title: Infants born preterm exhibit different patterns of center-of-pressure movement than infants born at full term.
abstract: BACKGROUND
  Infants born preterm are at risk for developmental impairments related to postural control.
  
  
  OBJECTIVE
  The purpose of this study was to determine whether infants born preterm and infants born at full term differed in postural control at 1 to 3 weeks after term age.
  
  
  METHODS
  This study included 17 infants born preterm (mean gestational age=31.9 weeks, range=25.0-34.6) and 15 infants born at full term (mean gestational age=38.9 weeks, range=37.3-40.6). All infants were without diagnosed neurological or genetic conditions.
  
  
  METHODS
  Center-of-pressure (COP) data were recorded at 5 Hz while each infant was positioned supine on a pressure-sensitive mat in an alert behavioral state. Root mean square (RMS) displacement and approximate entropy (ApEn) were used to describe the COP movement variability in the time series. Differences between groups were identified using independent t tests.
  
  
  RESULTS
  The COP time series were found to be deterministic, suggesting order in the time series. Infants born preterm exhibited significantly larger RMS values in the caudal-cephalic direction than infants born at full term (1.11 and 0.83 cm, respectively; t=-2.6, df=30, P=.01). However, infants born at full term had significantly larger ApEn values in the caudal-cephalic direction (1.19 and 1.11, respectively; t=2.4, df=30, P=.02). The 2 groups did not differ in RMS or ApEn values in the medial-lateral direction or the resultant.
  
  
  CONCLUSIONS
  Infants born at full term exhibited COP displacements in the caudal-cephalic direction that were smaller in amplitude, but may be considered more complex or less predictable, than those of infants born preterm. One explanation is that infants born preterm exhibited more stereotypic patterns of movement, resulting in large, but repetitive, COP excursions. A combination of linear and nonlinear measures may provide insight into the control of posture of young infants.
authors.affiliation: Department of Physical Therapy, Virginia Commonwealth University, Richmond, VA 23298, USA. scdusing@vcu.edu
authors.forename: Stacey C
authors.initials: SC
authors.lastname: Dusing
authors.forename: Anastasia
authors.initials: A
authors.lastname: Kyvelidou
authors.forename: Vicki S
authors.initials: VS
authors.lastname: Mercer
authors.forename: Nick
authors.initials: N
authors.lastname: Stergiou
mesh_terms: D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D016683:Supine Position / Q000502:physiology; D047929:Term Birth / Q000502:physiology