Effect of physical activity on bone mineralization in premature infants Laurie Moyer-Mileur, PhD, RD, CD, Maurie Luetkemeier, PhD, Lois Boomer, OTR, and Gary M, Chan, MD From the Departments of Pediatricsand Exercise and Sport Science, University of Utah, Salt Lake City, Utah Objective: A 4-week pilot study was done with 26 preterm infants to evaluate whether a physical activity program would result in greater bone mineralization. Design: Subjects were matched by birth weight, gender, and gestational age, and randomly assigned to the physical activity program (group EX; n = 13) or to the control group (group C; n = 13). Physical activity consisted of range of motion with passive resistance to all extremities for 5 to 10 minutes daily. Baseline and 4-week values were determined for both bone mineral analyses and serum levels of cal- cium, phosphate, alkaline phosphatase, parathyroid hormone, and 25-hydroxy- vitamin D. Results: Despite similar nutrient intake at advised levels for preterm infants, EX in- fants gained more weight than control subjects (I 7.8 vs 13.4 gm/kg body weight per day; p = 0.01). A difference in radial bone mass and density change as de- termined by single-beam photon absorptiometry (___2% error) was found between groups (p = 0.006 by analysis of covariance). Changes in bone width and in bone mineral content and density were enhanced by physical activity. Group EX infants had 12%, 18%, and 34% gains in bone width and in bone mineral density and content, respectively; group C infants had only a 2% gain in bone width and 1I% and 14% losses from baseline in bone mineral content and density, respectively, during the 4-week study. Serum biochemical values were similar in the groups except for lower alkaline phosphatase levels in group EX. There was a negative association between bone mineral content and parathyroid hormone values: r = -0.83, p = 0.01. Conclusions: A physical activity program may increase the effects of adequate nutrition in healthy preterm very low birth weight infants by promoting weight gain and bone mass and by decreasing the risk of osteopenia. (J PEDIATR 1995;127:620-5) Infants born prematurely are at risk of having osteopenia of prematurity and rickets because of both a limited accretion of bone mass in utero and greater need for bone nutrients than in infants delivered at term. 1-6 It is estimated that 50% of in- fants with birth weight <1000 gm will acquire osteopenia of prematurity; the subsequent fracture rate is 70%. 1, 5 Bone Presented in part at the Western Society for Pediatric Research, Carmel, Calif., 1995; abstract published in the Journal of Clinical Investigation, 1995. Supported in part by Public Health Services research grant No. MO 1-RR00064 from the National Center for Research Resources. Reprint requests: Laurie Moyer-Mileur, PhD, RD,CD, 2A210, Di" vision of Neonatology, University of Utah, Salt Lake City, UT 84132. Submitted for publication Jan. 26, 1995; accepted May 15, 1995. Copyright © 1995 by Mosby-Year Book, Inc. 0022-3476/95/$5.00 + 0 9/23/66274 BMC Bone mineral content BMD Bone mineral density BW Bone width C Control group EX Physical exercise group PTH Parathyroid hormone SPA Single-beam photon absorptiometry mineralization in premature infants does not approach nor- mal ranges until after the first year of life7 and may continue to be inadequate into childhood, further increasing the risk of fracture. 8 620