| Purpose:This study aim to probe the characteristics of central fatigue during exercise with the investigation and analysis of the change in brain function of subjects in fatigue and in exhaustion by f-MRIMethods:In this study,11male athletes (20.27±0.79y, rV02max=60.05±3.30) were chosen according to the results of maximal oxygen uptake experiment and the performance of800-meter race. H1-MRS was utilized to analyze the proton spectrum in M1and basal ganglia of the subjects in resting state and the whole brain CBF and OEF of athletes were gained with ASL and ASE sequences. Meanwhile, BOLD-fMRI was also carried out to scan the brain of participants in resting state. In fatigue exercise, subjects were asked to drive the ergo bicycle with an initial load of90W and30W increment every2minutes till fatigue exists. Another one were required to do the power cycling at the intensity of VT and the speed of60±5r/min till exhaustion. MRI scans as mentioned above were utilized immedietlly.Results:1. After exercise-induced fatigue happened, the Cho/Cr in the left basal ganglia of subjects decreased from1.14±0.50to0.69±0.51(P<0.05), after the exercise-induced exhaustion existed, the NAA/Cr in the left M1increased from1.79±0.81to2.78±1.82(P<0.01).2. The whole brain CBF dropped from58.05±7.91ml/100g/min to52.30±7.30ml/100g/min(p<0.01) in addition to the falling of rCBF in right inferior frontal gyrus, left middle temporal gyrus, left and right striatum (P<0.01) while there is no change in OEF in the fatigue state. On the other hand, the whole brain CBF went down from58.05±7.91(ml/100g/min) in resting state to53.51±6.38(ml/100g/min) and the CBF of Right inferior frontal gyrus and ventral of left anterior cingulate also reduced (P<0.01) while on changes of OEF happened (p>0.05) in the exhaustion state after moderate-intensity exercise.3. Compared to resting state, the functional connectivity between M1and SMC and Cerebellum, hippocampus/parahippocampal and cerebellar network brain regions weakened after fatigue while the functional connectivity between somatosensory motor area and cerebellum, parahippocampal gyrus and cerebellum, frontal lobe and cerebellar network brain regions became weak after exhaustion.Conclusions:Based on the results above, it could be found that1. The increment of NAA/Cr in both side of the basal ganglia and Cho/Cr in the left Ml is the restricting factor of exercise-induced pump while the ascent of Cho/Cr in the right M1and Cho/Cr in the left basal ganglia is the constraints of exercise-induced fatigue;2. The drop of CMRO2, which is caused by the decrement of rCBF in right inferior frontal gyrus, left middle temporal gyrus and left and right striatum accompanied with the stability of OEF, is one of central influences on exercise-induced fatigue. Meanwhile, the drop of CMRO2, which is caused by the decrement of CBF in right inferior frontal gyrus and the ventral of left anterior cingulate accompanied with the stability of OEF, is one of central influences on exercise-induced exhaustion.3. In the resting state, the cerebellum is the center of all the default network of brain regions of athletes, which forms a steady network system, of which the functional connectivity drops in the fatigue or exhaustion states.
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