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Keywords:

  • exercise;
  • calcium;
  • growth;
  • BMC;
  • boys

Abstract

We examined the combined effects of exercise and calcium on BMC accrual in pre- and early-pubertal boys. Exercise and calcium together resulted in a 2% greater increase in femur BMC than either factor alone and a 3% greater increase in BMC at the tibia–fibula compared with the placebo group. Increasing dietary calcium seems to be important for optimizing the osteogenic effects of exercise.

Introduction: Understanding the relationship between exercise and calcium during growth is important given that the greatest benefits derived from these factors are achieved during the first two decades of life. We conducted a blinded randomized-controlled exercise–calcium intervention in pre- and early-pubertal boys to test the following hypotheses. (1) At the loaded sites (femur and tibia–fibula), exercise and calcium will produce greater skeletal benefits than either exercise or calcium alone. (2) At nonloaded sites (humerus and radius–ulna), there will be an effect of calcium supplementation.

Materials and Methods: Eighty-eight pre- and early-pubertal boys were randomly assigned to one of four study groups: moderate impact exercise with or without calcium (Ca) (Ex + Ca and Ex + placebo, respectively) or low impact exercise with or without Ca (No-Ex + Ca and No-Ex + Placebo, respectively). The intervention involved 20 minutes of either moderate- or low-impact exercise performed three times a week and/or the addition of Ca-fortified foods using milk minerals (392 ± 29 mg/day) or nonfortified foods over 8.5 months. Analysis of covariance was used to determine the main and combined effects of exercise and calcium on BMC after adjusting for baseline BMC.

Results: At baseline, no differences were reported between the groups for height, weight, BMC, or bone length. The increase in femur BMC in the Ex + Ca group was ∼2% greater than the increase in the Ex + placebo, No-Ex + Ca, or No-Ex + Placebo groups (all p < 0.03). At the tibia–fibula, the increase in BMC in the Ex + Ca group was ∼3% greater than the No-Ex + placebo group (p < 0.02) and 2% greater than the Ex + Placebo and the No-Ex + Ca groups (not significant). No effect of any group was detected at the humerus, ulna–radius, or lumbar spine for BMC, height, bone area, or volume.

Conclusions: In this group of normally active boys with adequate calcium intakes, additional exercise and calcium supplementation resulted in a 2–3% greater increase in BMC than controls at the loaded sites. These findings strengthen the evidence base for public health campaigns to address both exercise and dietary changes in children for optimizing the attainment of peak BMC.