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00005768-200305001-0041600005768_2003_35_s77_maclean_intervention_5miscellaneous< 18_0_5_0 >Medicine & Science in Sports & Exercise©2003The American College of Sports MedicineVolume 35(5) Supplement 1May 2003p S77“BOUNCE AT THE BELL”: THE EFFECTS OF A NOVEL EXERCISE INTERVENTION ON CHILDREN'S BONE MASS.[B-13L FREE COMMUNICATION/POSTER BONE AND CONNECTIVE TISSUE]MacLean, L B.1; MacKelvie, K J.1; Macdonald, H M.1; McKay, H A.11University of British Columbia, Vancouver, British Columbia(Sponsor: Karim M. Khan, FACSM)PURPOSEAs a guard against osteoporosis, maximizing childhood bone mineral accrual is critical. Results from our lab, and others, suggest that weight bearing exercise interventions of 10–20 mins, 3X/week elicit a positive osteogenic response after 7–9 months in several skeletal sites in children. However, whether shorter, more frequent bouts of exercise will have a similar osteogenic response in children in unknown.METHODSWe investigated bone mass changes in 28 girls and 23 boys (Tanner 1–3, 10.1 ± .5 yrs) who participated in an 8-month program of 10 jumps, 3X/day, 5 days/week and a control group, 46 girls and 41 boys, (Tanner stages 1–3, 10.2 ± .5 years old). We administered physical activity (PA), calcium intake (Ca) and maturity questionnaires at baseline and 8 months. We assessed bone mineral content (BMC) of the proximal femur (PF), lumbar spine (LS), and total body (TB) using dual energy x-ray absorptiometry (DXA)(Hologic, QDR 4500). We obtained lean and fat mass (gms) from DXA TB scans, and measured height (cm) and weight (kg) by standard methods.RESULTSThere was no difference between groups for age, HT, WT, maturity level, Ca or PA at baseline. Over 8 months, BMC at the intertrochanteric region (IT)(2.6%, p = .008) and proximal femur (PF)(3.2%, p = .012) increased significantly more in intervention children (ANCOVA, baseline height, change in height, final TS, final age and physical activity as covariates). BMC changes were not significant at other sites. All growth parameters changed similarly between groups.CONCLUSIONOur results demonstrate that frequent, short bouts of exercise elicit a positive osteogenic response on FN and IT BMC. Further study is required to investigate whether or not these changes are maintained 12 months after withdrawal of the exercise stimulus. Also, it is not known what bone strength and structural changes may occur at the proximal femur as an adaptation to loading. Early puberty may be a particularly responsive time for proximal femur adaptation to loading activity.&#8220;BOUNCE AT THE BELL&#8221;: THE EFFECTS OF A NOVEL EXERCISE INTERVENTION ON CHILDREN&apos;S BONE MASS.MacLean, L B.; MacKelvie, K J.; Macdonald, H M.; McKay, H A.B-13L Free Communication/Poster Bone and Connective Tissue535