Recurrence quantification analysis of the effects of height-induced postural threat and arm movement restriction on balance performance in children and young adults

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Nonlinear methods such as recurrence quantification analysis (RQA) have been used to provide complementary information into the effects of height-induced postural threat, however, without considering age- and task-related aspects. Thus, RQA was applied to investigate the effects of height-induced postural threat and arm movement restriction on balance performance in children compared to adults. In Experiment 1, 49 participants (26 children, 23 young adults) performed the tandem stance, while 48 participants (25 children, 23 young adults) conducted the unipedal stance with contralateral leg swing in Experiment 2. In both studies, standing at ground-level (no threat) and 80 cm above ground (threat) was performed with both free and restricted arm positions. RQA was conducted on center of pressure data from two previously published studies. In both experiments, group-by-threat interactions were detected, with adults demonstrating decreases in RQA parameters (Experiment 1: %DET AP, ENT AP, %LAM AP; Experiment 2: TT AP) when standing at height but children showing no adjustments. However, restriction of arms did not change the observed patterns. Overall, RQA provided information about the temporal organization of COP dynamics (more variable, less predictable, less complex, more random, less discontinuous, and shorter periods of invariant movement patterns due to height) that complemented the previously reported linear measures.