Age-related differences in the effect of mental fatigue on obstacle crossing in virtual reality

In Japan, falls are the most common type of occupational accident, with inattention being one of its primary causes. Both mental fatigue and aging contribute to inattention and decline in physical performance; however, how these factors interact to affect physical performance is not fully understood. This study compared the effects of mental fatigue on physical movements between younger (aged 25-34 years) and middle-aged adults (aged 55-64 years) and examined age-specific fall risks. A total of 34 participants rated their fatigue using the visual analog scale, performed the psychomotor vigilance task as a measure of sustained attention, and completed an obstacle-crossing task in a virtual reality environment to measure toe clearance and swing time. Results showed that mental fatigue increased fall risk across all ages, with age-specific contributing factors. For middle-aged adults, reduced balance control and lower sensitivity to fatigue heightened fall risk. Meanwhile, in younger adults, mental fatigue combined with energy-efficient strategies raised fall risk. These findings highlight unique age-related risk factors exacerbated by mental fatigue, underscoring the importance of early guidance and education before middle age.