The effects of exercise on body weight and circulating leptin in premature infants. Effects of motor physical therapy on bone mineralization in premature infants: a randomized controlled study. Assisted exercise and bone strength in preterm infants. Effect of physical activity on bone mineralization in premature infants. Early physical activity intervention prevents decrease of bone strength in very low birth weight infants. Daily physical activity program increases bone mineralization and growth in preterm very low birth weight infants. Evidence for exercise-induced bone formation in premature infants.
To assess the effect of daily movements on weight gain, serum leptin, and insulin-like growth factor I (IGF-I) in premature infants.
                Twenty very-low-birth-weight premature infants were matched and randomized to a daily movement (n = 10) and control groups (n = 10). Daily movement consisted of passive range of motion with gentle compression of both the upper and lower extremities 5 days per week for 4 weeks.
                Daily movements led to a significant increase in weight gain (784 +/- 51 vs 608 +/- 26 g in movements and controls, respectively, p < 0.02), and to a significant increase in leptin (0.60 +/- 0.19 vs 0.13 +/- 0.06 ng/ml in movements and controls, respectively 18.8 +/- 4.1 vs 9.2 +/- 4.1 ng/ml in movements and controls, respectively); however, this increase was not statistically significant.
                A relatively brief range of motion daily movement intervention was associated with greater weight gain and increased leptin levels in very-low-birth-weight premature infants. This may suggest that at least part of the daily movements associated with increase in body weight resulted from an increase in adipose tissue. To study the effect of physical therapy on bone mineralization, weight gain and growth in preterm infants.
                After fulfilling the inclusion criteria, preterm infants were matched for gestational age and birth weight and then randomly assigned to the physiotherapy group (PG, n=15) and control group (CG, n=14). The PG received motor physical therapy for 15 min daily, 5 times per week until hospital discharge. Bone mineralization was measured by total body dual energy X-ray beam absorptiometry (DEXA) at the onset and end of the study. Statistical analysis was realized by ANCOVA and linear correlation tests.
                The physical therapy group (PG) presented greater body weight gain per day (27.4+/-2.4 vs 21.01+/-4.4 g, P<0.001) and length (1.3+/-0.3 vs 0.8+/-0.2 cm week(-1), P<0.001) than did the control group (CG). Body composition values verified by DEXA were greater for the PG. The mean gain in bone mineral content (BMC) (mg) was greater in the PG (434+/-247.5 vs -8.9+/-11.4, P<0.001), as was the mean bone mineral density (BMD) gain (mg cm(-2)) (8.4+/-5.6 vs -3.1+/-5.5, P<0.001). The gain in bone area (BA,cm(2)) was 10.3+/-5 in the PG vs 1.5 +/-2 in the CG (P<0.001). The gain in lean mass (LM) (g) in the PG was also greater than in the CG (271.1+/-21.4 vs 109.1+/-1.0, P<0.009). The fat mass (g) was similar between the groups (P=0.432).
                These results showed that physiotherapy in preterm infants produced greater gains in growth, body weight, BMC, BMD, BA and LM. Studies have previously demonstrated that brief (4 weeks) passive range-of-motion exercise is beneficial for bone development in very low birth weight (VLBW) preterm infants. However, the optimal duration of exercise for bone development in preterm infants is yet unknown. The aim of the present study was to examine the effect of 8 weeks of assisted exercise on bone strength and metabolism in VLBW premature infants. Sixteen infants (mean +/- standard error of the mean birth weight 1,009 +/- 55 g and gestational age 27.3 +/- 0.3 weeks) were randomly assigned into exercise (n = 8) and control (n = 8) groups. The intervention started at the first week of life and involved 8 weeks of daily passive extension and flexion range-of-motion exercise of the upper and lower extremities. Biochemical markers of bone turnover were measured at enrollment and after 8 weeks. Bone strength was measured weekly by quantitative ultrasound measurement of tibial bone speed of sound (SOS). Bone SOS decreased significantly in the control group (-108.1 +/- 33.7 m/second, P < 0.0001) during the study period, while remaining stable in the exercise group (11.3 +/- 22.8 m/second). The main beneficial effect of exercise occurred in the first 4 weeks of the intervention. There were no significant differences in the bone turnover marker changes between the groups. There is a significant postnatal decrease in bone SOS in VLBW preterm infants. Eight weeks of assisted range-of-motion exercise attenuates the decrease in bone strength and may decrease the risk of osteopenia in premature infants. A 4-week pilot study was done with 26 preterm infants to evaluate whether a physical activity program would result in greater bone mineralization.
                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 calcium, phosphate, alkaline phosphatase, parathyroid hormone, and 25-hydroxy-vitamin D.
                Despite similar nutrient intake at advised levels for preterm infants, EX infants gained more weight than control subjects (17.8 vs 13.4 gm/kg body weight per day; p = 0.01). A difference in radial bone mass and density change as determined 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 11% 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.
