Human locomotion through a multiple obstacle environment: strategy changes as a result of visual field limitation

Abstract

This study investigated how human locomotion through an obstacle environment is influenced by visual field limitation. Participants were asked to walk at a comfortable pace to a target location while avoiding multiple vertical objects. During this task, they wore goggles restricting their visual field to small (S: 40°×25°), medium (M: 80°×60°), large (L: 115°×90°), or unlimited (U) visual field sizes. Full-body motion capture was used to extract for each trial the mean speed, pathlength, mean step width, magnitude of head rotation and head mean angular speed. The results show that compared with the U condition, the M and L conditions caused participants to select a wider path around the obstacles without slowing down or altering step width. However, the S condition did slow down the participants, and increased both their step width and path length. We conclude that only for the S condition, balancing problems were substantial enough to spend more energy associated with increased step width. In all cases, participants choose to optimize safety (collision avoidance) at the cost of spending more energy.

Fig. 1

Left image showing one of the visual field restricting goggles as well as the optical markers placed on a headband. Right MVN suit containing inertial sensory modules layout

Fig. 2

Dependent measures for a representative trial with dashed lines indicating walls. Left bold line represents the hip trajectory. From this, pathlength and mean speed were derived. Right black and white circles indicate right and left foot positions, respectively. Black line segments represent trunk orientation at each heel strike. Dotted lines indicate step length and width based on this orientation

Fig. 3

Pathlength of the hip as a function of visual field size: small (S: 40° × 25°), medium (M: 80° × 60°), large (L: 115° × 90°), and Unrestricted (U). The closest neighboring significantly different pairs are indicated by *(p < .05), **(p < .01) and ***(p < .001). Error bars represent standard error

Fig. 4

Mean walking speed over the interval between passing the first and last walls as a function of visual field size: Small (S: 40° × 25°), medium (M: 80° × 60°), large (L: 115° × 90°), and unrestricted (U). The closest neighboring significantly different pairs are indicated by *(p < .05), **(p < .01) and ***(p < .001). Error bars represent standard error

Fig. 5

Mean step width (proportional to leg length L) as a function of visual field size: small (S: 40° × 25°), medium (M: 80° × 60°), large (L: 115° × 90°), and unrestricted (U). The closest neighboring significantly different pairs are indicated by *(p < .05), **(p < .01) and ***(p < .001). Error bars represent standard error

Fig. 6

Head mean angular speed in the yaw (left panel) and pitch (right panel) direction as a function of visual field size: small (S: 40° × 25°), medium (M: 80° × 60°), large (L: 115° × 90°), and unrestricted (U). The closest neighboring significantly different pairs are indicated by *(p < .05), **(p < .01) and ***(p < .001). Error bars represent standard error