Bone Mineral Response to a 7-Month Randomized Controlled, School-Based Jumping Intervention in 121 Prepubertal Boys: Associations With Ethnicity and Body Mass Index

Authors

  • K. J. Mackelvie,

    1. School of Human Kinetics, University of British Columbia, Vancouver, Canada
    Search for more papers by this author
  • H. A. Mckay Ph.D.,

    Corresponding author
    1. School of Human Kinetics, University of British Columbia, Vancouver, Canada
    • School of Human Kinetics, University of British Columbia, 6081 University Boulevard, Vancouver, BC, Canada V6T 1Z1
    Search for more papers by this author
  • M. A. Petit,

    1. School of Human Kinetics, University of British Columbia, Vancouver, Canada
    2. Department of Health Evaluation Sciences, Penn State University College of Medicine, Hershey, Pennsylvania, USA
    Search for more papers by this author
  • O. Moran,

    1. Faculty of Medicine, Universidad Autónoma de San Luis Potosí, San Luis Potosí, México
    Search for more papers by this author
  • K. M. Khan

    1. School of Human Kinetics, University of British Columbia, Vancouver, Canada
    2. Faculty of Medicine, Department of Family Practice, University of British Columbia, Vancouver, Canada
    Search for more papers by this author

  • The authors have no conflict of interest

Abstract

We examined the effects of a 7-month jumping intervention (10 minutes, 3 times per week) on bone mineral gain in prepubertal Asian and white boys (10.3 ± 0.6 years, 36.0 ± 9.2 kg) at 14 schools randomized to control (n = 60) and intervention (n = 61) groups. Intervention and control groups had similar mean baseline and change in height, weight, lean mass and fat mass, baseline areal bone mineral density (aBMD; g/cm2), bone mineral content (BMC; g; dual-energy X-ray absorptiometry [DXA], QDR 4500W), and similar average physical activity and calcium intakes. Over 7 months, the intervention group gained more total body (TB) BMC (1.6%, p < 0.01) and proximal femur (PF) aBMD (1%, p < 0.05) than the control group after adjusting for age, baseline weight, change in height, and loaded physical activity. We also investigated the 41 Asian and 50 white boys (10.2 ± 0.6 years and 31.9 ± 4.4 kg) who were below the 75th percentile (19.4 kg/m2) of the cohort mean for baseline body mass index (BMI). Boys in the intervention group gained significantly more TB and lumbar spine (LS) BMC, PF aBMD, and trochanteric (TR) aBMD (+ ∼2%) than boys in the control group (adjusted for baseline weight, final Tanner stage, change in height, and loaded physical activity). Bone changes were similar between Asians and whites. Finally, we compared the boys in the control group (n = 16) and the boys in the intervention group (n = 14) whose baseline BMI fell in the highest quartile (10.5 ± 0.6 years and 49.1 ± 8.2 kg). Seven-month bone changes (adjusted as aforementioned) were similar in the control and intervention groups. In summary, jumping exercise augmented bone mineral accrual at several regions equally in prepubertal Asian and white boys of average or low BMI, and intervention effects on bone mineral were undetectable in high BMI prepubertal boys.

Ancillary