Mood, gait biomechanics, and cognitive load: investigating the influence of cognitive demands on the mood-motor relationship in young adults

INTRODUCTION
Major depression affects approximately 13% of the global population and is a leading cause of disability [1]. Yet its impact extends beyond mood disturbances to include subtle motor impairments such as altered gait, slumped posture, and balance deficits [2]. Although these motor symptoms are often overlooked, emerging evidence suggests that affective processing and motor control are intricately linked, particularly under conditions of increased cognitive demand. This study aims to identify key biomechanical variables correlated with emotional processing and mood under both single-task and dual-task walking conditions in a non-clinical sample. This work is intended to inform future interventions that target both mood and motor function in individuals with major depression.

METHODS
Twenty-two young adults (age 19.6 ± 0.6 years) provided written informed consent and underwent baseline psychological assessments. Depressive symptoms were measured using the Patient Health Questionnaire (PHQ-8), anxiety with the Generalized Anxiety Disorder-7 (GAD-7) scale, and affective processing was evaluated using the CANTAB emotional bias task (recording the mean and standard deviation of reaction times for selecting “Sad”). Biomechanical data were collected using a dual-system approach. A Kistler force plate embedded in a 10-meter walkway recorded high-resolution (1000 Hz) force data to capture gait events—such as initial contact and toe-off—and extract variables including walking velocity, anterior-posterior and mediolateral forces, impulse, and force variability. In parallel, six Vicon Blue Trident IMUs were attached to the participants to record kinematic data throughout the six 10-meter walks; although these data will be processed and analysed at a later date, they are expected to provide valuable insights into segmental kinematics, and overall gait kinematics.

Participants completed six continuous 10-meter walks at a self-selected pace under two distinct conditions (Figure 1). In the single-task condition, participants walked without any additional cognitive challenge, thereby providing a baseline measure of natural gait mechanics. In the dual-task condition, participants performed the same walking task while simultaneously counting backwards by 3’s, thereby imposing an ecologically valid cognitive load. Key gait events were identified from the force plate's vertical force curve, and corresponding biomechanical variables were extracted. Subsequent correlation analyses were conducted to evaluate the relationships between the psychological measures and the biomechanical outputs across both walking conditions, allowing for a nuanced understanding of how affective processing interacts with motor control under varying cognitive demands.

Figure 1. Experimental set up

RESULTS & DISCUSSION
Under dual-task conditions, slower emotional processing of sad faces (longer reaction times) was significantly correlated with reduced mean walking velocity (r = –0.749, p < 0.001) and lower anterior-posterior force production (r = –0.516, p = 0.017), indicative of a cautious gait strategy when cognitive load increased. Moreover, mediolateral force variability was significantly negatively correlated with reaction time variability for both sad (r = –0.621, p = 0.003) and happy faces (r = –0.576, p = 0.006), suggesting that more consistent affective responses were associated with greater lateral force modulation. In contrast, during single-task walking, slower reaction times to sad faces were positively correlated with higher anterior-posterior (r = 0.45, p = 0.035) and mediolateral forces (r = 0.48, p = 0.023), while stance time variability showed significant negative correlations with both reaction time (r = –0.55, p = 0.008) and its variability (r = –0.45, p = 0.038). Minimal depressive symptoms were observed (PHQ-8 scores), which likely accounts for the absence of significant correlations between depressive symptom severity and biomechanical measures. These findings underscore the complex interplay between affective processing and gait biomechanics, suggesting that dual-task conditions may amplify latent motor control deficits. The contrasting results between single-task and dual-task conditions also imply that compensatory mechanisms may be at play when cognitive demands are minimal. These baseline findings provide valuable insights into the potential of gait measures as early indicators of mood disturbances, supporting further work to develop targeted biomechanical interventions for major depression.

CONCLUSION
Our findings reveal that cognitive load profoundly alters the relationship between affective processing and gait biomechanics. Under dual-task conditions, slower processing of emotional cues is linked to a cautious gait—manifested by reduced speed and force—while single-task walking suggests a compensatory increase in force production. These insights underscore the value of integrating cognitive and motor assessments to detect subtle mood disturbances. Ultimately, this study lays a robust foundation for developing targeted biomechanical interventions that could not only serve as early markers of depression but also improve mood and quality of life in affected individuals.