MUSCLE OXYGENATION HETEROGENEITY IN A SINGLE MUSCLE AT REST AND DURING BICYCLE EXERCISE / 体力科学

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 (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 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<0.001). Moreover, a significant correlation was found between VO₂max 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 VO₂max 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.

Differential digital plethysmographic analysis of microvascular response produced by the gravitational potential energy change / 体力科学

The effect of changes in vascular transmural pressure upon differential digital plethysmogram (delta DPG) was studied in seven normal subjects. Changes in vascular transmural pressure were produced by the gravitational potential energy change (GPEC method) of an extremity from the heart level. Delta DPG which was characteristic of stability, discrimination and low speed record by modified devices was applied for the experiments including postural, static and dynamic exercises. Room temperature during experiments was kept constant. The Delta DPG-P wave amplitude in maximal elevation of upper and lower extremities (mean±S. D., n) increased to 162.3±33.5% (38) and 176.7±33.4% (12), respectively, and that in maximal lowering of upper and lower extremities decreased to 36.9±10.5% (35) and 37.5±12.6% (15), respectively. These data reveal that the GPEC method may be useful for the determination of arteriolar sensitivity in humans.