The Impact of Mental Fatigue on a Strength Endurance Task: Is there a Role for the Movement-Related Cortical Potential?

PURPOSE: Several mechanisms have been proposed to explain how mental fatigue degrades sport performance. In terms of endurance performance, a role for an increased perceived exertion has been demonstrated. Utilizing electroencephalography (EEG) and, more specifically, the movement-related cortical potential (MRCP), the present study explored the neural mechanisms that could underly the mental fatigue-associated increase in perceived exertion.

METHODS: Fourteen participants (age: 23 ± 2 y, 5 females, 9 males) performed one familiarisation and two experimental trials in a randomised, blinded, cross-over study design. Participants had to complete a submaximal leg extension task after a mentally fatiguing task (EXP; individualized 60-min Stroop task) or control task (CON; documentary). The leg extension task consisted of performing 100 extensions at 35% of 1RM, during which multiple physiological (heart rate, EEG, ratings of perceived exertion) and psychological measures (self-reported feeling of mental fatigue, cognitive load, motivation) were assessed.

RESULTS: Self-reported feeling of mental fatigue was higher in EXP (72 ± 18) compared to CON (37 ± 17; p < 0.001). A decrease in flanker accuracy was detected only in EXP (from 0.96 ± 0.03 to 0.94 ± 0.03; p < 0.05). No significant differences between conditions were found in MRCP characteristics and perceived exertion. Specifically in EXP, alpha wave power increased during the leg extension task (p < 0.01).

CONCLUSIONS: Mental fatigue did not impact the perceived exertion or MRCP characteristics during the leg extension task. This could be related to low perceived exertion and/or the absence of a performance outcome during the leg extension task. The increase in alpha power during the leg extension task in EXP, suggests participants may engage a focused internal attention mechanism to maintain performance and mitigate feelings of fatigue.