Parameters of Surface Electromyograms in Full-Term and Preterm Infants in the Neonatal Period: The Possible Contribution of Gravity

The purpose of this study was to compare the postnatal evolution of spectral–amplitude and nonlinear parameters of surface electromyogram (sEMG) in the full-term and preterm infants with regard to their biological and calendar age. In full-term infants, all sEMG parameters (dimension, entropy, mean frequency, and amplitude) are increased by 10–30% two weeks after birth. On the contrary, sEMG parameters in preterm infants were constant for six weeks after birth. This finding indicates that both postnatal and antenatal periods are important for the development of the motor system of infants. Therefore, the adaptation of the motor system to extrauterine conditions consists of two stages. The authors suppose that gravity can be a driving factor of these sEMG metamorphoses.