To test whether changes in oxygenation of a resting skeletal muscle, evoked by a static contraction in a contralateral muscle, is uniform within a given skeletal muscle, we used near-infrared spectroscopy (NIRS). Seven subjects performed 2 min static knee extension exercise at 30% of maximal voluntary contraction. Changes in oxygenated hemoglobin (HbO2) were monitored using multiple-channel NIRS (40 channels, 13 sources and 12 detectors) attached on the contralateral nonexercising triceps surae muscle. Changes in HbO2 were expressed as a percentage of total labile signals. To characterize the distribution of changes in HbO2, channels were compared between their positions on the triceps surae muscle, and represented as 'proximal versus distal' and 'lateral versus medial' portions. During static muscle contraction, the averaged changes in HbO2 of all channels were correlated with those in calf blood flow (plethysmography; R2=0.188, P<0.05) and with calf vascular conductance (R2=0.146, P< 0.05). HbO2 did not differ significantly between the lateral and medial portions of the triceps surae muscle. In contrast, the decrease of HbO2 in the proximal portion of the muscle was greater than that of the distal portion (P< 0.05). These results indicate that the changes in oxygenation of a resting muscle, evoked by static contraction of the contralateral muscle, are heterogeneous.
- Near-infrared spectroscopy
- Sympathetic nerve activity
ASJC Scopus subject areas
- Orthopedics and Sports Medicine
- Public Health, Environmental and Occupational Health
- Physiology (medical)