Muscle Oxygenation During Running Assessed by Broad Band NIRS.

We used spatially resolved near-infrared spectroscopy (SRS-NIRS) to assess calf and thigh muscle oxygenation during running on a motor-driven treadmill. Two protocols were used: An incremental speed protocol was performed in 5-min stages, while a pacing paradigm modulated the step frequency (2.3 Hz [SLow]; 3.3 Hz [SHigh]) during a constant velocity for 2 min each. A SRS-NIRS broadband system was used to measure total haemoglobin concentration and oxygen saturation (SO2). An accelerometer was placed on the hip joints to measure limb acceleration through the experiment. The data showed that the calf desaturated to a significantly lower level than the thigh. During the pacing protocol, SO2 was significantly different between the high and low step frequencies. Additionally, physiological data as measured by spirometry were different between the SLow vs. SHigh pacing trials. Significant differences in VO2 at the same workload (speed) indicate alterations in mechanical efficiency. These data suggest that SRS broadband NIRS can be used to discern small changes in muscle oxygenation, making this device useful for metabolic exercise studies in addition to spirometry and movement monitoring by accelerometers.