Trial design

This prospective randomized clinical trial was performed in the neonatal service department of the HUCVA; from February 2016 to July 2020, 46 preterm infants participated in it and were randomized into three intervention groups, two treatment groups and a control group. This study was approved by the HUCVA ethical committee for clinical research, using all the procedures stipulated in the Declaration of Helsinki41. This study has been registered at under identification number NCT04356807.


The participants in this study were preterm infants born between the 29th and the 34th + 2 weeks of gestational age (GA) who were admitted to the neonatal unit, with haemodynamic stability and full enteral nutrition, whose parents or guardians signed the consent form authorizing the participation of their infant in this study. New-borns with neurological disorders, a need for mechanical ventilation, bronchopulmonary dysplasia, congenital malformations, metabolic diseases, genetic diseases, intraventricular haemorrhage III-IV, those taking diuretic or corticosteroid medication, and those with bone fractures at the time of randomization were excluded.


The participants in this study were divided into three groups that, along with standard nursing care, received different physiotherapy treatments.

The control group (CG) was given limb and core massage, with gentle deep pressures and caresses lasting 15 min a day in a single physiotherapy session, 5 days per week, for 4 weeks, which was considered a placebo since this intervention has no influence on bone mineralization30,31,32,33,34,42.

The experimental group (EGpmc) received passive movements with gentle compression (PMC) as described by Moyer-Mileur et al.14 and with the adaptations of Vignochi et al.12 in a 15-min physiotherapy session, 5 days per week for 4 weeks. These mobilizations consist of flexion and extension movements in all the joints of both the upper and lower extremities and ending with chest movements following the baby's respiratory pace.

The experimental group (EGrlt) received RLT according to the procedures used by other authors18,19,20,21 for 16 min, as divided into two physiotherapy sessions of 8 min each, 5 days per week for 4 weeks. The exercises corresponding to the motor complexes of the 1st phase of reflex rolling and reflex creeping was performed, by dedicating one minute to each side and performing two repetitions in each session.

For the 1st phase of reflex rolling, the child is placed in dorsal decubitus, with the head turned to one side at an angle of 30°, the spine as aligned as possible, and the limbs relaxed. The physiotherapist applies gentle pressure with his thumb at the point of intersection of the mammillary line with the diaphragm, between the 6th–7th intercostal space, in the hemithorax and on the side towards which the head rotates, with a dorsal-medial-cranial direction, while resisting the turning of the head towards the other side with the other hand 18,19,21.

For reflex creeping, the child is placed proned, then passively bringing the head to axial neck extension and 30 degrees of rotation. The upper limb, on the side on which the head is turned, is placed in a position of shoulder flexion between 120 and 135 degrees, with 30 degrees of abduction, leaving the epitrochlea supported; the wrist is aligned with the shoulder, the forearm rests on the palmar face, and the longitudinal axis of the humerus points towards the vertex of the lumbosacral hinge. The opposite arm is placed relaxed and parallel to the longitudinal axis of the body.

The leg on the side toward which the child's head is turned is supported, extended and relaxed. The other leg is placed with the hip in external rotation and abduction, leaving the support on the internal condyle of the femur, the knee slightly flexed, and the heel aligned with the ischium. The stimulation is performed, with the index finger of one hand, on the lateral tuberosity of the calcaneus, in the ventral-cranial-medial direction of the leg opposite to the turn of the head, and with the index finger of the other hand, on the epitrochlea of the arm towards which the head is turned, in a dorsal-medial-cranial direction20,21.

All the treatments were applied by the same physiotherapist who had more than 5 years of experience, and the infants in the 3 groups were evaluated under the same conditions.


Bone mineralization data and anthropometric measurements of weight, height, and head circumference were collected.

To measure bone mineralization, the tibial speed of sound (Tibial-SOS) was recorded using a quantitative ultrasound device (QUS) (Sunlight Omnisense 7000)25,26,43. It was measured on the third lower part of the left tibia, by keeping the knee bent at a 90-degree angle. The measurement point was made perpendicular to the direction of the bone. Three to five consecutive measurements were made, and the average was calculated to determine the Tibial-SOS (m/s).

