2026-10-062026-10-062026SOUZA, Luciane Gisele Olimpio de. Maturação do controle segmentar de tronco e do equilíbrio reativo em lactentes sentados : análise acelerométrica. Orientadora : Lucieny da Silva Pontes. 2026. 77 f. Dissertação ( Mestrado em Reabilitação e Desempenho Funcional) - Centro de Ciências Biológicas e da Saúde, Universidade do Estado do Pará, Belém, 2026.https://portaldaposgraduacao.uepa.br/handle/riuepa/320AbertoDesenvolvimento MotorEquilíbrio posturalLactenteEquilíbrio (fisiologia)Motor developmentPostural balanceInfantBalance (Physiology)DissertaçãoCiências BiológicasPostural control develops progressively and nonlinearly, depending on the multisystem integration of sensory inputs, muscular responses, and anticipatory adjustments. The acquisition of independent sitting is a critical motor milestone for the development of subsequent motor skills, such as fine motor coordination and walking. Despite their widespread use in clinical practice and research, conventional motor assessment scales have limitations in detecting subtle deficits in trunk postural control during sitting, particularly in at-risk populations. Advances in portable technologies and the incorporation of inertial sensors have expanded access to the assessment of human movement disorders, enabling more objective measurement of kinematic variables related to postural control, particularly in infants, and representing a promising alternative for improving diagnostic accuracy and supporting evidence-based clinical decisionmaking. Objective: To analyze and compare the response time of reactive motor responses during sitting in response to standardized external perturbations in typically developing, full-term infants, using accelerometry across different age groups. Methods: This was an observational, crosssectional analytical study involving 28 infants, divided into two age groups: G1, 4–6 months (n = 14), and G2, 7–9 months (n = 14). Reactive response time to controlled external perturbations during sitting was analyzed according to movement type (passive and reactive), body segment (axillary and pelvic), and direction (left and right). Displacement time was assessed using an inertial sensor coupled to a smartphone. Statistical analyses included paired and independent samples t-tests, as well as mixed-design analysis of variance (ANOVA), with a significance level of 5% and effect size estimation using partial eta squared (η²p). Results: In G1, reactive responses were faster than passive responses and occurred exclusively at the pelvic segment, whereas in G2, reactive responses were also observed at the axillary segment, suggesting progressive maturation of postural control. Multivariate analysis demonstrated a significant influence of movement type, body segment, and laterality on response times, with the greatest effect observed for body segment (η²p = 0.115). Conclusion: Postural control in infants aged 4–9 months is rogressive, segmental, and asymmetric, and reactive response times appear to differ according to the axillary and pelvic segments analyzed. The combination of observational scales and smartphone-based accelerometry proved to be a valid and accessible approach for quantifying reactive trunk control, potentially contributing to the early screening of motor delays. The main limitations were the small sample size and the lack of objective measurement of the force applied during perturbations.PPGREAB - Avaliação e intervenção terapêutica nos sistemas neuromuscular