Muscle oxygenation heterogeneity in a single muscle at rest and during bicycle exercise
We evaluated regional differences of muscle O2 dynamics between distal and proximal sites in the vastus lateralis (VL) muscle using near infrared spatial resolved spectroscopy (NIRSRS). forty-one male subjects performed a 30 W ramp incremental bicycle exercise test until exhaustion. The NIRSRS probes were attached on each distal and proximal site in the VL. The pulmonary O2 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 V̇O2max 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 V̇O2max may be due to enhanced O2 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 O2 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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