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Vieira da Fonseca M.1, de Souza Oliveira A.L.2, Luiz Carregaro R.3, Martins de Toledo A.3
1SARAH Rehabilitation Hospital Network/ Universidade de Brasília, College of Physical Education, Brasília, Brazil, 2Universidade de Brasilia, College of Physical Education, Brasília, Brazil, 3Universidade de Brasilia, School of Physical Therapy, Brasília, Brazil
Background: The investigation of the influence of intrinsic restrictions in infant's abilities is fundamental. However, studies focusing on populations under risk for motor development such as low birth weight preterm infants, that analyzed the reaching behavior, are scarce. There are some indicatives that low birth weight preterm infants presents a slower movement, with more adjustments and less rectilinear trajectory than full-term ones. Additionally, information of muscle's activation during reaching in this population is a valuable tool to elucidate the influence of low birth weight. To the best of our knowledge, this is the first study that investigated the electromyographic responses during the reaching of low birth weight preterm infants.
Purpose: The aim was to compare the muscle activation between fullterm infants with adequate weight and preterm infants with low birth weight during the reaching behavior.
Methods: Infants were evaluated at 6 months, and assigned to two groups: a) Low Birth Weight Group (LBW; 23 preterm infants, gestational age from 32 to 36 weeks and 6 days and born weighting less than 2500g); b) Appropriate Birth Weight Group (ABW; 35 fullterm infants, gestational age from 38 and 42 weeks and born weighting more than 2500g). Data were collected by a Trigno Wireless System (Delsys Inc.). The electrodes were positioned on the muscle belly of the Biceps Brachii, Triceps Brachii, Deltoid and Pectoralis Major. Infants were positioned in a chair with 50º of inclination and the object was showed by the examiner during 2 minutes in the middle line, at shoulder height, and arm length, moved momentarily, so that the infant could notice and try reaching. After reaching, the object was removed and showed again, to elicit a new reaching movement. The following variables were calculated: a) Muscle Activation - electromyographic signal amplitude of the muscles (Root Mean Square); b) Coactivation - Agonist / antagonist ratio between the Biceps RMS and Triceps RMS during the agonist phase of the Biceps. The Mann-Whitney U Test was used to compare groups. The significance level was set at 5% (P 0.05). The Institutional Ethics Committee granted approval (protocol n. 064/12).
Results: Muscle activation of the Biceps and Triceps were greater (P=0.031 and P=0.004, respectively) in the ABW compared to the LBW group. However, activation of the Deltoid and Trapezius and coactivation presented no significant differences between groups.
Conclusion(s): The low birth weight preterm infants presented lower muscle activation during reaching behavior, mainly related to the Biceps and Triceps, when compared to full-term infants. Future studies focusing on interventions and guidelines directed to low birth weight infants are warranted.
Implications: It is possible to assume that a reduced muscle mass and a decreased muscle tone in low birth weight infants influenced the muscle activation. Thus, the use of electromyography should be implemented in research that addresses the reaching behavior of infants.
Funding acknowledgements: The present study was supported by the CNPq (process n. 479202/2011-7)
Topic: Paediatrics
Ethics approval: The Institutional Ethics Committee of University of Brasilia granted approval (protocol n. 064/12).
All authors, affiliations and abstracts have been published as submitted.
