The effect of anxiety on gait: a threat-of-scream study.

It is known that fear responses to clearly identified threats can inhibit motion, slowing down gait and inducing postural freezing. Nonetheless, it is less clear how anxiety, which emerges during threat anticipation, affects gait parameters. In the present work, we used a threat-of-scream paradigm to study the effects of anxiety on gait. Twenty-five participants (15 female, aged 23.4 ± 1.8) were instructed to walk on a 5-m walking track, while motion was recorded in 3D, via a VICON system. Four alternating blocks, two "threat" and two "safe" blocks of 10 trials each, were signaled by colored stripes on a screen in front of the walking path. Participants were informed that they could hear a human scream in their headphones at any time during threat blocks, which were in fact always delivered during walking. On the contrary, no screams were delivered in the safe blocks. Results indicated that participants reported higher subjective anxiety during threat vs. safe blocks. Furthermore, increases in self-reported anxiety from safe to threat showed significant moderate correlations with increased stride speed and length, decreased stride time and decreased stance phase duration. Increases in anxiety were also moderately correlated with increased arm/leg swing amplitude, an effect that was fully mediated by increased stride speed. Overall, these results indicate that anxiety invigorates motion in healthy subjects, by increasing speed. These results are discussed in terms of the recent advancements in the understanding of defensive behavior, its neural correlates and on clinical implications relative to pathological anxiety.