Effects Of Moderate-Intensity Cycle Ergometer Exercise On Executive Function In Sedentary Undergraduates:Evidence From FNIRS

Objective:Sedentary behaviour damages the executive function,which affects academic performance and is critical to social-emotional development and physical and mental health.Regular exercises can improve executive function as well as prevent its decline,but the brain mechanisms behind remain unknown.This study will investigated the effects of 8 week moderate-intensity aerobic exercise on executive function and its brain mechanisms in sedentary undergraduate.Methods:In this study,44 sedentary undergraduates were selected and randomly divided into experimental group（n=20,M/F:12/8）and control group（n=19,M/F:10/9）.The experimental group performed moderate intensity pedaling power bicycle exercise.Maximum heart rate(HR_Max)=206.9-0.67×age,and moderate-intensity heart rate=HR_Max×（60%-70%）.The experiment lasted for eight weeks,five times a week 30 minutes one time,and eventually 39 subjects completed the experiment.Except for the exercise intervention,both groups kept their original daily habits.Each subject was tested before and after the intervention using E-Prime software to perform three tasks including:Stroop,2-back,and More-odd-shifting to assess inhibition,refresh,and conversion functions,to obtain accuracy（ACC）and reaction time（RT）.Hemodynamic changes in the prefrontal lobe were monitored simultaneously using a functional near-infrared spectroscopy（f NIRS）to obtain the change values of oxyhaemoglobin concentration（ΔHbO₂）.If in accordance with normal distribution,a two-way analysis of variance（ANOVA）with repeated measures was used.The Bonferroni method was used for multiple comparison corrections.Result:（1）Inhibitory function results:ACC,RT with a time and group interaction effect（ACC:P=0.020;RT:P=0.043）.The ACC was significantly higher post-intervention than pre-intervention in the experimental group（P=0.001）and also signific antly higher than in the control group post-intervention（P<0.001）.There was no significant difference in ACC pre-and pos-interventiont in the control group（P=0.805）.The RT was significantly lower Post-intervention than pre-intervention in the experimental group（P<0.001）and also significantly lower in the control group post-intervention（P=0.001）.There was no significant difference in RT pre-and post-intervention in the control group（P=0.102）.There was an interaction effect between time and group for ΔHbO₂ in channel 14（frontal pole area）,channel15（dorsolateral prefrontal cortex）and channel 22（ventrolateral prefrontal cortex）（channel 14:P=0.031;channel 15:P=0.030,channel 22:P=0.046）.ΔHbO₂ in channel 14（P=0.002）,channel 15（P=0.005）,and channel 22（P=0.019）were also significantly lower in the experimental group than in the control group post-intervention（channel 14:P=0.047;channel 15:P=0.019;channel 22:P=0.034）.There was no significant difference in the control group pre-and post-inter vention（channel 14:P=0.842;channel 15:P=0.819;channel 22:P=0.625）.（2）Refresh function results:ACC had no time and group interaction effect（P=0.193）.RT had a time and group interaction effect（P=0.005）.RT was signific antly lower in the experimental group post-intervention the intervention than pre-intervention（P<0.001）,but not significantly different in the control group on post-intervention（P=0.108）.There was no significant difference in RT pre-and post-in tervention in the control group（P=0.104）.ΔHbO₂ in Channel 5（frontal pole area）had time and group interaction effect（P=0.048）.ΔHbO₂ in Channel 5（P<0.001）decreased significantly post-intervention in the experimental group,but was not significantly different in the control group post-intervention（P=0.305）.There was no significant difference in the control group pre-and post-intervention（P=0.196）.（3）Conversion function results:ACC had no time and group interaction effect（P=0.462）.RT had a time and group interaction effect（P=0.016）.RT was significantly lower in the experimental group post（P=0.006）than pre-intervention（P=0.004）and also significantly lower than the control group post-intervention（P=0.004）.There was no significant difference in RT pre-and post-intervention in the co ntrol group（P=0.502）.There was an time and group interaction effect for ΔHbO₂ in channel 15（dorsolateral prefrontal cortex,P=0.013）and channel 22（ventrol ateral prefrontal cortex,P=0.047）.ΔHbO₂ decreased significantly in channel 15（P=0.001）and channel 22（P=0.005）post-intervention in the experimental group a nd was also significantly lower than in the control group post-intervention（chann el 15:P=0.044;channel 22:P=0.015）.There was no significant difference in the control group pre-and post-intervention（channel 15:P=0.833;channel 22:P=0.956）.Conclusion:8 weeks moderate-intensity aerobic exercise not only improves behavioural performance of executive function in sedentary undergraduate,but also reduces the prefrontal activation level during task performance,mainly in the frontal pole area,dorsolateral prefrontal cortex,and ventrolateral prefrontal cortex of the prefrontal cortex.