The effect of muscle metaboreflex on the distribution of blood flow in cerebral arteries during isometric exercise
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The present study examined the effect of muscle metaboreflex on blood flow in different cerebral arteries. Eleven healthy participants performed isometric, one-leg knee extension at 30% maximal voluntary contraction for 2 min. Activated muscle metaboreflex was isolated for 2 min by post-exercise muscle ischemia (PEMI). The contralateral internal carotid (ICA), vertebral (VA), and ipsilateral external carotid arteries (ECA) blood flows were evaluated using Doppler ultrasound. The ICA blood flow increased at the beginning of exercise (P = 0.004) but returned to the baseline level at the end of exercise (P = 0.055). In contrast, the VA blood flow increased and it was maintained until the end of the exercise (P = 0.011), while the ECA blood flow gradually increased throughout the exercise (P = 0.001). These findings indicate that isometric exercise causes a heterogeneous cerebral blood flow response in different cerebral arteries. During PEMI, the conductance of the VA as well as that of the ICA was significantly lower compared with the baseline value (P = 0.020 and P = 0.032, at PEMI90), while the conductance of the ECA was not different from the baseline (P = 0.587), suggesting that the posterior and anterior cerebral vasculature were similarly affected during exercise by activation of muscle metaboreceptors, but not in the non-cerebral artery. Since ECA branches from ICA, the balance in the different influence of muscle metaboreflex on ECA (vasodilation via exercise-induced hypertension) and ICA (vasoconstriction) may contribute to the decrease in ICA blood flow at the end of isometric exercise.
KeywordsInternal carotid artery External carotid artery Vertebral artery Cerebral blood flow Post-exercise muscle ischemia Exercise pressor reflex Central command
We appreciate the commitment of the study participants, the staff at the Research Institute of Physical Fitness, Japan Women’s College of Physical Education, and S. Ono and H. Sasaki for technical assistance. This study was supported, in part, by a Grant-in-Aid for Scientific Research from the Japanese Ministry of Education, Culture, Sports, Science and Technology 15H003098 (to S. Ogoh).
SO and KS were responsible for the conception and design of the research; SO, AH, and KS performed the experiments; SO, AH, and KS analyzed the data; SO and KS interpreted the results of the experiments; SO and KS prepared the figures; SO drafted the manuscript; all authors edited and revised the manuscript; all authors approved the final version of the manuscript.
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Conflict of interest
The authors declare that they have no conflict of interest.
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