Electronic Thesis and Dissertation Repository

Thesis Format



Master of Arts




Prapavessis, Harry


Mental fatigue negatively affects the productivity and health of the general population. Mental fatigue manifests following sustained mental activity and is defined by subjective feelings of inhibition and objective decrements in mental performance. Caffeine is one of the most common stimulants used to mitigate mental fatigue. However, regular caffeine consumption is associated with several side effects. The efficacy of acute aerobic exercise as an alternative mental fatigue intervention remains ambiguous. Thus, the present study compared 1) 20 minutes of moderate-intensity cycling, 2) consumption of 2.5 mg/kg of caffeine, and 3) placebo on objective (Psychomotor Vigilance Task) and subjective (visual analog scales) mental fatigue measures, following a 30-minute fatigue-induction task (Stroop task). Twenty-one caffeine consumers completed each aforementioned treatment. The accrual of mental fatigue was mitigated after caffeine consumption, but not acute exercise. Further investigations are warranted to determine the optimal dose of acute exercise for mitigating mental fatigue.

Summary for Lay Audience

Mental fatigue negatively affects our productivity and health. Mental fatigue occurs as a result of prolonged mental demands and is commonly recognized by feelings of weariness and a decline in mental performance. Apart from resting, the most common method individuals use to combat mental fatigue is caffeine consumption. Although caffeine consumption may reliably counteract mental fatigue, it is also associated with several unwanted side effects. Common side effects include withdrawal symptoms, such as headaches, anxiety, and muscle tremors. Therefore, new methods of mitigating mental fatigue with less side effects should be explored. A single bout of aerobic exercise (e.g., running and cycling) has been shown in the past to reliably improve cognitive functioning. In a similar way, exercise may be able to counteract mental fatigue. Currently, little is known about the ability of exercise to mitigate mental fatigue. Hence, the present study aimed to compare the effectiveness of 1) 20 minutes of moderate-intensity cycling, 2) consumption of 2.5 mg/kg of caffeine, and 3) placebo (i.e., corn starch powder that should have no effect on mental fatigue) in counteracting mental fatigue. We assessed participants’ objective performance on a mental fatigue-sensitive computerized test (i.e., 5-minute repeated reaction time test) and subjective ratings of mental fatigue, before and after a 30-minute mentally fatiguing task. To evaluate the effectiveness of exercise, caffeine, and placebo on mental fatigue, all treatments were completed prior to the mentally fatiguing task. Our findings showed that only consumption of 2.5 mg/kg of caffeine, not 20 minutes of moderate-intensity exercise, was effective in counteracting mental fatigue. Though exercise was not shown to be effective in the present study, these findings may lead to the development of more effective alternatives to caffeine consumption. Future research studies should focus on altering the intensity and duration of exercise to find the optimal ‘dose’ of exercise to counteract mental fatigue.

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