Association between regional quadriceps oxygenation and blood oxygen saturation during normoxic one-legged dynamic knee extension

It is not clear whether muscle oxygenation (O_2-NIRS) measured by near-infrared spectroscopy (NIRS) correlates with femoral venous SO₂ (S_fvo₂) during normoxic exercise. Therefore, the purpose of this study was to compare physiologically calibrated O_2-NIRS with S_fvo₂ in subjects performing one-legged dynamic knee extension exercise (1L-KEE). Five healthy male subjects (age 25±2 year, height 177.8±4.8 cm, body weight 67.1 ± 5.0 kg; mean ± SD) performed 1L-KEE at 20, 40, and 60% of peak work rate (WR-peak) each for 4 min. S_fvo₂ was measured at rest and during the 3rd minute of each work rate. O_2-NIRS was continuously monitored in a proximal region of the vastus lateralis (VL-p), a distal region of VL (VL-d), and a proximal region of the rectus femoris (RF-p). S_fvo₂ was 56.0% at rest and decreased to 36.6 at 20% WR-peak, 35.8 at 40% WR-peak, and 31.1 at 60% WR-peak. There was a significant correlation between O_2-NIRS and S_fvo₂(VL-p: r ² = 0.62, VL-d: r ² = 0.35, RF-p: r ² = 0.62, with a moderate variation among individuals at each site; residual values = 4.83 – 11.75). These data indicate that NIRS measurement provides a reflection of S_fvo₂ during 20–60% WR-peak of normoxic 1L-KEE.