The competition between brain and body: Does performing simultaneous cognitive and physical tasks alter the cortical...

The underlying mechanism of an acute trade-off between cognitive and physical performances in athletes is still unclear. This study examined the effect of simultaneous cognitive and physical tasks on cortical electrical activity in 13 well-trained individuals who completed the "isolated" cognitive task (Stroop task), "isolated" physical task (12-minute cycle ergometer task), and the simultaneous (Stroop task + cycle ergometer) conditions. The participants fulfilled the subjective workload scale (NASA-TLX) and the ratings of perceived effort scale. For the cortical activity analysis (EEG), data from seven participants were retained allowing the analysis of 434 observational units for each condition. Spectral power was calculated for delta δ (0.5 to ≤4 Hz), theta θ (>4 to ≤8 Hz), alpha α (>8 to ≤13 Hz), beta β (>13 to ≤30 Hz) and gamma γ (>30 Hz) frequencies, and the biomarker theta-beta ratio (TBR). Significantly lower activity in gamma, beta and alpha bands during the isolated physical task and simultaneous condition (vs. cognitive condition) was observed (p < 0.001). Moreover, the relative slow frequencies were higher during the isolated physical task and simultaneous conditions, with higher predominance during the simultaneous condition (p < 0.001). The TBR presented a higher value for simultaneous (vs. isolated physical and isolated cognitive), with a higher value for the physical compared to cognitive condition (p < 0.001). This shift suggests that when the brain is concurrently managing cognitive load and physical effort, there is a redistribution of oscillatory activity, possibly reflecting a more energy-conserving or integrative cortical state.