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Dynamic sitting in infants: Limits of stability

Jaya Rachwani1, Victor Santamaria2, Xupeng Ai3

  • 1Department of Physical Therapy, Hunter College, City University of New York, United States.

Gait & Posture
|April 13, 2023
PubMed

Insights

Infants reach farther forward than to the side when sitting. Leg movements help increase reach distance, while falling is more common during side reaches, especially for infants with lower motor scores.

Area of Science:

  • Developmental motor control
  • Infant biomechanics
  • Postural stability

Background:

  • Limits of stability (LOS) measure dynamic balance by assessing reach distances before loss of balance or base of support change.
  • Understanding LOS is crucial for evaluating infant motor development and identifying potential delays.

Purpose of the Study:

  • To quantify sitting stability limits in 6- to 10-month-old infants in forward and rightward directions.
  • To explore factors influencing these stability limits, such as age, motor skills, and movement strategies.

Main Methods:

  • Twenty-one infants (6-10 months) participated in a remote, video-recorded study.
  • Caregivers used a toy to encourage reaching until infants lost balance or adjusted their base of support.
  • 2D motion analysis (DeepLabCut) and behavioral coding (Datavyu) quantified trunk excursions and postural adjustments.

Main Results:

  • Infants demonstrated larger trunk excursions (indicating greater reach) in the forward direction compared to the rightward direction.
  • Trunk excursions correlated with sitting experience, and rightward excursions also correlated with Alberta Infant Motor Scale (AIMS) scores and age.
  • Infants with higher AIMS scores transitioned out of sitting, while those with lower scores sometimes fell, particularly during rightward reaches.
  • Increased use of leg movement strategies was associated with greater trunk excursion.

Conclusions:

  • Infants' sitting stability limits are direction-dependent, with greater reach capacity forward than laterally.
  • The development of sitting stability involves perceiving stability boundaries and adopting anticipatory postural strategies.
  • Interventions targeting sitting stability could benefit infants with or at risk of motor delays.
Abstract

Keywords:
InfantsLimits of stabilityPostural controlSitting

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