Effects of the Additional Weight on the Reaching Behavior of Preterm Infants With Low Birth Weight: Randomized Controlled Trial

The effects of additional weight on early motor skills of infants have been increasingly studied. During the reaching behavior, the additional weight has been shown benefits in certain kinematic variables in full term and preterm infants. There is a growing interest in the study of populations at risk for motor development, especially considering interventions based on functional activities with the purpose of improving the neuromotor control, functional capacity and muscle strength. The aim of the present study is to investigate the effect of a functional training with additional weight in the reaching behavior of preterm infants with low birth weight and to compare the effects with a full term population. A controlled and randomized trial will be carried out with full term infants of adequate birth weight and preterm infants with low birth weight at 6 months of chronological or corrected age. The participants will be recruited by convenience from the charts of a Public Hospital. Participants will be randomly allocated into four groups: 1) adequate weight placebo group (AWPG); 2) adequate weight intervention group (AWIG); 2) low weight placebo group (LWPG) and 4) low weight intervention group (LWIG). . The assessor will be blinded (no knowledge of groups allocation). All infants will undergo a training program of eight sessions (2x/week; 4 weeks). The AWIG and LWIG will receive the training with an additional weight (characterized by a bracelet with a weight of 20% of the mass of the upper limbs)and the AWPG and LWPG will receive the same training, however, without the additional weight (only the bracelets).. All infants will be assessed in three different moments: 1) Pre-intervention: baseline, before the start of the intervention program; 2) Post-intervention: evaluation performed after the end of the program; and 3) Follow-up: evaluation performed seven days after the post-intervention assessment. The following kinematic dependent variables will be calculated: straightness index, mean velocity and motion units and electromyographic variables: pattern of activation and recruitment of muscle fibers - Biceps brachialis, Triceps brachialis, Deltoid and Pectoralis Major muscles; co-activation between biceps and triceps. The Qualisys Track Manager (QTM) and a wireless surface electromyography with 8-channels will be used. If normality assumptions are met, a mixed 2X2 ANOVA with repeated measures will be applied, in order to verify differences between the intervention programs, considering the dependent variables. Otherwise, non-parametric procedures of the same nature will be adopted. The significance will be set at 5% (P<0.05).