Does A Mentally Demanding Cognitive Task Influence Motor Reaction Time?

Abstract

PURPOSE: Recent research has reported mental fatigue not only impairs endurance, but also sport-specific technical performance. Therefore we sought to examine the effect of a mentally fatiguing task on a motor-reaction time (M-RT) task. METHODS: A M-RT task was developed with Fitlight-hardware and –software in order to evaluate the effect of mental fatigue on stimuli-type (simple vs. response inhibition) and visual-field position (central vs. peripheral). Eleven untrained healthy subjects (age: 25 ± 4y; 6 female, 5 male) performed two experimental trials in a randomized crossover order. Participants first completed a baseline M-RT task (~6min30sec), followed by a Flanker task. Next they performed either a 90min mentally fatiguing task (Stroop task; MF) or watched a 90min documentary (CON). Immediately thereafter again the Flanker task and the M-RT task were completed. Accuracy (ACC) and reaction time (RT) were followed up in all tasks but the documentary. In addition multiple physiological and psychological measures were assessed during the protocol. RESULTS: ACC on both the Stroop task (p=0.021) and the Flanker task (~3%; p=0.048) dropped over time in MF. Participants got faster over time on the Stroop task in MF (p≤0.004). RT on the Flanker task did not change over time in both MF and CON. Subjectively, higher (p=0.001) mental fatigue was perceived in MF compared to CON. Concerning the M-RT-performance, no effects were observed for the simple stimuli. For the response inhibition-stimuli, only in MF participants became significantly slower in time (~7.5%; p=0.007). CONCLUSION: Mental fatigue negatively affects sport-specific response inhibition-RT. Therefore, besides endurance capacity, also sport-specific cognition appears to be impaired by mental fatigue. The impairment in RT was independent from the visual-field position of the stimulus and was not perceived by the participants.