Background: Very low birth weight (VLBW) infants are at increase risk for osteopenia because of limited accretion of bone mass in utero, and greater need for bone nutrients. Previous studies have demonstrated that once daily passive range-of-motion exercise is beneficial for bone development in VLBW preterm infants. However, the optimal duration and frequency is yet unknown.
The aim of this study was to assess whether twice a-day exercise intervention will have greater effect on bone strength compared to once daily, or to no intervention.
Methods: Thirty four infants (birth weight 1217 ± 55 g and gestational age 28.6 ± 1.1 weeks, mean±SD) were randomly assigned into one of 3 study groups: twice a day intervention (group 1, n=13), once a day intervention (group 2, n=11) and control (group 3, n=10). The intervention started at mean 8±2.4 day of life, continued for 4 weeks, and included passive extension and flexion range-of-motion exercise of the upper and lower extremities. Bone strength was assessed at enrollment and after four weeks. by quantitative ultrasound measurement of tibial bone speed of sound (SOS, Sunlight OmnisenseTM).
Results: At enrollment, mean bone SOS was comparable between the three study groups (2918±78, 2944±125, 2898±29 m/sec respectively). During the study period bone SOS declined in all groups (-115.8 ±30, -68.8± 28 and -23.6±24 m/second respectively, ANOVA p<0.05), with significant difference between the control and the twice a day intervention group (p=0.027).
Conclusion: Twice a day intervention of assisted range-of-motion exercise attenuates the decrease in bone strength and may decrease the risk of osteopenia in premature infants.
