Effects of restricted compared to free arms motion during standing and walking at height in healthy adolescents.

In adults, it is firmly established that height-induced postural threat as well as restriction of arms motion led to detrimental effects on emotional state and standing/walking outcomes. However, little is known about how both factors influence subjective and objective outcomes in adolescents where mechanisms to control standing and walking are still not adult-like. This work investigated emotional state and performance outcomes while standing and walking with free and restricted arms motion at ground level and at height. Twenty-five and 28 adolescents were recruited for study 1 (standing) and study 2 (walking), respectively. Participants stood (tandem stance) or walked (5 m at self-selected speed) with free or restricted arm position at both ground-level (no threat) and 80 cm above ground (threat). Postural sway (i.e., amplitude, frequency, sample entropy) and spatiotemporal gait (i.e., walking speed, time, steps, cadence) parameters were used as objective performance outcomes. Self-reported emotional state responses (i.e., balance confidence, fear of falling, perceived instability, conscious balance processing) were used as subjective indicators. In both studies, height-induced postural threat led to detrimental effects on emotional state and standing/walking outcomes. Further, adolescents in study 1 adopted a postural control strategy that differed from a "stiffening" response reported for young adults. In addition, threat-related deteriorations in spatiotemporal gait outcomes (study 2) were further amplified when arms were restricted. The findings replicate but also expand previous research about the effects of postural threat and restricted arms motion on emotional state and standing/walking outcomes and provide additional knowledge on how young people act under these conditions.