Physical Activity, Calcium, and Bone in Children
Condition: Physical Activity; Nutrition
Study type: Interventional
Phase: Phase 2

Summary: 
      Doctors recommend that young children participate in daily physical activity to promote bone
      health. However, studies in adults show that physical activity and increased calcium intake
      cause noticeable benefits for bone health only when both factors occur together. The goal of
      this study is to find out whether calcium intake changes the response of bone to activity in
      children 3 to 4 years old. Children will participate in one of two programs conducted in
      childcare centers 5 days a week for 1 year. One program will involve activities that use
      large muscles (gross motor activity). The other will involve activities using small muscles
      (fine motor activity). We will give a calcium supplement (1 gram per day) to half of the
      children in each program and give the other half an inactive pill. We will measure bone mass
      and bone mineral density at the beginning and end of the study. We will take measurements 12
      months after the program's completion to see if physical activity and/or calcium supplements
      have long-term effects on bone mineral density and physical activity.
    

Detailed description: 
      Participation in daily physical activity programs by young children is currently recommended
      as a means of promoting bone health. Results from studies of adults indicate that beneficial
      effects of either physical activity or calcium (Ca) intake may be apparent only when both
      these factors are present. Our results in infants indicate that physical activity combined
      with a low Ca diet may be detrimental in terms of bone mass accretion. The overall objective
      of this study is to determine whether Ca intake modifies the bone response to activity in
      young children 3 to 4 years of age.

      Our hypotheses are that (1) the increase in bone mass resulting from a physical activity
      program will be more pronounced in children randomized to receive a Ca supplement compared to
      the increase in children randomized to receive a placebo; and (2) 12 months after cessation
      of the activity program, bone mass will remain higher in children randomized to gross motor
      activity compared to children randomized to fine motor activity, and the beneficial effect of
      Ca supplementation will persist only among children randomized to gross motor activity. We
      will test these hypotheses in a randomized 2 x 2 factorial trial in 3- to 4-year-old
      children. We will randomize children into either a gross motor or fine motor activity program
      that will be conducted in childcare centers 5 days a week for 1 year. We will further
      randomize each child into either a Ca supplement (1 g/d) or placebo group.

      The primary outcomes of the study are bone mass accretion and changes in bone mineral
      density, which we will determine by dual energy x-ray absorptiometry at the beginning and end
      of the study. We will do activity assessments throughout the study period to determine
      whether participation in the gross motor activity group also increases spontaneous activity
      in these children. Anthropometric measurements and dietary information will allow us to
      statistically control for these potential confounders. We will obtain additional bone mass
      and physical activity measurements 12 months after completion of the program to determine if
      these interventions have long-term effects on bone mineral density and physical activity.

      A finding of beneficial effects of Ca supplementation or physical activity, either
      independent of each other or in combination, will lay the groundwork for devising prevention
      strategies within the educational system that optimize bone health beginning early in life.
      However, we may find that increased physical activity in the presence of a low to moderate Ca
      intake may have a detrimental effect on bone mass accretion during periods of rapid growth.
    

Intervention name(s): Physical activity; Calcium supplement
Intervention type(s): Procedure; Drug
Intervention MeSH terms: Calcium
Allocation: Randomized
Intervention model: Factorial Assignment
Masking: Double
Primary purpose: Prevention
Keywords: Calcium; Physical activity; Children; Bone mass accretion; Bone mineral density (BMD); Bone response to activity and calcium supplements; Placebo; Bone growth