Muscle oxygenation heterogeneity in a single muscle at rest and during bicycle exercise
We evaluated regional differences of muscle O 2 dynamics between distal and proximal sites in the vastus lateralis (VL) muscle using near infrared spatial resolved spectroscopy (NIR SRS). forty-one male subjects performed a 30 W ramp incremental bicycle exercise test until exhaustion. The NIR SRS probes were attached on each distal and proximal site in the VL. The pulmonary O 2 uptake and heart rate were monitored continuously during the experiment. The TOI at rest was significantly higher in proximal than distal sites (65.0±5.2 vs. 69.7±4.6%, p<0.001). The TOI at exhaustion was also significantly higher in proximal than distal sites (39.5±6.7 vs. 47.5 ±7.6%, p<0.00l). Moreover, a significant correlation was found between V̇O 2max and the TOI at exhaustion in each proximal and distal site in the VL. Half time reoxygenation, the time to reach a value of half-maximal recovery, was significantly slower in distal sites than proximal sites (27.1±5.6 vs. 25.0±6.1 sec, p<0.01). In conclusion, lower muscle oxygenation at exhaustion in higher V̇O 2max may be due to enhanced O 2 extraction in high oxidative capacity muscle. In addition, slower reoxygenation and lower muscle deoxygenation at the distal site in the VL may be explained by differences in O 2 supply and/or muscle fiber composition between distal and proximal sites.
Kime, R; Osada, T; Shiroishi, K; Ichimura, S; Kurosawa, Y; Homma, T; Nakagawa, N; Miyazaki, J; Murase, N; Katsumura, T
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