title: "Bounce at the Bell": a novel program of short bouts of exercise improves proximal femur bone mass in early pubertal children.
abstract: OBJECTIVE
  To examine the effects of a simple and inexpensive physical activity intervention on change in bone mass and structure in school aged children.
  
  
  METHODS
  Fifty one children (n = 23 boys and 28 girls; mean age 10.1 years) participated in "Bounce at the Bell" which consisted of 10 counter-movement jumps 3x per day (total approximately 3 min/day). Controls were 71 matched children who followed usual school practice. We assessed dietary calcium, physical activity, physical performance, and anthropometry in September and after 8 months of intervention (June). We measured bone mineral content (BMC) and bone area at the lumbar spine, total body, and proximal femur. Proximal femur scans were also analysed for bone geometry and structural strength using the hip structural analysis program. Lean and fat mass (g) were also calculated.
  
  
  RESULTS
  Groups were similar at baseline and did not differ in weight, height, total body, lumbar spine, proximal femur, or femoral neck BMC. Control children had a greater increase in adjusted total body BMC (1.4%). Intervention children gained significantly more BMC at the total proximal femur (2%) and the intertrochanteric region (27%). Change in bone structural parameters did not differ between groups.
  
  
  CONCLUSIONS
  This novel, easily implemented exercise program, took only a few minutes each day and enhanced bone mass at the weight bearing proximal femur in early pubertal children. A large, randomised study of boys and girls should be undertaken powered to test the effectiveness of Bounce at the Bell in children at different stages of maturity, and in boys and girls independently.
authors.affiliation: University of British Columbia, 588-828 West 10th Ave, Vancouver, BC, V52 1L8, Canada. mckayh@interchange.ubc.ca
authors.forename: H A
authors.initials: HA
authors.lastname: McKay
authors.forename: L
authors.initials: L
authors.lastname: MacLean
authors.forename: M
authors.initials: M
authors.lastname: Petit
authors.forename: K
authors.initials: K
authors.lastname: MacKelvie-O'Brien
authors.forename: P
authors.initials: P
authors.lastname: Janssen
authors.forename: T
authors.initials: T
authors.lastname: Beck
authors.forename: K M
authors.initials: KM
authors.lastname: Khan
mesh_terms: D000704:Analysis of Variance; D000886:Anthropometry; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology; D015519:Bone Density / Q000502:physiology; D002136:Calcium, Dietary / Q000008:administration & dosage; D002648:Child; D015331:Cohort Studies; D015444:Exercise / Q000502:physiology*; D005260:Female; D005269:Femur / Q000378:metabolism*; D006173:Gymnastics / Q000502:physiology*; D006801:Humans; D008297:Male; D010809:Physical Fitness / Q000502:physiology; D011446:Prospective Studies; D011627:Puberty / Q000502:physiology; D016474:Weight-Bearing / Q000502:physiology
chemical_list: D002136:Calcium, Dietary