The present study examined the effects of acute CE and AE on inhibitory control, utilizing both behavioral and neuroelectric assessments among younger adults. We also investigated the mediating role of lactate in the relationship between acute exercise and inhibitory control. Our findings revealed that acute CE, combining both AE and RE, increased inhibitory control by reducing RT across all Stroop test conditions, regardless of accuracy. Beneficial effects for Stroop data were similar for acute AE. Differences in P3 amplitudes were observed only in the congruent condition, where the amplitudes of the CE group were significantly smaller than those of AE and CON groups. However, no mediating effects of lactate for acute exercise and inhibitory control were observed.
Relative to the hypothesis, our findings indicate that acute AE improved inhibitory control by reducing RT. These improvements were accompanied by no significant differences in accuracy, indicating that this enhancement is unlikely to be associated with a trade-off between speed and accuracy [56]. The results replicated previous studies demonstrating the positive effect of acute AE on inhibitory control among younger adults [57, 58]. A meta-analysis, synthesizing data from 55 effect sizes, also supports this, indicating a small and positive effect of acute moderate AE on inhibitory control (Hedges’ g = − 0.26, 95% CI: −0.34 to − 0.18) [59]. The design of acute AE in the present study, structured as a 25-minute moderate-intensity exercise, is noteworthy for its alignment with the PAGA recommendation regarding the facilitation of EF enhancements [12, 60]. Taken together, these findings suggest that acute AE, characterized by moderate intensity over a duration of 20 to 30 minutes, holds the potential to elicit a favorable effect on inhibitory control.
Similarly, our findings also indicate acute CE facilitated inhibitory control and this aligns with previous studies showing increased inhibitory control with acute CE [20, 21]. While Wen and Tsai [22] found no effect on inhibitory control after an interval-session of CE, the inconsistency may be attributed to the need for CE to incorporate both completing-sessions of AE and RE, if benefits on EFs are to be elicited [23]. Quintero, Bonilla-Vargas [61] tested CE that combined both AE with intensity interval form and RE and reported enhanced inhibitory control. This finding not only supports that a complete CE is essential for enhancing EFs but also supports the view that intensity interval forms of single AE, when integrated into a comprehensive CE session, could be also effective. Therefore, our findings extend previous research, emphasizing that the design of CE should include a completing-session of both AE and RE for optimal EFs benefits.
Contrary to our hypothesis, P3 amplitudes were not increased following AE. The inconsistency might be attributed to differences in cardiorespiratory fitness levels. For example, increased P3 amplitudes following acute AE were observed among individuals with higher cardiorespiratory fitness levels (49.18 ± 7.57 ml·kg− 1·min− 1) [62], whereas our participants demonstrated lower cardiorespiratory fitness levels (34.38 ± 4.84ml·kg− 1·min− 1). Tsai, Pan [63] compared acute AE effects on P3 amplitudes among younger adults with varying levels of cardiorespiratory fitness and indicated that the high-fitness group displayed larger P3 amplitudes compared to both the low-fitness and control groups, suggesting a potential association between cardiorespiratory fitness levels and differences in P3 amplitudes. A meta-analysis by Kao, Chen [28] supports this view and found the absence of a noticeable effect of acute exercise on P3 amplitudes in individuals with low cardiorespiratory fitness.
One of our novel findings is the reduction in P3 amplitudes observed following acute CE compared to acute AE and the control treatment, particularly noted in the congruent condition. The result was inconsistent with our hypothesis and might be attributed to cognitive demands [64]. Li, Karageorghis [23] found no difference in P3 amplitudes between acute CE and AE under high cognitive demands (i.e., cognitive flexibility) but observed larger P3 amplitudes for acute CE compared to the CON group, suggesting that acute CE might require increased attentional resources to meet higher cognitive demand conditions [27]. Contrary to expectations, our findings showed that in the congruent condition, which involves lower cognitive demands, acute CE triggered smaller P3 amplitudes compared to acute AE and the control treatment. This reduction in P3 amplitudes suggests a more efficient allocation of attentional resources during CE, possibly leading to enhanced inhibitory control. Taken together, our results suggest that following acute CE, attentional resources may be more efficiently managed, necessitating fewer resources particularly in conditions with lower cognitive demands. From a practical perspective, these data suggest that acute CE may help EF function in young adults. For instance, regular participation might mitigate interference during focused studying, and during demanding and critical work situations, CE might benefit transition and flexibly between different perspectives and ideas.
The findings of the present study indicated that lactate played no mediating role between acute exercise and inhibitory control. In contrast to our findings, Li, Karageorghis [23] showed that lactate mediated the impact of both acute AE and CE on EF, specifically cognitive flexibility. Cognitive flexibility necessitates concurrent engagement of both inhibitory control and working memory [64, 65], potentially imposing a greater cognitive demand compared to inhibitory control alone. Considering lactate might function as an energy source for the brain [31], it is plausible that the brain requires a lower amount of energy to support EFs with lower cognitive demand. Notably, both Li, Karageorghis [23] and our studies failed to observe the mediating role of lactate in the relationship between acute exercise and P3 amplitudes. Li, Karageorghis [23] proposed that the locus coeruleus-norepinephrine (LC-NE) system might serve as a possible mechanism between acute exercise and P3 amplitude. The LC serves as the supplier of NE, an important neurotransmitter for central nervous system function and behavior, to the hippocampus and cortex, influencing both cognitive and emotional processes [66]. Acute exercise leads to elevated cognitive performance and activation of the LC-NE system [67], suggesting that the LC-NE system might serve as a conceivable mechanism in the relationship between acute exercise and P3 amplitudes.
Our study has a number of strengths and is the first to examine the impact of acute CE on inhibitory control in younger adults, using a comprehensive set of measures that included both behavioral and neuroelectric assessments. We also explored the mediating influence of lactate on the relationship between acute exercise, inhibitory control, and P3 amplitudes, and aimed to elucidate the relationships among these factors. The study design was strong and incorporated a randomized between-group approach, encompassing both genders, and concurrently assessed cardiorespiratory and muscular fitness. This comprehensive approach allowed for the consideration of multiple factors, distinguishing our research from previous studies [20–22].
Several limitations should be acknowledged. Firstly, this study focused solely on the impact of CE on inhibitory control in an “aerobic-resistance order.” The effects of acute CE in the “resistance-aerobic order” on inhibitory control remain unexplored. Past research has shown that different sequences of acute CE can elicit distinct responses in growth hormones [68], which are associated with inhibitory control [69]. Secondly, this study inferred effects on inhibitory control, leaving the impact on working memory and planning, which are additional components, unexplored. Future studies should investigate the benefits of acute CE on working memory to explore both the similarities and differences across various core domains of EFs. This approach will provide a more comprehensive understanding of the positive effects of acute CE on EFs. Finally, it is important to note that, while we controlled for many factors, the ecological validity in practical settings still needs to be considered, such as the impact of exercise on work-related cognitive functions [70]. The transition from laboratory settings to real-world conditions is necessary.