Discussion
OBESE
In the 12-week double-blinded RCT study, we investigated the effect of HIIT and MICT on executive function in young adults and explored the potential underlying mechanism of exercise on cognitive performance through CB. Our findings revealed that cognitive performance improved significantly in both the HIIT and MICT groups, with MICT showing greater benefits. These results suggest that even in young adults with peak cognitive ability, exercise, especially MICT, can enhance executive function. We also observed a significant improvement in CBF, as evidenced by increased PI, RI, and S/D, in the MICT group after the 12-week intervention. Furthermore, we identified a significant association between CBF and executive function, suggesting that CBF may represent a potential mechanism through which exercise enhances executive function.After a 12-week intervention, we observed a significant improvement in executive function among both the HIIT and MICT groups in young adults, with MICT demonstrating greater benefits. These findings are consistent with a previous study that investigated the effects of 12 weeks of combined aerobic and resistance exercise on neurocognitive performance in obese women. The study reported improvements in physical fitness, weight status, and cognitive interference inhibition following the interventionWe sought to explore whether different exercise modalities (MICT and HIIT) had comparable effects on enhancing executive function in young adults. Our results demonstrated that the MICT intervention was more effective than HIIT after 12 weeks of interventions. This finding is consistent with a previous article, which reported that aerobic exercise, such as MICT, can create a nutritive environment in the brain by facilitating cortical activity, hemodynamics, and metabolismFollowing the 12-week intervention, statistically significant differences were observed in PI, RI, and S/D of the CBF, particularly in MICT group. Research has demonstrated that changes in CBF are intensity-dependent, with CBF velocity in the MCA increasing linearly with exercise intensity until approximately 60–70% of maximal VOSeveral studies have reported the effect of exercise on cognitive function, often focusing on changes in brain activation and synaptic plasticity assessed using fMRI and EEG in humansSome limitations should be acknowledged in this study. Firstly, 12 weeks of intervention is relatively short for improving young adults’ CBF and executive function. Future studies with extended intervention periods are preferred to further explore the benefits. Secondly, our sample was small considering the methodological limitations, such as the challenges of CBF assessment with transcranial Doppler ultrasonography due to the thickness of the temporal bone, which even resulted in some participants from whom no signal could be acquired at all. However, all the CBF indexes were assessed by the same researcher and measured in a similar way during the whole process of the research. Additionally, we checked and confirmed data quality during preprocessing to ensure the measurement validity of CBF. Thirdly, the intermediary effect of CBF was not found, which may be due to the small sample size. We were able to identify a significant association between CBF and executive function. Thus, well-designed randomized controlled trials with larger sample sizes are needed to assess the effects of exercises on executive function and the mediation mechanism of CBF. Finally, the RCT study was conducted in a population of healthy young adults, so the study findings may not be generalizable to older people and clinical patients. However, this study also has notable strengths. First, to the best of our knowledge, this is the first double-blind RCT study that provides direct  evidence comparing the effects of MICT and HIIT interventions on executive function in young adults. Secondly, to determine the appropriate MICT and HIIT protocol, an individual’s maximal oxygen uptake was measured through a laboratory cardiopulmonary exercise test. This approach is considered more precise than other methods employed in previous studies. Most importantly, this randomized controlled trial study provides valuable insights into the causal effects of MICT/HIIT intervention on executive function. Moreover, the evidence will be necessary for understanding why exercise can improve executive function and further confirm the CBF mechanism of exercise on executive function. The results provided suggestions to young adults when choosing different modalities of exercise in real life to improve executive function and maintain brain health.