Although DXA is the gold standard for determining bone density in older children and adults, some challenges arise when using this method in preterm infants, including movement artefacts, difficulty scanning small and sick infants44, high cost22 and the cumulative radiation dose and the stress of transport to and restraint in the unit26. QUS techniques, otherwise applied to peripheral sites, are safe, radiation-free, easy to use, portable and cost effective. These characteristics make them favourable for use in assessing bone status in preterm infants25,26.

Moreover, the Tibial-SOS provides information on bone mineralization and density, elasticity, cortical thickness, and bone microarchitecture25. In addition, its efficacy in evaluating the state of bones in preterm infants has been demonstrated26, and this, in addition to its high reproducibility and its non-invasive properties43, makes it an ideal instrument for our purposes.

Measurements of weight, height and head circumference were also collected. Body weight was measured by placing the baby naked on a digital scale (SECA), the height was measured as the distance from head to heel with a non-elastic tape, and head circumference was measured at its widest part between the eyebrows and the occiput, also using a non-elastic tape.

Tibial SOS measurements were performed three times by a neonatologist: one day before starting treatment sessions, after two weeks of treatment and at the end of treatment. Inter-rater reliability and intra-rater reliability were high, with intraclass correlation coefficients (ICCs) of 0.852 and 0.861, respectively.

Anthropometric measures were taken from one day before starting the treatment to one day after finishing it, and collecting them on alternating days, according to the nursing protocol, and they were performed by staff. For our analysis, we used those that coincided with the day the Tibial-SOS was measured, or, failing that, the last measurement made before that day.

The Z score was calculated for birth weight and for weight, height and head circumference at the different measurement moments, following the 2013 Fenton growth charts for this purpose45.

Sample size calculation

The sample size was determined by considering a 5% significance level, 80% statistical power and a high magnitude effect size according to Cohen’s criteria46. The software program nQuery Advisor version 7.046,47 gave us a previous sample size of 66 preterm infants (22 for each study group). However, due to sepsis that affected the hospital's neonatal intensive care unit (NICU), this unit was forced to close. No more patients were being admitted, and the studies that were in progress had to be postponed. This situation caused us to reach the scheduled end date, so the study had to be finished. Therefore, the total sample size was 46 new-borns distributed over the three study groups. The statistical analysis was performed with 70% of the total sample size, and a significant difference was observed in relation to the studied intervention.


The groups were formed by simple randomization. The randomization procedure consisted of sealed envelope labels containing a number for each group. A non-researcher drew a random number from the envelope each time a new patient was proposed for treatment and made the assignment. For ethical reasons, twins and triplets were assigned to the same group with the same number.


All the personnel who performed the measurement tests were external to the study and were blinded to which intervention group the patients belonged. Likewise, participants, family, and data analysts were also blinded. The physiotherapist who performed the treatments was blinded to the objectives of the study.

Statistical methods

The qualitative baseline sex characteristics of the infants were compared using a crosstab, and a Chi-square test was performed for its analysis. The quantitative variables (gestational age, birth weight, birth weight Z score, gestational age at baseline, weight, height, head circumference, anthropometric Z scores, and Tibial-SOS at baseline) were analysed by one-way analysis of variance. A mixed repeated measures analysis of variance was performed to compare the effect of the intervention on anthropometric and Tibial-SOS measures and on anthropometric Z scores, using the time of measurement as the intra-subject factor and the treatment group as the inter-subject factor. For cases in which the homoscedasticity assumption was not met, a robust mixed repeated measures analysis of variance was performed.
The 95% confidence intervals (95% CI) were adjusted by Bonferroni. A statistical analysis with intention to treat was performed for all variables using SPSS (Statistical Package for the Social Sciences) for Windows (v.22.0)48. The statistical significance was stipulated with p < 0.05. For the effect size, the eta square (η2) was calculated, considering a value of > 0.14 as high; moderate with values between 0.14 and 0.06; and small values between 0.06 and 0.0146,49,50. The data are presented as the means ± standard deviation.

Ethics approval and consent to participate

The study was approved by the HUCVA ethical committee for clinical research. Reference number: 07/15.

Informed consent

Informed consent was obtained from all subjects and/or their legal guardian(s).

Consent for publication

Not applicable.


Trial registered at First posted date 22/04/2020. Registration number: NCT04356807. URL:

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