                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. To evaluate the effect of early range-of-motion intervention on bone strength and bone turnover in very low birth weight infants.
                Twenty-four infants (mean birth weight: 1135 +/- 247 g; mean gestational age: 28.5 +/- 2.3 weeks) were matched for gestational age and birth weight and then randomly assigned into exercise (n = 12) and control (n = 12) groups. Exercise protocol started at the first week of life and involved daily extension and flexion range of motion against passive resistance of the upper and lower extremities (5 minutes per day, 5 days per week, 4 weeks). Growth parameters, bone strength, and biochemical markers of bone homeostasis were measured at enrollment and after 4 weeks. Bone strength was determined using quantitative ultrasound measurement of bone speed of sound (SOS) at the middle left tibial shaft.
                Bone SOS decreased significantly in the control group during the study period (from 2892 +/- 30 m/sec to 2799 +/- 26), whereas bone SOS of the exercise group remained stable (2825 +/- 32 m/sec and 2827 +/- 26 m/sec at baseline and 4 weeks, respectively). This significant difference in bone SOS was not expressed in the biochemical markers of bone homeostasis.
                There is a significant postnatal decrease in the bone SOS of very low birth weight infants. A brief range-of-motion exercise attenuates the decrease in bone strength and may decrease the risk of osteopenia. A study of daily physical activity was performed with 32 preterm infants to evaluate changes in body weight and bone mineralization.
                Subjects were matched by birth weight and gestational age and randomly assigned to the physical activity (PA; n = 16) or to the control (C; n = 16) program. PA consisted of range of motion against passive resistance to all extremities for 5 to 10 minutes daily. Peripheral dual-energy x-ray of the right forearm (ulna and radius); biomarkers of bone formation (serum type I collagen C-terminal propeptide [PICP]) and resorption (urine pyridinoline cross-links of collagen [Pyd]); serum calcium, phosphate, alkaline phosphatase, parathyroid hormone (PTH), and 1, 25-(OH)(2) vitamin D; and urine levels of calcium, phosphate, and creatinine were obtained. All measurements were made at study entry and at 2.0 kg of body weight.
                Despite a similar nutrient intake at advised levels for preterm infants, gains in body weight (g) and forearm bone length (cm), bone area (BA; cm(2)), bone mineral content (BMC; mg), and fat-free mass (g) were greater in PA infants. Forearm bone mineral density and fat mass gains did not differ between groups. Serum PICP levels remained constant in PA infants but decreased in C infants suggesting a slower rate of bone formation. Urine Pyd or bone resorption activity was similar between groups. A higher level of serum PTH was observed in PA infants at 2. 0 kg of body weight; however, the change from study entry to completion did not differ between groups. All other serum and urine values were similar and within normal limits.
                A daily PA program promotes greater gains in body weight, forearm length, BA, BMC, and fat-free mass in premature infants. We assessed the effect of a four weeks exercise training intervention on bone turnover markers in premature infants. Twenty-four very low birth weight premature infants were matched for gestational age, birth weight, gender, as well as for corrected age and weight at initiation of the study. Then the subjects were randomly divided into an exercise (n = 12) and a control group (n = 12). Exercise consisted of passive range of motion exercise with gentle compression of both the upper and lower extremities lasting 5 - 10 minutes each day, 5 days per week for 4 weeks. This protocol has been shown to increase bone mineral density in premature infants. Bone formation was assessed by measurements of circulating bone specific alkaline phosphatase (BSAP) and the C-terminal procollagen peptide (PICP). Bone resorption was determined by serum measurements of C- terminal cross-links telopeptide of type-I collagen (ICTP). Training led to a significant (P < 0.05) increase in weight gain (767 +/- 49 versus 586 +/- 24 gr in trained and control premature infants, respectively); and to a significant increase in BSAP (37.2 +/- 14.6 versus 4.1 +/- 8.4 % in trained and control premature infants, respectively). PICP increased also following exercise (34.6 +/- 18.9 versus 5.4 +/- 9.1 % in trained and control subjects, respectively), however, this increase was not statistically significant. Exercise led to a significant decrease in ICTP (-24.7 +/- 3.1 versus -5.5 +/- 5.4 % in trained and control subjects, respectively). A relatively brief exercise intervention was associated with a biochemical evidence of bone formation in very low birth weight premature infants.
There is some evidence that physical activity programs might promote short-term weight gain and bone mineralization in preterm infants. Data is inadequate to assess harm or long-term effects. Current evidence does not support the routine use of physical activity programs in preterm infants. Further trials incorporating infants with a high baseline risk of osteopenia are required. These trials should address adverse events, long-term outcomes, and the effects of nutritional intake (calories, protein, calcium, phosphorus).