Brain drain: the impact of increased cognitive load on self-paced running performance

The brain is suggested to control pace selection throughout an exercise event in order to cover a pre-determined distance in the quickest time. The notion that the brain’s information processing capacity is limited, in addition to findings that during high to maximal exercise intensities cerebral blood flow declines to resting levels, implies the brain’s capacity to execute an optimal pacing strategy may be restricted. The purpose of this study was to evaluate the impact of additional cognitive load on pace selection during 5km running performance. Eleven participants (n=11; 23.8 ± 4.0yrs; 177.9 ± 5.9 cm; 75.0 ± 7.2 kg; 53.1 ± 2.7 ml/kg/min) completed 3 self-paced 5km runs on a non-motorised treadmill in a randomised order. This included a baseline 5km (CON), a 5km during a continuous Wisconsin Card Sorting Task (WCST-5km) and a 5km during a continuous Simplified Go/No-Go task (SGNG-5km). Electromyography (EMG) of the vastus lateralis, task effort awareness (TEA), physical-ratings of perceived exertion (P-RPE) and feeling scale (FS) were obtained every 0.5km. Finishing times between CON and SGNG-5km were non-significant (p = 0.18) whereas a significant difference was found between CON and WCST-5km (p<0.01); and between SGNG-5km and WCST-5km (p = 0.049). Participation in the WCST had a greater detrimental effect on 5km completion time 4.5% versus a 2.6% decrement during SGNG participation. Mean % EMG of MVC was significantly different (p <0.01) between all trials. Mean P-RPE was significantly different between CON and 5km-WCST (p = 0.05) and between 5km-SGNG and 5km-WCST (p<0.01). TEA was significantly different from CON to 5km-SGNG (p = 0.03) and 5km-WCST (p<0.01). FS during 5km-WCST was significantly different from CON (p<0.01) and 5km-SGNG (p = 0.04). Percentage correct responses scored on a baseline SGNG, were not significantly different from 5km-SGNG, (p = 0.06). Percentage correct responses scored were significantly reduced during 5km-WCST (p<0.01) compared to baseline WCST. In conclusion, additional cognitive load during 5km running negatively affects performance. In addition, brain areas associated with performance in WCST such as the pre-frontal regions may have a mediating role of pace regulation during 5km running performance.