors.forename: Geraldine A
authors.initials: GA
authors.lastname: Naughton
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000222:Adaptation, Physiological / Q000502:physiology*; D001696:Biomechanical Phenomena; D002136:Calcium, Dietary / Q000008:administration & dosage; D002648:Child; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D005269:Femur / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology; D006801:Humans; D007717:Knee / Q000502:physiology; D008279:Magnetic Resonance Imaging; D011627:Puberty / Q000502:physiology*; D016059:Range of Motion, Articular; D019415:Torque
chemical_list: D002136:Calcium, Dietary