Executive function during exercise is diminished by prolonged cognitive effort in men.

The speed and accuracy of decision-making (i.e., executive function (EF) domains) is an integral factor in many sports. At rest, prolonged cognitive load (pCL) impairs reaction time (RT). In contrast, exercise improves RT and EF. We hypothesized that RT and EF during exercise would be diminished by prolonged 'dual tasking' as a consequence of pCL. To test the hypothesis, twenty healthy male participants performed four conditions [resting control (Rest), pCL only (pCL), exercise only (EX), and pCL + exercise (pCL)] in a randomized-crossover design. Both exercise conditions utilized a 50-min cycling exercise protocol (60% VO peak) and the pCL was achieved via a 50-min colour-word Stroop task (CWST). Compared with Rest, pCL caused a slowed CWST RT (P < 0.05) and a large SD (i.e., intraindividual variability) of CWST RT (P < 0.01). Similarly, compared with EX, the slowed CWST RT (P < 0.05) and large SD of CWST RT (P < 0.01) were also observed in pCL. Whereas the reverse-Stroop interference was not affected in pCL (P = 0.46), it was larger (i.e., declined EF) in pCL than EX condition (P < 0.05). These observations provide evidence that the effort of pCL impairs RT and EF even during exercise.