An increase in prefrontal oxygenation at the start of voluntary cycling exercise was observed independently of exercise effort and muscle mass
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We have reported using near-infrared spectroscopy that an increase in prefrontal oxygenated-hemoglobin concentration (Oxy-Hb) at the start of cycling exercise has relation to central command, defined as a feedforward signal descending from higher brain centers. The final output of central command evokes the exercise effort-dependent cardiovascular responses. If the prefrontal cortex may output the final signal of central command toward the autonomic nervous system, the prefrontal oxygenation should increase depending on exercise effort. To test the hypothesis, we investigated the effects of exercise intensity and muscle mass on prefrontal oxygenation in 13 subjects.
The subjects performed one- or two-legged cycling at various relative intensities for 1 min. The prefrontal Oxy-Hb and cardiovascular variables were simultaneously measured during exercise.
The increase in cardiac output and the decrease in total peripheral resistance at the start of one- and two-legged cycling were augmented in proportion to exercise intensity and muscle mass recruitment. The prefrontal Oxy-Hb increased at the start of voluntary cycling, while such increase was not developed during passive cycling. Mental imagery of cycling also increased the prefrontal Oxy-Hb, concomitantly with peripheral muscle vasodilatation. However, the increase in prefrontal Oxy-Hb at the start of voluntary cycling seemed independent of exercise intensity and muscle mass recruitment.
It is likely that the increased prefrontal activity at the start of cycling exercise is not representative of the final output signal of central command itself toward the autonomic nervous system but may trigger neuronal activity in the caudal brain responsible for the generation of central command.
KeywordsCentral command Regional cerebral blood flow Exercise effort Near-infrared spectroscopy
Analysis of variance
Autonomic nervous system
Arterial blood pressure
Mean arterial blood pressure
Maximal voluntary exercise intensity
The midbrain periaqueductal gray area
Regional cerebral blood flow
The rating of perceived exertion
Total peripheral resistance
The midbrain ventral tegmental area
This study was funded by Grant-in-Aid (15H03061) for Scientific Research (B) from the Japan Society for the Promotion of Science (JSPS). R. A. was a Research Fellow supported by JSPS.
RA and KM: conception and design of research; RA, KE, NL, and KM performed experiments; RA analyzed data; RA and KM interpreted results of experiments; RA prepared figures; RA and KM drafted manuscript; RA, KE, NL, and KM edited and revised manuscript; RA, KE, NL, and KM approved the final version of manuscript and had responsibility for all aspects of the work.
Compliance with ethical standards
Conflict of interest
All authors declare that they have no conflict of interest with regard to this study.
All procedures and protocols performed in this study were in accordance with the ethical standards by the Physiological Society of Japan and with the 1964 Helsinki declaration and its later amendments and were approved by the Institutional Ethical Committee of Hiroshima University (permit no. E-532). Informed written consent was obtained from all participants included in this study.
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