Comparison of Muscle O2 Dynamics at Different Sites of the Forearm Flexor Muscles During Incremental Handgrip Exercise
This study investigated heterogeneity of muscle O2 consumption (diffusive m-VO2) and muscle oxygenation difference (m-O2 difference) within the forearm flexor muscles using multi-optical fibers near-infrared continuous wave spectroscopy (NIRcws) during incremental exercise. Nine healthy male subjects performed incremental dynamic handgrip exercise until exhaustion. The workload was increased by 5% maximal voluntary contraction (MVC) every 1 min, starting at 10% MVC. The NIRcws probes (10 channels) were placed on the right forearm flexor muscles to monitor muscle oxygenation. The diffusive m-VO2 and the m-O2 difference were evaluated at each exercise stage. The diffusive m-VO2 at the medial site was significantly greater than the lateral site at 25% MVC (p < 0.05). Similarly, m-O2 difference at the medial site increased significantly over the lateral site (p < 0.05), whereas there were no significant differences in diffusive m-VO2 or m-O2 difference between the proximal and distal sites. These results in forearm muscle were different from the previous study which found that there were longitudinal differences in muscle VO2 in the femoral muscle.
The authors thank Christa Colletti for her help in writing the English manuscript. We also thank Mikiko Yonemitsu and Ayaka Sato for their helpful technical assistance. This work was supported in part by a grant-in-aid for scientific research from the Ministry of Education, Science, and Culture of Japan (No.18207019 to S. Koga), and a grant-in-aid for Young Scientists from the Japan Society for Promotion of Science (No. 18700536 to R. Kime).
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