From Neural Command to Robotic Use: The Role of Symmetry/Asymmetry in Postural and Locomotor Activities

Abstract

This article deepens a reflection on why and how symmetry/asymmetry affects the motor and postural behavior from the neural source, uterine development, child maturation, and how the notion of symmetry/asymmetry has been applied to walking robot design and control. The concepts of morphology and tensegrity are also presented to illustrate how the biological structures have been used in both sciences and arts. The development of the brain and the neuro-fascia-musculoskeletal system seems to be quite symmetric from the beginning of life through to complete maturity. The neural sources of movements (i.e., central pattern generators) are able to produce both symmetric or asymmetric responses to accommodate to environmental constraints and task requirements. Despite the fact that the human development is mainly symmetric, asymmetries already regulate neurological and physiological development. Laterality and sports training could affect natural musculoskeletal symmetry. The plasticity and flexibility of the nervous system allows the abilities to adapt and compensate for environmental constraints and musculoskeletal asymmetries in order to optimize the postural and movement control. For designing humanoid walking robots, symmetry approaches have been mainly used to reduce the complexity of the online calculation. Applications in neurological retraining and rehabilitation should also be considered.

Impacts of Developmental Coordination Disorder on Postural Control Mechanisms in Children and Early Adolescents

“…Similarly, in other voluntary dynamic postural tasks, the children with DCD have significant velocity and timing ML postural control deficits compared to their peers (Deconinck et al, 2010;Wilmut & Barnett, 2017). The body weight transfers (load/unload mechanism) that are required along the ML postural control (hip strategy) could be more demanding and more complex than the transfers required along the AP axis, in which balance is under ankle control (plantar/dorsiflexor) (Blanchet et al, 2019(Blanchet et al, , 2021bBlanchet & Prince, 2023;Winter et al, 1996). Several studies have shown that the difference between children with DCD and their peers increased with the complexity of postural tasks (Adams et al, 2014;INSERM, 2019;Verbecque et al, 2021;Wilson et al, 2013).…”

“…For example, the improvement in balance control with age is demonstrated mainly by the decrease in the amplitude of COP displacements (Hatzitaki et al, 2002;Rival et al, 2005;Schedler et al, 2019;Wolff et al, 1998), the frequency of postural oscillation (Figura et al, 1991;Riach & Starkes, 1994;Rival et al, 2005;Wolff et al, 1998), as well as increase limit of stability (Blanchet et al, 2019;Riach & Starkes, 1993) in a nonmonotonic development pattern (Assaiante, 2012;Blanchet et al, 2019;Kirshenbaum et al, 2001;Rival et al, 2005;Schedler et al, 2019). These developmental changes are fine-tuned by experience (Blanchet et al, 2019(Blanchet et al, , 2021bHadders-Algra, 2010). Moreover, the results of studies aimed at evaluating postural development skills appear to be dependent on the testing tools and experimental conditions employed, subjects' ages, as well as the specific balance skills examined (Franjoine et al, 2010;Haddad et al, 2013).…”

School Scoliosis Screening: The Influence of Dominant Limbs and Gender

“…Early specialization may also increase the risk of developing postural asymmetries, leading progressively to acute and/or chronic injuries in both boys [34,35,[37][38][39] and girls [40,41]. Furthermore, it has been suggested that, in young male and female athletes, laterality in certain sports could be related to asymmetrical bones and muscle circumference adaptations, which might also be correlated with muscle flexibility and strength [40][41][42]. However, more well-controlled studies are required to examine why cross laterality is more evident in boys than in girls.…”