The Effect of Assisted Exercise Frequency on Bone Strength in Very Low Birth Weight Preterm Infants: A Randomized Control Trial

Abstract

We aimed to assess whether a twice daily assisted exercise interventional program will have a greater effect on bone strength compared to a once daily intervention or no intervention in very low birth weight (VLBW) preterm infants. Thirty-four very VLBW preterm infants (mean BW 1217±55g and mean gestational age 28.6±1.1weeks) were randomly assigned into one of three study groups: twice daily interventions (n=13), a once daily intervention (n=11), and no intervention (control, n=10). The intervention was initiated at a mean of 8±2.4days of life and continued for 4weeks. It included passive extension and flexion range-of-motion exercise of the upper and lower extremities. Bone strength was measured at enrollment and after 2 and 4weeks using quantitative ultrasound of tibial bone speed of sound (SOS, Sunlight Omnisense™). At enrollment, the mean bone SOS was comparable between the twice daily interventions, once daily intervention and control groups (2918±78, 2943±119, and 2910±48m/s, respectively). As expected, the bone SOS declined in all groups during the study period (-23.6±24, -68.8±28, and -115.8±30m/s, respectively, p<0.05), with a significantly attenuated decrease in bone strength in the twice daily intervention group (p=0.03). A twice daily intervention program of assisted range-of-motion exercise attenuates the decrease in bone strength and may decrease the risk of osteopenia and future fractures in VLBW preterm infants.