The effect of anticipatory anxiety on gait kinematics

It is known that fear responses following threat encounter can inhibit motion, slowing down gait and inducing postural freezing. Nonetheless, it is less clear how anxiety due to threat anticipation impacts gait parameters. In the present work, we used a threat of scream paradigm to study the effects of anticipatory anxiety on gait. Our sample included 25 participants (15 female, aged 23.4 ± 1.8) who were instructed to walk on a walking track, while motion was recorded in 3D, via a VICON system. Ten trials were included in each of four alternating blocks, two “threat” and two “safe” blocks, 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. 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, anxiety increases from safe to threat were correlated to increased stride speed and length, decreased stride time and reduced stance phase duration. Increases in anxiety from safe to threat blocks also correlated with greater amplitude of the arm/leg swing, an effect fully mediated by increased stride speed. Overall, these results indicate that in healthy subjects anticipatory anxiety invigorates motion, by increasing speed. These results are discussed in term of the recent advancements in the understanding of defensive behavior, its neural correlates and on the possible clinical implications with regard to pathological anxiety.