NEW PERSPECTIVES ON POSTURAL CONTROL IN CHILDREN AND ADULTS

Background: The main objective was to explore how the central nervous system (CNS) regulates the different neural mechanisms aimed at maintaining static and dynamic posture. The research activity RA-1 involved the postural analysis of children with neurological or neuromuscular diseases with the aim of differentiating the pathologies under study; the others (RA-2 and RA-3) focused on gait initiation (GI). Specifically, I started a study (RA-2) to assess the existence of Anticipatory Postural Adjustments (APAs) in healthy toddlers that could be relevant in anticipating the diagnosis of paediatric diseases. Finally, I looked at how APAs may change after fatigue (RA3-A) or following toe amputation (RA3-B) to understand what changes our CNS enacts according to circumstances and needs. Methods: Data in RA-1 and RA-3 were acquired using an optoelectronic system, dynamometric platforms and electromyographic probes while, in RA-2, data were obtained from a locomotion database collected at the Vrije Universiteit (VU) in Amsterdam. RA-1 involved twenty-five patients with clinical diagnosis of Duchenne Muscular Dystrophy (DMD), Charcot-Marie-Tooth disease (CMT), Hereditary Spastic Paraparesis (HSP) or Cerebral Palsy (CP), and twelve healthy children as a control group (HC). During static posturography, participants stood quietly for 30 s with their eyes open (EO) and closed (EC), while during dynamic assessment participants walked barefoot, choosing their speed. The RA-2 included seventeen children who performed "voluntary" GI. This analysis is stopped at data processing, pending the normalization data to be provided by VU. For RA-3, the participant stood on the force plate for 10 s and then start walking, at will. In RA3-A, sixteen healthy male adults and trained, wearing their sports shoes performed GI before and after one minute of uninterrupted countermovement jump. In RA3-B, a professional mountaineer whit all toes of his feet amputated performed GI barefoot and after wearing ad-hoc prosthetic shoes, which restored the foot original length. Results: In RA-1, static posturography revealed an imbalance in weight distribution between feet in DMDs compared to the HC, with a greater base of support. Instead, eye x pathology interaction showed a better performance of HSPs with EC than with EO. Moving to kinematics, the time courses of pelvic, spinal and trunk variables highlighted distinctive strategies adopted by groups. In RA3-A, the effect of fatigue reached significance in the Erector Spinae (ES) of the trailing side and in the Obliquus Abdominis of the leading while all muscles were significantly delayed in APA activity after fatigue. In RA3-B, when barefoot, ES showed reciprocal activity between body sides. When shod, ES were bilaterally inhibited. This different behaviour was accompanied respectively by a rotation toward the trailing side (“turning” strategy) and by a forward projection of scapular girdle and pelvis (“diving” strategy). Conclusions: This multivariate approach highlighted the idea that each movement can be associated with a range of postural commands, each adapted to a specific context. Indeed, different postural strategies have been identified not only because of pathology but also based on the different conditions in which the self-confidence seems to be the switch for the change of strategy.