Effects of Cognitive Fatigue on Gait

Background:

Most prior research on mental fatigue and gait has examined concurrent dual-task walking, in which a cognitive task and walking occur simultaneously. It remains unclear whether gait is altered following (rather than during) a mentally fatiguing task. This study addresses that gap using TloadDback, an adaptive N-back paradigm (Borragán et al., 2016) that individually calibrates cognitive demand to maintain consistent task difficulty across participants, as the mental fatigue induction method.

Design:

This is a within-subject, repeated-measures design. All primary analyses will be conducted on data collected during the in-person session. Sample size (up to 30 enrolled, target N = 24) was determined via a power analysis using pilot data (N = 5; within-subject design, α = 0.05, power = 0.90).

Mental Fatigue Induction Task:

TloadDback is administered as a single continuous 32-minute block. Participants view a continuous sequence of number-letter-number stimuli and respond via keypress (odd/even number), when seeing a number, or spacebar (letter repeat), when seeing a letter. Stimulus-presentation speed is individually calibrated during the practice session to the maximum speed at which the participant maintains greater than 85% accuracy, ensuring standardized cognitive demand across participants during the main session.

Sensor:

Inertial measurement units (IMUs): 8 units, placed at the shanks (2), thighs (2), feet (2), upper spine (1), and lower back (1), capturing spatiotemporal and kinematic gait parameters.

Pressure-sensing insoles: worn inside participants' shoes to detect gait events (heel strike, toe-off), complementing IMU-derived timing data.

Eye tracker: recording pupil diameter, blink rate, and fixation duration.

EEG cap: records brain's electrical voltage fluctuaction to obtain metrics such as frequency band analysis and neural signals related.

IMUs and insoles are used primarily to obtain gait parameters, whereas eye tracking and EEG are used only during the mental fatigue-inducing computer task, serving as physiological metrics to corroborate fatigue.

Procedures

Practice session (remote, online via PsychoPy/Pavlovia): Participants complete a familiarization run of TloadDback for individual speed calibration

In-person session pipeline:

Demographic questionnaire. Sensor placement: IMUs and insoles Baseline gait trial (10-meter straight-line walk). A 3-minute Psychomotor Vigilance Task (PVT), in which participants respond as quickly as possible by pressing the spacebar each time a visual stimulus (a dot) appears at random inter-stimulus intervals.

Sensor placement: Eye tracker and EEG. TloadDback task (32 minutes continuous). Repeat the 3-minute Psychomotor Vigilance Task (PVT). Take off the Eye Tracker and EEG. Post-task gait and recovery assessment: repeated cycles of a straight-line walk trial followed by a 3-minute rest, for a total of 4 post-task walk assessments.

Visual Analog Scale (VAS) ratings (fatigue, boredom) are collected at multiple points across the session to track the time course of fatigue and alertness.